Professor (Research), Psychiatry & Behavioral Science - Sleep Center
The research focus of the Sleep and Circadian Neurobiology (SCN) Laboratory is the study of the sleep and circadian physiology using various animal models. A portion of the research is carried out using rodent models of narcolepsy and circadian rhythm sleep disorders. The laboratory also carries out pharmacological studies aiming to develop new treatments for these sleep disorders.
Central nervous system (CNS) histamine is low in individuals with narcolepsy, a disease characterized by severe fragmentation of both sleep and wake. We have developed a primate model, the squirrel monkey, with which we can examine the role of the CNS in the wake-consolidation process, as these primates are day-active, have consolidated wake and sleep and have cerebrospinal fluid (CSF) that is readily accessible. Using this model and three distinct protocols, we report herein on the role of CNS histamine in the wake consolidation process. CSF histamine has a robust daily rhythm, with a mean of 24.9?±?3.29?pg?mL(-1) , amplitude of 31.7?±?6.46?pg?mL(-1) and a peak at 17:49?± 70.3?min (lights on 07:00-19:00?hours). These levels are not significantly affected by increases (up to 161?±?40.4% of baseline) or decreases (up to 17.2?±?2.50% of baseline) in locomotion. In direct contrast to the effects of sleep deprivation in non-wake-consolidating mammals, in whom CSF histamine increases, pharmacologically induced sleep (?-hydroxybutyrate) and wake (modafinil) have no direct effects on CSF histamine concentrations. These data indicate that the time-course of histamine in CSF in the wake-consolidated squirrel monkey is robust against variation in activity and sleep and wake-promoting pharmacological compounds, and may indicate that histamine physiology plays a role in wake-consolidation such as is present in the squirrel monkey and humans.
View details for DOI 10.1111/j.1365-2869.2011.00957.x
View details for Web of Science ID 000301931500010
View details for PubMedID 21910776
Monogenic neurodevelopmental disorders provide key insights into the pathogenesis of disease and help us understand how specific genes control the development of the human brain. Timothy syndrome is caused by a missense mutation in the L-type calcium channel Ca(v)1.2 that is associated with developmental delay and autism. We generated cortical neuronal precursor cells and neurons from induced pluripotent stem cells derived from individuals with Timothy syndrome. Cells from these individuals have defects in calcium (Ca(2+)) signaling and activity-dependent gene expression. They also show abnormalities in differentiation, including decreased expression of genes that are expressed in lower cortical layers and in callosal projection neurons. In addition, neurons derived from individuals with Timothy syndrome show abnormal expression of tyrosine hydroxylase and increased production of norepinephrine and dopamine. This phenotype can be reversed by treatment with roscovitine, a cyclin-dependent kinase inhibitor and atypical L-type-channel blocker. These findings provide strong evidence that Ca(v)1.2 regulates the differentiation of cortical neurons in humans and offer new insights into the causes of autism in individuals with Timothy syndrome.
View details for DOI 10.1038/nm.2576
View details for Web of Science ID 000297978000039
View details for PubMedID 22120178
Narcolepsy is a chronic sleep disorder, characterized by excessive daytime sleepiness (EDS), cataplexy, sleep paralysis and hypnagogic hallucinations. Both sporadic (95%) and familial (5%) forms of narcolepsy exist in humans. The major pathophysiology of human narcolepsy has been recently discovered based on the discovery of narcolepsy genes in animals; the genes involved in the pathology of the hypocretin/orexin ligand and its receptor. Mutations in hypocretin-related genes are rare in humans, but hypocretin ligand deficiency is found in a large majority of narcolepsy with cataplexy. Hypocretin ligand deficiency in human narcolepsy is probably due to the post-natal cell death of hypocretin neurones. Although a close association between human leucocyte antigen (HLA) and human narcolepsy with cataplexy suggests an involvement of autoimmune mechanisms, this has not yet been proved. Hypocretin deficiency is also found in symptomatic cases of narcolepsy and EDS with various neurological conditions, including immune-mediated neurological disorders, such as Guillain-Barre syndrome, MA2-positive paraneoplastic syndrome and neuromyelitis optica (NMO)-related disorder. The findings in symptomatic narcoleptic cases may have significant clinical relevance to the understanding of the mechanisms of hypocretin cell death and choice of treatment option. The discoveries in human cases lead to the establishment of the new diagnostic test of narcolepsy (i.e. low cerebrospinal fluid hypocretin-1 levels for 'narcolepsy with cataplexy' and 'narcolepsy due to medical condition'). As a large majority of human narcolepsy patients are ligand deficient, hypocretin replacement therapy may be a promising new therapeutic option, and animal experiments using gene therapy and cell transplantations are in progress.
View details for DOI 10.1111/j.1748-1716.2009.02012.x
View details for Web of Science ID 000274147900004
View details for PubMedID 19555382
Amyloid-beta (Abeta) accumulation in the brain extracellular space is a hallmark of Alzheimer's disease. The factors regulating this process are only partly understood. Abeta aggregation is a concentration-dependent process that is likely responsive to changes in brain interstitial fluid (ISF) levels of Abeta. Using in vivo microdialysis in mice, we found that the amount of ISF Abeta correlated with wakefulness. The amount of ISF Abeta also significantly increased during acute sleep deprivation and during orexin infusion, but decreased with infusion of a dual orexin receptor antagonist. Chronic sleep restriction significantly increased, and a dual orexin receptor antagonist decreased, Abeta plaque formation in amyloid precursor protein transgenic mice. Thus, the sleep-wake cycle and orexin may play a role in the pathogenesis of Alzheimer's disease.
View details for DOI 10.1126/science.1180962
View details for Web of Science ID 000271712300043
View details for PubMedID 19779148
The orexin-producing neurons are hypothesized to be essential for the circadian control of sleep/wake behavior, but it remains unknown whether these rhythms are mediated by the orexin peptides or by other signaling molecules released by these neurons such as glutamate or dynorphin. To determine the roles of these neurotransmitters, we examined the circadian rhythms of sleep/wake behavior in mice lacking the orexin neurons (ataxin-3 [Atx] mice) and mice lacking just the orexin neuropeptides (orexin knockout [KO] mice).We instrumented mice for recordings of sleep-wake behavior, locomotor activity (LMA), and body temperature (Tb) and recorded behavior after 6 days in constant darkness.The amplitude of the rapid eye movement (REM) sleep rhythm was substantially reduced in Atx mice but preserved in orexin KO mice. This blunted rhythm in Atx mice was caused by an increase in the amount of REM sleep during the subjective night (active period) due to more transitions into REM sleep and longer REM sleep episodes. In contrast, the circadian variations of Tb, LMA, Wake, non-REM sleep, and cataplexy were normal, suggesting that the circadian timekeeping system and other output pathways are intact in both Atx and KO mice.These results indicate that the orexin neurons are necessary for the circadian suppression of REM sleep. Blunting of the REM sleep rhythm in Atx mice but not in orexin KO mice suggests that other signaling molecules such as dynorphin or glutamate may act in concert with orexins to suppress REM sleep during the active period.
View details for Web of Science ID 000269469700004
View details for PubMedID 19750917
Sleep deprivation can impair human health and performance. Habitual total sleep time and homeostatic sleep response to sleep deprivation are quantitative traits in humans. Genetic loci for these traits have been identified in model organisms, but none of these potential animal models have a corresponding human genotype and phenotype. We have identified a mutation in a transcriptional repressor (hDEC2-P385R) that is associated with a human short sleep phenotype. Activity profiles and sleep recordings of transgenic mice carrying this mutation showed increased vigilance time and less sleep time than control mice in a zeitgeber time- and sleep deprivation-dependent manner. These mice represent a model of human sleep homeostasis that provides an opportunity to probe the effect of sleep on human physical and mental health.
View details for DOI 10.1126/science.1174443
View details for Web of Science ID 000269242400044
View details for PubMedID 19679812
To create operational criteria for polygraphic assessments of direct transitions from wake to REM sleep (DREM), as a murine analog of human cataplexy, we have analyzed DREM episodes in congenic lines of orexin/ataxin-3 transgenic [TG] mice and wild-type littermates. The sleep stage of each 10-second epoch was visually scored using our standard criteria. Specificity of DREM for narcoleptic TG mice and sensitivity to detect DREM was evaluated using different DREM criteria. We found that DREM transitions by 10-second epoch scoring are not specific for narcoleptic TG mice and also occur in WT mice during light period. These wake-to-REM transitions in WT mice (also seen in TG mice during light period) were characteristically different from DREM transitions in TG mice during dark period; they tended to occur as brief bouts of wakefulness interrupting extended episodes of REM sleep, suggesting that these transitions do not represent abnormal manifestations of REM sleep. We therefore defined the DREM transitions by requiring a minimum number of preceding wake epochs. Requiring no fewer than four consecutive epochs of wakefulness produced the best combination of specificity (95.9%) and sensitivity (66.0%). By definition, DREM in dark-period is 100% specific to narcolepsy and was 95.9% specific overall. In addition, we found that desipramine, a trycyclic anticataplectic, potently reduces DREM, while two wake-promoting compounds have moderate (D-amphetamine) and no (modafinil) effect on DREM; the effects mirror the anticataplectic effects of these compounds reported in canine and human narcolepsy. Our definition of DREM in murine narcolepsy may provide good electrophysiological measures for cataplexy-equivalent episodes.
View details for DOI 10.1016/j.expneurol.2009.01.015
View details for Web of Science ID 000265859000007
View details for PubMedID 19416673
To examine whether cerebrospinal fluid (CSF) histamine contents are altered in human narcolepsy and whether these alterations are specific to hypocretin deficiency, as defined by low CSF hypocretin-1.Patients meeting the ICSD-2 criteria for narcolepsy with and without cataplexy and who had CSF hypocretin-1 results available were selected from the Stanford Narcolepsy Database on the basis of CSF availability and adequate age and sex matching across 3 groups: narcolepsy with low CSF hypocretin-1 (n=34, 100% with cataplexy), narcolepsy without low CSF hypocretin-1 (n=24, 75% with cataplexy), and normal controls (n=23). Low CSF hypocretin-1 was defined as CSF < or =110 pg/mL (1/3 of mean control values). Six of 34 patients with low CSF hypocretin-1, six of 24 subjects with normal CSF hypocretin-1, and all controls were unmedicated at the time of CSF collection. CSF histamine was measured in all samples using a fluorometric HPLC system.Mean CSF histamine levels were: 133.2 +/- 20.1 pg/mL in narcoleptic subjects with low CSF hypocretin-1, 233.3 +/- 46.5 pg/mL in patients with normal CSF hypocretin-1 (204.9 +/- 89.7 pg/mL if only patients without cataplexy are included), and 300.5 +/- 49.7 pg/mL in controls, reaching statistically significant differences between the 3 groups.CSF histamine levels are reduced in human narcolepsy. The reduction of CSF histamine levels was more evident in the cases with low CSF hypocretin-1, and levels were intermediate in other narcolepsy cases. As histamine is a wake-promoting amine known to decrease during sleep, decreased histamine could either passively reflect or partially mediate daytime sleepiness in these pathologies.
View details for Web of Science ID 000262890300008
View details for PubMedID 19238804
To (1) replicate our prior result of low cerebrospinal fluid (CSF) histamine levels in human narcolepsy in a different sample population and to (2) evaluate if histamine contents are altered in other types of hypersomnia with and without hypocretin deficiency.Cross sectional studies.Sixty-seven narcolepsy subjects, 26 idiopathic hypersomnia (IHS) subjects, 16 obstructive sleep apnea syndrome (OSAS) subjects, and 73 neurological controls were included. All patients were Japanese. Diagnoses were made according to ICSD-2.We found significant reductions in CSF histamine levels in hypocretin deficient narcolepsy with cataplexy (mean +/- SEM; 176.0 +/- 25.8 pg/mL), hypocretin non-deficient narcolepsy with cataplexy (97.8 +/- 38.4 pg/mL), hypocretin non-deficient narcolepsy without cataplexy (113.6 +/- 16.4 pg/mL), and idiopathic hypersomnia (161.0 +/- 29.3 pg/ mL); the levels in OSAS (259.3 +/- 46.6 pg/mL) did not statistically differ from those in the controls (333.8 +/- 22.0 pg/mL). Low CSF histamine levels were mostly observed in non-medicated patients; significant reductions in histamine levels were evident in non-medicated patients with hypocretin deficient narcolepsy with cataplexy (112.1 +/- 16.3 pg/ mL) and idiopathic hypersomnia (143.3 +/- 28.8 pg/mL), while the levels in the medicated patients were in the normal range.The study confirmed reduced CSF histamine levels in hypocretin-deficient narcolepsy with cataplexy. Similar degrees of reduction were also observed in hypocretin non-deficient narcolepsy and in idiopathic hypersomnia, while those in OSAS (non central nervous system hypersomnia) were not altered. The decrease in histamine in these subjects were more specifically observed in non-medicated subjects, suggesting CSF histamine is a biomarker reflecting the degree of hypersomnia of central origin.
View details for Web of Science ID 000262890300009
View details for PubMedID 19238805
Sleepiness and inattention caused by sleep and circadian rhythm disorders or inadequate sleep habits adversely affect workers in many industries as well as the general public, and these disorders are likely to lead to public health and safety problems and adversely affect civilian life. Evidence is accumulating that these sleep related problems are contributing factors not only in many errors of judgement and accidents, but also related to some highly prevalent diseases, such as diabetes, obesity and hypertension. For each of these societal concerns, sleep science must be translated to the general public and to those in policy positions for improving public policy and public health awareness. In the United State, the National Commission for Sleep Disorders Research (established by the US Congress in 1998) completed a comprehensive report of its findings in 1993 to address these problems. The commission estimated that sleep disorders and sleepiness cost the United States $50 billion and called for permanent and concentrated efforts in expanding basic and clinical research on sleep disorders as well as in improving public awareness of the dangers of inadequate sleep hygiene. As a result of these efforts, the number of sleep centers has increased steadily and the total of the NIH (National Institutes of Health) funding for sleep research has also grown. In response to this progress in the US (together with appeals by Japanese Sleep Specialists), the Science Council of Japan published "The Recommendation of Creation of Sleep Science and Progression of Research" in 2002. In this article, we introduce and detail to the Japanese readers the US Government's efforts focusing on the report of the National Commission for Sleep Disorders Research, and we believe that the US Government's effort is a good example for the Japanese society to follow.
View details for PubMedID 18783014
To determine whether hypocretin receptor gene (hcrtR1 and hcrtR2) expression is affected after long-term hypocretin ligand loss in humans and animal models of narcolepsy.Animal and human study. We measured hcrtR1 and hcrtR2 expression in the frontal cortex and pons using the RT-PCR method in murine models (8-week-old and 27-week-old orexin/ataxin-3 transgenic (TG) hypocretin cell ablated mice and wild-type mice from the same litter, 10 mice for each group), in canine models (8 genetically narcoleptic Dobermans with null mutations in the hcrtR2, 9 control Dobermans, 3 sporadic ligand-deficient narcoleptics, and 4 small breed controls), and in humans (5 narcolepsy-cataplexy patients with hypocretin deficiency (average age 77.0 years) and 5 control subjects (72.6 years).27-week-old (but not 8-week-old) TG mice showed significant decreases in hcrtR1 expression, suggesting the influence of the long-term ligand loss on the receptor expression. Both sporadic narcoleptic dogs and human narcolepsy-cataplexy subjects showed a significant decrease in hcrtR1 expression, while declines in hcrtR2 expression were not significant in these cases. HcrtR2-mutated narcoleptic Dobermans (with normal ligand production) showed no alteration in hcrtR1 expression.Moderate declines in hcrtR expressions, possibly due to long-term postnatal loss of ligand production, were observed in hypocretin-ligand deficient narcoleptic subjects. These declines are not likely to be progressive and complete. The relative preservation of hcrtR2 expression also suggests that hypocretin based therapies are likely to be a viable therapeutic options in human narcolepsy-cataplexy.
View details for Web of Science ID 000258111000009
View details for PubMedID 18714784
Armodafinil is the (R)-enantiomer of the wakepromoting compound modafinil (racemic), with a considerably longer half-life of 10-15 hours. Armodafinil (developed by Cephalon, Frazer, PA, USA) was approved in June 2007 for the treatment of excessive sleepiness associated with narcolepsy, obstructive sleep apnea syndrome and shift work disorder, and the indications are the same as those for modafinil. Like modafinil, the mechanisms of action of armodafinil are not fully characterized and are under debate. Clinical trials in these sleep disorders demonstrated an enhanced efficacy for wake promotion (wake sustained for a longer time period using doses lower than those of modafinil). The safety profile is consistent with that of modafinil, and armodafinil is well tolerated by the patients. Like modafinil, armodafinil is classified as a non-narcotic Schedule IV compound. Many patients with excessive sleepiness may prefer the longer duration of effect and may have better compliance (with low doses) with armodafinil. The commercial challenge to armodafinil may come from generic modafinil, which may become available in 2012, as well as from classical amphetamine and amphetamine-like compounds (for the treatment of narcolepsy).
View details for DOI 10.1358/dot.2008.44.5.1195861
View details for Web of Science ID 000257604100001
View details for PubMedID 18596995
Down syndrome is characterized by a host of behavioral abnormalities including sleep disturbances. Sleep and EEG was studied at the age of 3 months in two mouse models of the condition, Ts65Dn and Ts1Cje, carrying one extra copy of partially overlapping segments of the mmu chromosome 16 (equivalent to the human chromosome 21). We found that the Ts65Dn mice showed increased waking amounts at the expense of non-REM sleep, increased theta power during sleep and a delayed sleep rebound after sleep deprivation. In contrast, Ts1Cje had limited sleep and EEG abnormalities, showing only a delayed sleep rebound after sleep deprivation and no difference in theta power. We previously found that mice over-expressing the human APPwt transgene, a gene triplicated in Ts65Dn but not Ts1Cje, also show increased wake and theta power during sleep. These results demonstrate abnormalities in sleep and EEG in Ts65Dn mice and underscore a possible correlation between App overexpression and hippocampal theta oscillations.
View details for DOI 10.1016/j.nbd.2007.07.014
View details for Web of Science ID 000254665100001
View details for PubMedID 18282758
Reduced cerebrospinal fluid (CSF) histamine levels were found in human hypersomnia. To evaluate the functional significance of changes in CSF histamine levels, we measured the levels in rats across 24h, after the administration of wake-promoting compounds modafinil, amphetamine, and thioperamide, and after sleep deprivation and food deprivation. Thioperamide significantly increased CSF histamine levels with little effects on locomotor activation. Both modafinil and amphetamine markedly increased the locomotor activity, but had no effects on histamine. The levels are high during active period and are markedly elevated by sleep deprivation, but not by food deprivation. Our study suggests that CSF histamine levels in rats reflect the central histamine neurotransmission and vigilance state changes, providing deeper insight into the human data.
View details for DOI 10.1016/j.neulet.2007.11.002
View details for Web of Science ID 000253071800008
View details for PubMedID 18077091
The hypocretins (also known as orexins) and their receptors are the focus of many investigators as sites for therapeutic intervention in a number of endocrinologic, neurologic and sleep disorders. The interest for the hypocretin system is highlighted by a recent discovery that a human sleep disorder, narcolepsy, is tightly linked with the deficiency of hypocretin peptides. This finding suggests that hypocretin replacement is a promising new therapeutic intervention for human narcolepsy and related disorders, but this will only become possible when small-molecule (i.e., non-peptide) hypocretin receptor agonists become available. In contrast, high-throughput screening efforts in hypocretin receptor drug discovery programs by a number of pharmaceutical companies have already identified novel small-molecule hypocretin receptor antagonists and these antagonists may be used for the treatment of insomnia, especially for sleep-initiation problems. This is because hypocretin-deficient narcoleptic subjects show very short sleep latency and the blockade of the hypocretin receptor may induce a similar sleep symptom. At least two hypocretin receptor antagonists (ACT-078573 and GW-649868) are presently under development for the treatment of human insomnia and the promising aspects and limitations of these therapeutic interventions are discussed in this paper.
View details for DOI 10.1517/135437220.127.116.115
View details for Web of Science ID 000251117000004
View details for PubMedID 17970638
Using forward and reverse genetics, the genes (hypocretin/orexin ligand and its receptor) involved in the pathogenesis of the sleep disorder, narcolepsy, in animals, have been identified. Mutations in hypocretin related-genes are extremely rare in humans, but hypocretin-ligand deficiency is found in most narcolepsy-cataplexy cases. Hypocretin deficiency in humans can be clinically detected by CSF hypocretin-1 measures, and undetectably low CSF hypocretin-1 is now included in the revised international diagnostic criteria of narcolepsy. Since hypocretin-ligand deficiency is the major pathophysiology in human narcolepsy, hypocretin replacements (using hypocretin agonists or gene therapy) are promising future therapeutic options. New insights into the roles of hypocretin system on sleep physiology have also rapidly increased. Hypocretins are involved in various fundamental hypothalamic functions such as feeding, energy homeostasis and neuroendocrine regulation. Hypocretin neurons project to most ascending arousal systems (including monoaminergic and cholinergic systems), and generally exhibit excitatory inputs. Together with the recent finding of the sleep promoting system in the hypothalamus (especially in the GABA/galanin ventrolateral preoptic area which exhibits inhibitory inputs to these ascending systems), the hypothalamus is now recognized as the most important brain site for the sleep switch, and other peptidergic systems may also participate in this regulation. Meanwhile, narcolepsy now appears to be a more complex condition than previously thought. The pathophysiology of the disease is involved in the abnormalities of sleep and various hypothalamic functions due to hypocretin deficiency, such as the changes in energy homeostasis, stress reactions and rewarding. Narcolepsy is therefore, an important model to study the link between sleep regulation and other fundamental hypothalamic functions.
View details for DOI 10.1016/j.npep.2007.01.003
View details for Web of Science ID 000247040700001
View details for PubMedID 17376528
Narcolepsy is characterized by excessive daytime sleepiness (EDS), cataplexy and/or other dissociated manifestations of rapid eye movement (REM) sleep (hypnagogic hallucinations and sleep paralysis). Narcolepsy is currently treated with amphetamine-like central nervous system (CNS) stimulants (for EDS) and antidepressants (for cataplexy). Some other classes of compounds such as modafinil (a non-amphetamine wake-promoting compound for EDS) and gamma-hydroxybutyrate (GHB, a short-acting sedative for EDS/fragmented nighttime sleep and cataplexy) given at night are also employed. The major pathophysiology of human narcolepsy has been recently elucidated based on the discovery of narcolepsy genes in animals. Using forward (i.e., positional cloning in canine narcolepsy) and reverse (i.e., mouse gene knockout) genetics, the genes involved in the pathogenesis of narcolepsy (hypocretin/orexin ligand and its receptor) in animals have been identified. Hypocretins/orexins are novel hypothalamic neuropeptides also involved in various hypothalamic functions such as energy homeostasis and neuroendocrine functions. Mutations in hypocretin-related genes are rare in humans, but hypocretin-ligand deficiency is found in many narcolepsy-cataplexy cases. In this review, the clinical, pathophysiological and pharmacological aspects of narcolepsy are discussed.
View details for DOI 10.1016/j.sleep.2007.03.008
View details for Web of Science ID 000247230800007
View details for PubMedID 17470414
Recent population studies have identified important interrelationships between sleep duration and body weight regulation. The hypothalamic hypocretin/orexin neuropeptide system is able to influence each of these. Disruption of the hypocretin system, such as occurs in narcolepsy, leads to a disruption of sleep and is often associated with increased body mass index. We examined the potential interrelationship between the hypocretin system, metabolism and sleep by measuring locomotion, feeding, drinking, body temperature, sleep/wake and energy metabolism in a mouse model of narcolepsy (ataxin-ablation of hypocretin-expressing neurons). We found that locomotion, feeding, drinking and energy expenditure were significantly reduced in the narcoleptic mice. These mice also exhibited severe sleep/wake fragmentation. Upon awakening, transgenic and control mice displayed a similar rate of increase in locomotion and food/water intake with time. A lack of long wake episodes partially or entirely explains observed differences in overall locomotion, feeding and drinking in these transgenic mice. Like other parameters, energy expenditure also rose and fell depending on the sleep/wake status. Unlike other parameters, however, energy expenditure in control mice increased upon awakening at a greater rate than in the narcoleptic mice. We conclude that the profound sleep/wake fragmentation is a leading cause of the reduced locomotion, feeding, drinking and energy expenditure in the narcoleptic mice under unperturbed conditions. We also identify an intrinsic role of the hypocretin system in energy expenditure that may not be dependent on sleep/wake regulation, locomotion, or food intake. This investigation illustrates the need for coordinated study of multiple phenotypes in mouse models with altered sleep/wake patterns.
View details for DOI 10.1113/jphysiol.2007.129510
View details for Web of Science ID 000246756000022
View details for PubMedID 17379635
Sleep disorders are disturbances of usual sleep patterns or behaviors caused by deregulation of neuronal synchronicity and of the balance of the neurotransmitter system involved in sleep regulation. Insomnia and hypersomnia are frequent sleep disorders, and these are most often treated pharmacologically with hypnotics and wake-promoting compounds. These compounds act on classical neurotransmitter systems, such as benzodiazepines on gamma amino butyric acid (GABA)(A) receptors, and amphetamine-like stimulants on monoaminergic terminals to modulate neurotransmission. In addition, acetylcholine, amino acids, lipids and proteins (cytokines) and peptides, are known to significantly modulate sleep, and thus, are possibly involved in the pathophysiology of some sleep disorders. Due to recent developments in molecular biological techniques, many neuropeptides have been newly identified, and some are found to significantly modulate sleep. Recent discoveries also include the finding that the impairment of hypocretin/orexin neurotransmission (a recently isolated hypothalamic neuropeptide and receptor system), is the major pathophysiology of narcolepsy with cataplexy. A hypocretin replacement therapy is anticipated to reverse the disease symptoms in humans. In this article, we will review the history of neuropeptide research, sleep modulatory effects of various neuropeptides, and the general strategies for the pharmacological therapeutics targeting the peptidergic systems by referring to hypocretin-deficient narcolepsy as an immediate example.
View details for PubMedID 17305553
Insomnia and hypersomnia are frequent sleep disorders, and they are most often treated pharmacologically with hypnotics and wake-promoting compounds. These compounds act on classical neurotransmitter systems, such as benzodiazepines on GABA-A receptors, and amfetamine-like stimulants on monoaminergic terminals to modulate neurotransmission. In addition, acetylcholine, amino acids, lipids and proteins (cytokines) and peptides, are known to significantly modulate sleep and are, therefore, possibly involved in the pathophysiology of some sleep disorders. Due to the recent developments of molecular biological techniques, many neuropeptides have been newly identified, and some are found to significantly modulate sleep. It was also discovered that the impairment of the hypocretin/orexin neurotransmission (a recently isolated hypothalamic neuropeptide system) is the major pathophysiology of narcolepsy, and hypocretin replacement therapy is anticipated to treat the disease in humans. In this article, the authors briefly review the history of neuropeptide research, followed by the sleep modulatory effects of various neuropeptides. Finally, general strategies for the pharmacological therapeutics targeting the peptidergic systems for sleep disorders are discussed.
View details for DOI 10.1517/1472818.104.22.168
View details for Web of Science ID 000243300800005
View details for PubMedID 17150033
Narcolepsy, which affects 1 in 2000 people in the general population, is characterized by excessive daytime sleepiness (EDS), cataplexy, and other dissociated manifestations of rapid eye movement sleep (hypnagogic hallucinations and sleep paralysis). The disease is currently treated with amphetamine-like central nervous system stimulants (for EDS) and antidepressants (for cataplexy). Some compounds from other classes, such as modafinil (a non-amphetamine wake-promoting compound for EDS) and sodium oxybate (a short-acting sedative for EDS and cataplexy, administered at night), are also employed. The major pathophysiology of human narcolepsy has recently been revealed by the extension of discoveries of narcolepsy genes in animal models: hypocretin/orexin ligand deficiency has been shown in about 90% of human narcolepsy-cataplexy. This finding led directly to the development of new diagnostic tests (i.e., cerebrospinal fluid hypocretin measures). Hypocretin replacement is also likely to be a new therapeutic option for hypocretin-deficient narcolepsy, but is still not available in humans. In this review, the pharmacologic and pathophysiologic aspects of narcolepsy are discussed.
View details for Web of Science ID 000251940000003
View details for PubMedID 18078360
The importance of the lateral hypothalamus in the regulation of reward and motivation has long been recognized. However, the neuronal network involved in such a hypothalamic regulation of reward remains essentially unknown. Recently, hypocretin-containing neurons, a group of hypothalamic neurons known to be associated with the stability of arousal, have emerged as important structures in the control of brain reward function. This review summarizes a Mini-Symposium presented at the 2006 Annual Meeting of the Society for Neuroscience.
View details for DOI 10.1523/JNEUROSCI.3118-06.2006
View details for Web of Science ID 000241192800008
View details for PubMedID 17035520
Recent studies in human and animal models of narcolepsy have suggested that obesity in narcolepsy may be due to deficiency of hypocretin signaling, and is also under the influence of environmental factors and the genetic background. In the current study, using two hypocretin/orexin deficient narcoleptic mouse models (i.e. preproorexin knockout (KO) and orexin/ataxin-3 transgenic (TG) mice) with cross-sectional assessments, we have further analyzed factors affecting obesity. We found that both KO and TG narcoleptic mice with mixed genetic backgrounds (N4-5, 93.75-96.88% genetic composition of C57BL/6) tended to be heavier than wild type (WT) mice of 100-200 days old. The body weight of heterozygous mice was intermediate between those of KO and WT mice. Obesity was more prominent in females in both KO and TG narcoleptic mice and was associated with higher serum leptin levels, suggesting a partial leptin resistance. Obesity is less prominent in the congenic TG narcoleptic mice, but is still evident in females. Our results confirmed that hypocretin/orexin ligand deficiency is one of the critical factors for the obese tendency in narcolepsy. However, multiple factors are also likely to affect this phenotype, and a sex difference specific alteration of leptin-hypocretin signaling may be involved.
View details for DOI 10.1016/j.peptides.2006.03.011
View details for Web of Science ID 000240379800037
View details for PubMedID 16626839
To determine if hypocretin deficiency is associated with abnormally low serum leptin levels, a putative cause of increased body mass index in narcoleptics.Cross-sectional controlled study.Three hundred seventy subjects, including 111 healthy controls, 93 narcoleptic subjects with hypocretin deficiency (cerebrospinal fluid [CSF] hypocretin-1 levels < 110 pg/mL), 72 narcoleptic subjects with normal hypocretin levels, and 89 subjects with other sleep disordersAfter completing the Stanford Sleepiness Inventory, participants underwent spinal taps and blood sampling for measurement of CSF leptin and hypocretin-1 levels, HLA DQB1*0602 phenotyping, and serum leptin and C-reactive protein levels.Serum leptin levels were similar in narcoleptic subjects, whether hypocretin-deficient (13.2 +/- 1.7 ng/mL, mean +/- SEM) or not (13.0 +/- 1.8 ng/mL), controls (10.1 +/- 1.1 ng/mL) and subjects with other sleep disorders (11.5 +/- 1.6 ng/mL). Similarly, the CSF leptin levels and the CSF: serum leptin ratios (an indicator of brain leptin uptake) were not different between groups. Serum and CSF leptin levels were higher in women and in subjects with higher body mass indexes. Leptin brain uptake decreased in women, in the aged, and in more-obese subjects. In contrast with a presumed inhibitory effect of leptin on hypocretin-containing cells, CSF leptin levels tended to correlate positively with CSF hypocretin-1 levels. C-reactive protein was higher (4.2 +/- 0.9 mg/L) in narcoleptic subjects with hypocretin deficiency than in controls (1.4 +/- 0.3 mg/L, p = .0055), a difference still significant after adjustment on confounding factors.Our data do not support a role for leptin in mediating increased body mass index in narcolepsy. A moderate but selective increase in C-reactive protein in hypocretin-1 deficient subjects should prompt research on inflammation in narcolepsy.
View details for Web of Science ID 000240046400004
View details for PubMedID 16944669
Narcolepsy is characterized by excessive daytime sleepiness, cataplexy and other manifestations of dissociated rapid eye movement sleep. Narcolepsy is typically treated with amphetamine-like stimulants (sleepiness) and antidepressants (cataplexy). Newer compounds, such as modafinil (non-amphetamine wake-promoting compound for excessive daytime sleepiness) and sodium oxybate (short-acting sedative for fragmented nighttime sleep, cataplexy, excessive daytime sleepiness), are increasingly used. Recent discoveries indicate that the major pathophysiology of human narcolepsy is the loss of lateral hypothalamic neurons that produce the neuropeptide hypocretin (orexin). Approximately 90% of people diagnosed as having narcolepsy with cataplexy are hypocretin ligand deficient. This has led to the development of new diagnostic tests (cerebrospinal fluid hypocretin-1 measurements). Hypocretin receptor agonists are likely to be ideal therapeutic options for hypocretin-deficient narcolepsy but such compounds are still not available in humans.
View details for DOI 10.1016/j.tips.2006.05.006
View details for Web of Science ID 000239368900005
View details for PubMedID 16766052
Intracerebroventricular (ICV) or PVN local injections of oxytocin induce yawning and penile erection, for which a positive feedback mechanism for the PVN oxytocinergic activation is suggested, but this had not been directly substantiated in vivo. We have assessed the behavioral effects and activity of oxytocinergic neurons with double-staining for c-Fos and oxytocin in the PVN after ICV administration of oxytocin in adult male rats. ICV oxytocin injections (50 and 200 ng) dose-dependently induced yawning and penile erection and significantly increased the percentage of c-Fos positive oxytocin neurons in the medial, dorsal and lateral parvocellular subdivision of the PVN. However, increases in the magnocellular portion were not significant. We also found that lithium chloride (LiCl, 0.5 and l.0 mEq), a compound known to activate oxytocinergic neurons, also significantly increased the percentage of c-Fos positive oxytocin neurons in all PVN portions. However, LiCl did not induce yawning and penile erection, but counteracted the oxytocin-induced yawning and penile erection. These results suggest that if the activation of oxytocinergic neurons in the PVN is important for mediating oxytocin-induced yawning and penile erection, a selective activation of parvocellular oxytocinergic neurons in the PVN is likely to be involved.
View details for DOI 10.1016/j.neures.2005.12.005
View details for Web of Science ID 000236539200004
View details for PubMedID 16427151
Excessive daytime somnolence is a prevalent problem in medical practice and in society. It exacts a great toll in quality of life, personal and public safety, and productivity. The causes of EDS are myriad, and careful evaluation is needed to determine the cause in each case. Although much progress has been made in discovering the pathophysiology of narcolepsy, much more remains to be understood, and far less is known about other primary conditions of EDS. Several methods have been developed to assess EDS, although each of them has limitations. Treatment is available for the great majority of cases.
View details for DOI 10.1016/j.ncl.2005.08.002
View details for Web of Science ID 000233258100006
View details for PubMedID 16243614
Human narcolepsy is a chronic sleep disorder affecting 1:2000 individuals. The disease is characterized by excessive daytime sleepiness, cataplexy and other abnormal manifestations of REM sleep, such as sleep paralysis and hypnagogic hallucinations. Recently, it was discovered that the pathophysiology of (idiopathic) narcolepsy-cataplexy is linked to hypocretin ligand deficiency in the brain and cerebrospinal fluid (CSF), as well as the positivity of the human leukocyte antigen (HLA) DR2/DQ6 (DQB1*0602). The symptoms of narcolepsy can also occur during the course of other neurological conditions (i.e. symptomatic narcolepsy). We define symptomatic narcolepsy as those cases that meet the International Sleep Disorders Narcolepsy Criteria, and which are also associated with a significant underlying neurological disorder that accounts for excessive daytime sleepiness (EDS) and temporal associations. To date, we have counted 116 symptomatic cases of narcolepsy reported in literature. As, several authors previously reported, inherited disorders (n=38), tumors (n=33), and head trauma (n=19) are the three most frequent causes for symptomatic narcolepsy. Of the 116 cases, 10 are associated with multiple sclerosis, one case of acute disseminated encephalomyelitis, and relatively rare cases were reported with vascular disorders (n=6), encephalitis (n=4) and degeneration (n=1), and hererodegenerative disorder (three cases in a family). EDS without cataplexy or any REM sleep abnormalities is also often associated with these neurological conditions, and defined as symptomatic cases of EDS. Although it is difficult to rule out the comorbidity of idiopathic narcolepsy in some cases, review of the literature reveals numerous unquestionable cases of symptomatic narcolepsy. These include cases with HLA negative and/or late onset, and cases in which the occurrences of the narcoleptic symptoms are parallel with the rise and fall of the causative disease. A review of these cases (especially those with brain tumors), illustrates a clear picture that the hypothalamus is most often involved. Several cases of symptomatic cataplexy (without EDS) were also reported and in contrast, these cases appear to be often associated with non-hypothalamic structures. CSF hypocretin-1 measurement were also carried out in a limited number of symptomatic cases of narcolepsy/EDS, including narcolepsy/EDS associated with tumors (n=5), head trauma (n=3), vascular disorders (n=5), encephalopathies (n=3), degeneration (n=30), demyelinating disorder (n=7), genetic/congenital disorders (n=11) and others (n=2). Reduced CSF hypocretin-1 levels were seen in most symptomatic narcolepsy cases of EDS with various etiologies and EDS in these cases is sometimes reversible with an improvement of the causative neurological disorder and an improvement of the hypocretin status. It is also noted that some symptomatic EDS cases (with Parkinson diseases and the thalamic infarction) appeared, but they are not linked with hypocretin ligand deficiency. In contrast to idiopathic narcolepsy cases, an occurrence of cataplexy is not tightly associated with hypocretin ligand deficiency in symptomatic cases. Since CSF hypocretin measures are still experimental, cases with sleep abnormalities/cataplexy are habitually selected for CSF hypocretin measures. Therefore, it is still not known whether all or a large majority of cases with low CSF hypocretin-1 levels with CNS interventions, exhibit EDS/cataplexy. It appears that further studies of the involvement of the hypocretin system in symptomatic narcolepsy and EDS are helpful to understand the pathophysiological mechanisms for the occurrence of EDS and cataplexy.
View details for DOI 10.1016/j.smrv.2005.03.004
View details for Web of Science ID 000231170000005
View details for PubMedID 16006155
In the past, narcolepsy was primarily treated using amphetamine-like stimulants and tricyclic antidepressants. Newer and novel agents, such as the wake-promoting compound modafinil and more selective reuptake inhibitors targeting the adrenergic, dopaminergic, and/or serotoninergic reuptake sites (ie, venlafaxine, atomoxetine) are better-tolerated available alternatives. The development of these agents, together with sodium oxybate (a slow-wave sleep-enhancing agent that consolidates nocturnal sleep, reduces cataplexy, and improves sleepiness), has led to improved functioning and quality of life for many patients with the disorder. However, these treatments are all symptomatically based and do not target hypocretin, a major neurotransmitter involved in the pathophysiology of narcolepsy. In this review, we discuss emerging therapies in the area of narcolepsy. These include novel antidepressant or anticataplectic, wake-promoting, and hypnotic compounds. We also report on novel strategies designed to compensate for hypocretin deficiency and on the use of immunosupression at the time of narcolepsy onset.
View details for Web of Science ID 000229900500014
View details for PubMedID 16477963
Excessive daytime sleepiness (EDS) or somnolence is common in our patients and in society in general. The most common cause of EDS is "voluntary" sleep restriction. Other common causes include sleep-fragmenting disorders such as the obstructive sleep apnea syndrome. Somewhat less familiar to the clinician are EDS conditions arising from central nervous system dysfunction. Of these so-called primary disorders of somnolence, narcolepsy is the most well known and extensively studied, yet often misunderstood and misdiagnosed. Idiopathic hypersomnia, the recurrent hypersomnias, and EDS associated with nervous system disorders also must be well-understood to provide appropriate evaluation and management of the patient with EDS. This review summarizes the distinguishing features of these clinical syndromes of primary EDS. A brief overview of the pharmacological management of primary EDS is included. Finally, in view of the tremendous advances that have occurred in the past few years in our understanding of the pathophysiology of canine and human narcolepsy, we also highlight these discoveries.
View details for Web of Science ID 000224248200007
View details for PubMedID 15449220
Hypocretins (orexins) are involved in the sleep disorder narcolepsy. While hypocretin-1 has a daily oscillation, little is known regarding the relative contribution of circadian and homeostatic components on hypocretin release. The effect of lesions of the suprachiasmatic nucleus (SCN) on hypocretin-1 in the cerebrospinal fluid (CSF) was examined.SCN-ablated (SCNx) and sham-operated control rats were implanted with activity-temperature transmitters. Animals were housed individually under 1 of 3 lighting conditions: 12-hour:12-hour light:dark cycle (LD), constant light (LL), and constant darkness (DD). Lesions were verified histologically and shown not to affect hypocretin-containing cells. Hypocretin-1 concentrations in the CSF were determined every 4 hours using radioimmunoassays.Control animals displayed robust circadian (LL, DD) and diurnal (LD) fluctuations in CSF hypocretin-1, locomotor activity, and temperature. Peak CSF hypocretin-1 was at the end of the active period. Activity, temperature, and CSF hypocretin-1 were arrhythmic in SCNx animals in LL and DD. In LD, a weak but significant fluctuation in activity and temperature but not CSF hypocretin-1 was observed in SCNx animals. We also explored correlations between CSF hypocretin-1, CSF corticosterone, and locomotor activity occurring prior to CSF sampling in arrhythmic SCNx rats under constant conditions. Significant correlations between hypocretin-1 and activity were observed both across and within animals, suggesting that interindividual and time-of-the-day differences in activity have significant effects on hypocretin release in arrhythmic animals. No correlation was found between CSF hypocretin-1 and corticosterone.Hypocretin-1 release is under SCN control. Locomotor activity influences the activity of the hypocretin neurons.
View details for Web of Science ID 000223169300007
View details for PubMedID 15282996
Cataplexy, an emotion-triggered sudden loss of muscle tone specific to narcolepsy, is tightly associated with hypocretin deficiency. Using hypocretin receptor 2 gene (hcrtr 2)-mutated narcoleptic Dobermans, we have previously demonstrated that altered dopamine (DA) D(2/3) receptor mechanisms in mesencephalic DA nuclei are important for the induction of cataplexy. In the current study, we also found that the administration of D(2/3) agonists into diencephalic dopaminergic cell groups, including the area dorsal to the ventral tegmental area (DRVTA) and the periventricular gray (PVG) matter of the caudal thalamus (corresponding to area A11), significantly aggravated cataplexy in hcrtr 2-mutated narcoleptic Dobermans. A D(1) agonist and antagonist and a DA uptake inhibitor perfused into the DRVTA had no effect on cataplexy, suggesting an involvement of D(2/3) receptors located on DA cell bodies (i.e., autoreceptors) for the regulation of cataplexy. Because the A11 cell group projects to the spinal ventral horn, the A11 D(2/3) receptive mechanisms may directly modulate the activity of spinal motoneurons and modulate cataplexy.
View details for DOI 10.1016/j.nbd.2004.02.008
View details for Web of Science ID 000221365300029
View details for PubMedID 15207284
Using two different canine models of narcolepsy, we evaluated the therapeutic effects of hypocretin-1 on cataplexy and sleep.Intracerebroventricular administration of hypocretin-1 (10 and 30 nmol per dog) but not intravenous administration (up to 6 microg/kg) induced significant wakefulness in control dogs. However, hypocretin-1 had no effect on cataplexy or wakefulness in hypocretin receptor-2 gene (Hcrtr2) mutated narcoleptic Dobermans. Only very high intravenously doses of hypocretin-1 (96-384 microg/kg) penetrated the brain, to produce a short-lasting anticataplectic effect in a hypocretin-ligand-deficient animal.Hypocretin-1 administration, by central and systemic routes, does not improve narcoleptic symptoms in Hcrtr2 mutated Dobermans. Systemic hypocretin-1 hardly crosses the blood-brain barrier to produce therapeutic effects. The development of more centrally penetrable and longer lasting hypocretin analogs will be needed to further explore this therapeutic pathway in humans.
View details for Web of Science ID 000188205200008
View details for PubMedID 14746374
CSF hypocretin-1 was measured in 28 Guillain-Barré syndrome (GBS), 12 Miller-Fisher syndrome, 12 chronic inflammatory demyelinating polyneuropathy (CIDP), and 48 control subjects. Seven GBS subjects had undetectably low hypocretin-1 levels (<100 pg/mL). Hypocretin-1 levels were moderately reduced in an additional 11 GBS, 5 Miller-Fisher syndrome, and 1 CIDP subject. Low levels in GBS occurred early in the disease and were associated with upper CNS level abnormalities.
View details for Web of Science ID 000185460600020
View details for PubMedID 14504329
Different potencies for hypocretin-1 and -2 in sleep-wake regulation and feeding after intracerebroventricular (ICV) administration have been reported. These differences were often explained by the selectivity of the two hypocretins for hypocretin receptor-1 and -2, but little attention has been paid to kinetics of hypocretin peptides. We investigated the kinetics of the ICV hypocretin-1 and -2 in rats. ICV hypocretin-1 (10 nmol) increased hypocretin-1 peptide level in the CSF by 800-fold from baseline with the elevation lasting over 4 h. In contrast, after ICV hypocretin-2 (10 nmol), no significant rise in the CSF was found. CSF hypocretin levels were significantly correlated with the biological activities of CSF hypocretin-1 and -2 using the Ca(2+) mobilization assay. Difference in the kinetics of hypocretins should be considered for interpreting ICV effects of hypocretins.
View details for DOI 10.1016/S0304-3940(03)00571-8
View details for Web of Science ID 000184192300015
View details for PubMedID 12853114
Using positional cloning in a canine model of narcolepsy and mouse gene knockouts, genes involved in the pathogenesis of narcolepsy in animals have been identified. Hypocretin/orexin ligand and hypocretin/orexin receptor genes are key to the pathogenesis of narcolepsy in animals. Mutations in hypocretin-related genes are rare in humans, but hypocretin-ligand deficiency is found in many cases. Hypocretins/orexins are novel hypothalamic neuropeptides involved in various hypothalamic mechanisms, such as energy homeostasis and neuroendocrine function. Hypocretin-deficient human narcolepsy appears to be a more complex condition than a simple sleep disorder, and it may serve as an important disease model for studying hypothalamic function in health and disease.
View details for DOI 10.1016/S0006-3223(03)00349-4
View details for Web of Science ID 000184213800001
View details for PubMedID 12873797
The hypocretins (1 and 2) have emerged as key regulators of sleep and wakefulness. We developed a high-throughput enzyme immunoassay (EIA) to measure total brain hypocretin levels from large numbers of mice. Hypocretin levels were not altered by circadian time or age. However, significant differences in one or both hypocretin peptides were observed between different mouse strains. We studied hypocretin levels in knockout and transgenic mouse models with obesity, circadian gene mutations or monoaminergic defects. Compared to controls, only histamine receptor knockouts had lower hypocretin levels. This was most pronounced in H1 receptor knockouts suggesting the existence of a positive feedback loop between hypocretin and histaminergic neurons.
View details for Web of Science ID 000180769800016
View details for PubMedID 12535700
Delineating the basic mechanisms that regulate sleep will likely result in the development of better treatments for sleep disorders. The hypothalamus is now recognized as a key center for sleep regulation, with hypothalamic neurotransmitter systems providing the framework for therapeutic advances. An increased awareness of the close interaction between sleep and homeostatic systems is also emerging. Progress has occurred in the understanding of narcolepsy--molecular techniques have identified the lateral hypothalamic hypocretin (orexin) neuropeptide system as key to the disorder. Other sleep disorders are now being tackled in the same way and are likely to yield to efforts combining basic and clinical research. Here we highlight the role of the hypothalamus in sleep physiology and discuss neurotransmitter systems, such as adenosine, dopamine, GABA, histamine and hypocretin, that may have therapeutic applications for sleep disorders.
View details for DOI 10.1038/nn944
View details for Web of Science ID 000179041300017
View details for PubMedID 12403989
Narcolepsy, a neurological disorder affecting 1 in 2000 individuals, is associated with HLA-DQB1*0602 and low cerebrospinal fluid (CSF) hypocretin (orexin) levels.To delineate the spectrum of the hypocretin deficiency syndrome and to establish CSF hypocretin-1 measurements as a diagnostic tool for narcolepsy.Diagnosis, HLA-DQ, clinical data, the multiple sleep latency test (MSLT), and CSF hypocretin-1 were studied in a case series of patients with sleep disorders from 1999 to 2002. Signal detection analysis was used to determine the CSF hypocretin-1 levels best predictive for International Classification of Sleep Disorders (ICSD)-defined narcolepsy (blinded criterion standard). Clinical and demographic features were compared in narcoleptic subjects with and without low CSF hypocretin-1 levels.Sleep disorder and neurology clinics in the United States and Europe, with biological testing performed at Stanford University, Stanford, Calif.There were 274 patients with narcolepsy; hypersomnia; obstructive sleep apnea; restless legs syndrome; insomnia; and atypical hypersomnia cases such as familial cases, narcolepsy without cataplexy or without HLA-DQB1*0602, recurrent hypersomnias, and symptomatic cases (eg, Parkinson disease, depression, Prader-Willi syndrome, Niemann-Pick disease type C). The subject group also included 296 controls (healthy and with neurological disorders).Venopuncture for HLA typing, lumbar puncture for CSF analysis, primary diagnosis using the International Classification of Sleep Disorders, Stanford Sleep Inventory for evaluation of narcolepsy, and sleep recording studies.Diagnostic threshold for CSF hypocretin-1, HLA-DQB1*0602 positivity, and clinical and polysomnographic features.HLA-DQB1*0602 frequency was increased in narcolepsy with typical cataplexy (93% vs 17% in controls), narcolepsy without cataplexy (56%), and in essential hypersomnia (52%). Hypocretin-1 levels below 110 pg/mL were diagnostic for narcolepsy. Values above 200 pg/mL were considered normal. Most subjects with low levels were HLA-DQB1*0602-positive narcolepsy-cataplexy patients. These patients did not always have abnormal MSLT. Rare subjects without cataplexy, DQB1*0602, and/or with secondary narcolepsy had low levels. Ten subjects with hypersomnia had intermediate levels, 7 with narcolepsy (often HLA negative, of secondary nature, and/or with atypical cataplexy or no cataplexy), and 1 with periodic hypersomnia. Healthy controls and subjects with other sleep disorders all had normal levels. Neurological subjects had generally normal levels (n = 194). Intermediate (n = 30) and low (n = 3) levels were observed in various acute neuropathologic conditions.Narcolepsy-cataplexy with hypocretin deficiency is a genuine disease entity. Measuring CSF hypocretin-1 is a definitive diagnostic test, provided that it is interpreted within the clinical context. It may be most useful in cases with cataplexy and when the MSLT is difficult to interpret (ie, in subjects already treated with psychoactive drugs or with other concurrent sleep disorders).
View details for Web of Science ID 000178560100005
View details for PubMedID 12374492
View details for PubMedID 14592205
In vitro functional analyses of hypocretin/orexin receptor systems were performed using [(125)I]hypocretin radioreceptor and hypocretin-stimulated [(35)S]GTP gamma S binding assay in cell lines expressing human or canine (wild-type and narcoleptic-mutation) hypocretin receptor 2 (Hcrtr 2). Hypocretin-2 stimulated [(35)S]GTP gamma S binding in human and canine Hcrtr 2 expressing cell lines, while cell lines expressing the mutated canine Hcrtr 2 did not exhibit specific binding for [(125)I]hypocretin or hypocretin-stimulated [(35)S]GTP gamma S. In rat brain homogenates, regional specific hypocretin-stimulated [(35)S]GTP gamma S binding was also observed. Hypocretin-stimulated [(35)S]GTP gamma S binding, may thus be a useful functional assay for hypocretin receptors in both cell lines and brain tissue homogenates.
View details for Web of Science ID 000176364700017
View details for PubMedID 12056812
Hypocretin deficiency is involved in most cases of human narcolepsy. Although cataplexy is pathognomonic of narcolepsy, mechanisms of induction of cataplexy are largely unknown. Patterns of occurrence of cataplectic attacks (i.e. onset location, laterality, and propagation of attacks) in hypocretin receptor 2-mutated narcoleptic Dobermans were characterized in order to understand the basic mechanism of this abnormal sleep-related atonia. Most cataplexy attacks were bilateral (98%) and were initiated in the hind legs (80%). Progression of attacks was also seen (49%) and atonia during propagation was most often bilateral (94%). Involvement of abnormal inactivation of bilateral pathways to the spinal motoneurones due to a deficiency in hypocretin neurotransmission is suggested in the occurrence of cataplexy.
View details for Web of Science ID 000176033900033
View details for PubMedID 12047593
Hypocretins/orexins are newly identified peptides of hypothalamic origin. Hypocretin deficiency is involved in the sleep disorder narcolepsy, suggesting the importance of hypocretin neurotransmission for the regulation of sleep. Hypocretin is known to excite midbrain dopaminergic neurons and to induce hyperactivity and stereotypy in animals. Altered hypocretin neurotransmission might therefore be involved in schizophrenia, since an involvement of dopaminergic mechanisms and an association with sleep disturbance are well demonstrated in patients with schizophrenia. Hypocretin is also known to affect the hypothalamic-pituitary-adrenal axis by stimulating the release of corticotropin releasing hormone (CRH). In the current study, we measured CSF hypocretin levels in 12 controls and 13 patients with chronic schizophrenia associated with moderate sleep disturbance, such as longer sleep onset latency, decreased total sleep time and decreased sleep efficacy. No difference in CSF hypocretin levels between schizophrenia and control subjects was found. CSF hypocretin levels were positively correlated with CSF CRH levels in the patient, control and combined subject populations, but the correlation did not reach statistical significance in any population. The hypocretin levels in schizophrenic patients were, however, positively and significantly correlated with sleep latency, one of the most consistent sleep abnormalities seen in schizophrenia. This correlation was not significant in controls, and no other significant correlation between CSF hypocretin levels and any measure of sleep architecture in either patients or controls was observed. Further studies of whether CNS hypocretin neurotransmission is involved in sleep and neuroendocrine abnormalities seen in patients with schizophrenia and other psychiatric conditions are warranted.
View details for Web of Science ID 000176095700001
View details for PubMedID 12007588
To examine the specificity of low CSF hypocretin-1 levels in narcolepsy and explore the potential role of hypocretins in other neurologic disorders.A method to measure hypocretin-1 in 100 microL of crude CSF sample was established and validated. CSF hypocretin-1 was measured in 42 narcolepsy patients (ages 16-70 years), 48 healthy controls (ages 22-77 years,) and 235 patients with various other neurologic conditions (ages 0-85 years).As previously reported, CSF hypocretin-1 levels were undetectably low (<100 pg/mL) in 37 of 42 narcolepsy subjects. Hypocretin-1 levels were detectable in all controls (224-653 pg/mL) and all neurologic patients (117-720 pg/mL), with the exception of three patients with Guillain-Barré syndrome (GBS). Hypocretin-1 was within the control range in most neurologic patients tested, including patients with AD, PD, and MS. Low but detectable levels (100-194 pg/mL) were found in a subset of patients with acute lymphocytic leukemia, intracranial tumors, craniocerebral trauma, CNS infections, and GBS.Undetectable CSF hypocretin-1 levels are highly specific to narcolepsy and rare cases of GBS. Measuring hypocretin-1 levels in the CSF of patients suspected of narcolepsy is a useful diagnostic procedure. Low hypocretin levels are also observed in a large range of neurologic conditions, most strikingly in subjects with head trauma. These alterations may reflect focal lesions in the hypothalamus, destruction of the blood brain barrier, or transient or chronic hypofunction of the hypothalamus. Future research in this area is needed to establish functional significance.
View details for Web of Science ID 000172891500018
View details for PubMedID 11756606
A growing amount of evidence suggests that a deficiency in hypocretin/orexin neurotransmission is critically involved in animal and human forms of narcolepsy. Since hypocretin-containing neurons innervate and excite histaminergic tuberomammillary neurons, altered histaminergic neurotransmission may also be involved in narcolepsy. We found a significant decrease in histamine content in the cortex and thalamus, two structures important for histamine-mediated cortical arousal, in Hcrtr-2 mutated narcoleptic Dobermans. In contrast, dopamine and norepinephrine contents in these structures were elevated in narcoleptic animals, a finding consistent with our hypothesis of altered catecholaminergic transmission in these animals. Considering the fact that histamine promotes wakefulness, decreases in histaminergic neurotransmission may also account for the sleep abnormalities in hypocretin-deficient narcolepsy.
View details for Web of Science ID 000172056000004
View details for PubMedID 11682143
Hypocretins/orexins are neuropeptides implicated in sleep regulation and the sleep disorder narcolepsy. In order to examine how hypocretin activity fluctuates across 24 h with respect to the sleep-wake cycle, we measured changes in extracellular hypocretin-1 levels in the lateral hypothalamus and medial thalamus of freely moving rats with simultaneous sleep recordings. Hypocretin levels exhibited a robust diurnal fluctuation; levels slowly increased during the dark period (active phase), and decreased during the light period (rest phase). Levels were not correlated with the amount of wake or sleep in each period. Although an acute 4-h light-shift did not alter hypocretin levels, 6-h sleep deprivation significantly increased hypocretin release during the forced-wake period. Hypocretin activity is, thus, likely to build up during wakefulness and decline with the occurrence of sleep. These findings, together with the fact that a difficulty in maintaining wakefulness during the daytime is one of the primary symptoms of hypocretin-deficient narcolepsy, suggest that hypocretin activity may be critical in opposing sleep propensity during periods of prolonged wakefulness.
View details for Web of Science ID 000171795700004
View details for PubMedID 11683899
Hypocretins (orexins) are hypothalamic neuropeptides involved in sleep and energy homeostasis. Hypocretin mutations produce narcolepsy in animal models. In humans, narcolepsy is rarely due to hypocretin mutations, but this system is deficient in the cerebrospinal fluid (CSF) and brain of a small number of patients. A recent study also indicates increased body mass index (BMI) in narcolepsy. The sensitivity of low CSF hypocretin was examined in 38 successive narcolepsy-cataplexy cases [36 human leukocyte antigen (HLA)-DQB1*0602-positive] and 34 matched controls (15 controls and 19 neurological patients). BMI and CSF leptin levels were also measured. Hypocretin-1 was measurable (169 to 376 pg/ml) in all controls. Levels were unaffected by freezing/thawing or prolonged storage and did not display any concentration gradient. Hypocretin-1 was dramatically decreased (<100 pg/ml) in 32 of 38 patients (all HLA-positive). Four patients had normal levels (2 HLA-negative). Two HLA-positive patients had high levels (609 and 637 pg/ml). CSF leptin and adjusted BMI were significantly higher in patients versus controls. We conclude that the hypocretin ligand is deficient in most cases of human narcolepsy, providing possible diagnostic applications. Increased BMI and leptin indicate altered energy homeostasis. Sleep and energy metabolism are likely to be functionally connected through the hypocretin system.
View details for Web of Science ID 000170803200014
View details for PubMedID 11558795
Familial and sporadic forms of narcolepsy exist in both humans and canines. Mutations in the hypocretin receptor 2 gene (Hcrtr 2) cause canine familial narcolepsy. In humans, mutations in hypocretin-related genes are rare, but cerebrospinal fluid (CSF) hypocretin-1 is undetectable in most sporadic cases. Using the canine model, we investigated ( 1 ) whether hypocretin deficiency is involved in sporadic cases and ( 2 ) whether alterations in hypocretin neurons or ligand levels also contribute to the phenotype in Hcrtr 2 mutants. We found that hypocretins were undetectable in the brains of three of three and the CSF of two of two sporadic narcoleptic dogs tested. In contrast, hypocretin levels were not altered in brains and CSF of genetically narcoleptic Dobermans, and hypocretin-containing neurons were of normal appearance. Therefore, multiple hypocretin-related etiologies are likely to be involved in canine narcolepsy. The presence of hypocretin peptides in Hcrtr 2-mutated animals suggests that neurotransmission through Hcrtr 1 may be intact, arguing for a preferential importance of Hcrtr 2-mediated function in narcolepsy.
View details for Web of Science ID 000169459000014
View details for PubMedID 11442359
Hypocretin-1 is consistently detectable in the CSF of healthy human subjects, but is absent in narcoleptics. However, functional roles of CSF hypocretin are largely unknown. We examined fluctuation of CSF hypocretin-1 across 24 h and in response to food restriction in rats. Hypocretin-1 levels were high during the dark period when animals were active, but decreased by 40% toward the end of the light (rest) period. After 72 h food deprivation hypocretin-1 levels during the rest phase increased to concentrations similar to those seen during the baseline active phase; however, no increase in response to food deprivation was observed during the active phase. These results indicate an important link between circadian control of sleep and energy homeostasis via the hypocretin system.
View details for Web of Science ID 000167905600027
View details for PubMedID 11303775
The role of dopamine in sleep regulation and in mediating the effects of wake-promoting therapeutics is controversial. In this study, polygraphic recordings and caudate microdialysate dopamine measurements in narcoleptic dogs revealed that the wake-promoting antinarcoleptic compounds modafinil and amphetamine increase extracellular dopamine in a hypocretin receptor 2-independent manner. In mice, deletion of the dopamine transporter (DAT) gene reduced non-rapid eye movement sleep time and increased wakefulness consolidation independently from locomotor effects. DAT knock-out mice were also unresponsive to the normally robust wake-promoting action of modafinil, methamphetamine, and the selective DAT blocker GBR12909 but were hypersensitive to the wake-promoting effects of caffeine. Thus, dopamine transporters play an important role in sleep regulation and are necessary for the specific wake-promoting action of amphetamines and modafinil.
View details for Web of Science ID 000167129700040
View details for PubMedID 11222668
Narcolepsy is a chronic sleep disorder marked by excessive daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic hallucinations. Since the discovery of sleep onset REM periods (SOREMPs) in narcoleptic patients, narcolepsy has often been regarded as a disorder of REM sleep generation: REM sleep intrudes in active wake or at sleep onset, resulting in cataplexy, sleep paralysis, or hypnagogic hallucinations. However, this hypothesis has not been experimentally verified. In the current study, we characterized the sleep abnormalities of genetically narcoleptic-cataplectic Dobermans, a naturally occurring animal model of narcolepsy, in order to verify this concept. Multiple sleep latency tests during the daytime revealed that narcoleptic Dobermans exhibit a shorter sleep latency and a higher frequency of SOREMPs, compared to control Dobermans. The total amount of time spent in wake and sleep during the daytime is not altered in narcoleptic dogs, but their wake and sleep patterns are fragmented, and state transitions into and from wake and other sleep stages are altered. A clear 30 min REM sleep cyclicity exists in both narcoleptic and control dogs, suggesting that generation of the ultradian rhythm of REM sleep is not altered in narcoleptics. In contrast, cataplexy displays no cyclicity and can be elicited in narcoleptic animals anytime with emotional stimulation and displays no cyclicity. Stimulation of a cholinoceptive site in the basal forebrain induces a long-lasting attack of cataplexy in narcoleptic dogs; however, bursts of rapid eye movements during this state still occur with a 30 min cyclicity. Sites and mechanisms for triggering cataplexy may therefore be different from those for REM sleep. Cataplexy and a dysfunction in the maintenance of vigilance states, but not abnormal REM sleep generation, may therefore be central to narcolepsy.
View details for Web of Science ID 000166120200013
View details for PubMedID 11164570
Cataplexy, an abnormal manifestation of REM sleep atonia, is currently treated with antidepressants. These medications also reduce physiological REM sleep and induce nocturnal sleep disturbances. Because a recent work on canine narcolepsy suggests that the mechanisms for triggering cataplexy are different from those for REM sleep, we hypothesized that compounds which act specifically on cataplexy, but not on REM sleep, could be developed. Canine studies also suggest that the dopamine D2/D3 receptor mechanism is specifically involved in the regulation of cataplexy, but little evidence suggests that this mechanism is important for REM sleep regulation. We therefore assessed the effects of sulpiride, a commonly used D2/D3 antagonist, on cataplexy and sleep in narcoleptic canines to explore the possible clinical application of D2/D3 antagonists for the treatment of human narcolepsy. Both acute and chronic oral administration of sulpiride (300 mg/dog, 600 mg/dog) significantly reduced cataplexy without noticeable side effects. Interestingly, the anticataplectic dose of sulpiride did not significantly reduce the amount of REM sleep. Sulpiride (and other D2/D3 antagonists) may therefore be an attractive new therapeutic indication in human narcolepsy.
View details for Web of Science ID 000089867500005
View details for PubMedID 11027918
We explored the role of hypocretins in human narcolepsy through histopathology of six narcolepsy brains and mutation screening of Hcrt, Hcrtr1 and Hcrtr2 in 74 patients of various human leukocyte antigen and family history status. One Hcrt mutation, impairing peptide trafficking and processing, was found in a single case with early onset narcolepsy. In situ hybridization of the perifornical area and peptide radioimmunoassays indicated global loss of hypocretins, without gliosis or signs of inflammation in all human cases examined. Although hypocretin loci do not contribute significantly to genetic predisposition, most cases of human narcolepsy are associated with a deficient hypocretin system.
View details for Web of Science ID 000089190500030
View details for PubMedID 10973318
The effects on cataplexy and daytime sleep of acute and chronic oral administration of CG-3703, a potent TRH analog were assessed in canine narcolepsy. CG-3703 was found to be orally active and to reduce cataplexy (0.25 to 16 mg/kg) and sleep (8 and 16 mg/kg) in a dose-dependent manner. Two-week oral administration of CG-3703 (16 mg/kg) significantly reduced cataplexy and daytime sleep. The anticataplectic effects of CG-3703 were not associated with changes in general behavior, heart rate, blood pressure, rectal temperature, blood chemistry and thyroid function. Although drug tolerance for the effects on cataplexy and sleep were observed during the second week of chronic drug administration, therapeutic efficacy on cataplexy was improved with individual dose adjustment (final dose range: 16 to 28 mg/kg, p.o.). These results suggest that TRH analogs could be a promising new form of treatment for human narcolepsy.
View details for Web of Science ID 000087772700004
View details for PubMedID 10869884
To determine the mode of inheritance of von Willebrand's disease (vWD) and perform linkage analysis between vWD and coat color or narcolepsy in a colony of Doberman Pinschers.159 Doberman Pinschers.von Willebrand factor antigen (vWF:Ag) concentration was measured by use of ELISA, and results were used to classify dogs as having low (< 20%), intermediate (20 to 65%), or high (> 65%) vWF:Ag concentration, compared with results of analysis of standard pooled plasma. Buccal bleeding time was measured, and mode of inheritance of vWD was assessed by pedigree analysis.von Willebrand's disease was transmitted as a single autosomal gene defect. Results suggested that 27.04% of dogs were homozygous for vWD, 62.26% were heterozygous, and 10.69% did not have the defect. Most homozygous and some heterozygous dogs had prolonged bleeding times. Dogs with diluted coat colors (blue and fawn) were significantly overrepresented in the homozygous group, compared with black and red dogs, but a significant link between vWD and coat color was not detected.von Willebrand's disease is transmitted as an autosomal dominant trait with variable penetrance; most dogs in this colony (89.3%) were carriers of vWD. Homozygosity for vWD is not likely to be lethal. Some heterozygous dogs have prolonged bleeding times. An association between diluted coat colors and vWD may exist.
View details for Web of Science ID 000085055600002
View details for PubMedID 10685679
Narcolepsy is a disabling sleep disorder characterized by excessive daytime somnolence (EDS), cataplexy and REM sleep-related abnormalities. It is a frequently-occurring but under-diagnosed condition that affects 0.02 to 0.18% of the general population in various countries. Although most cases occur sporadically, familial clustering may be observed; the risk of a first-degree relative of a narcoleptic developing narcolepsy is 10-40 times higher than in the general population. The disorder is tightly associated with the specific human leukocyte antigen (HLA) allele, DQB1*0602 [most often in combination with HLA-DR2 (DRB1*15)]. Genetic transmission is, however, likely to be polygenic in most cases, and genetic factors other than HLA-DQ are also likely to be implicated. In addition, environmental factors are involved in disease predisposition; most monozygotic twins pairs reported in the literature are discordant for narcolepsy. Narcolepsy was reported to exist in canines in the early 1970s. Both sporadic and familial cases are also observed in this animal species. A highly-penetrant single autosomal recessive gene, canarc-1, is involved in the transmission of narcolepsy in Doberman pinschers and Labrador retrievers. Positional cloning of this gene is in progress, and a human homologue of this gene, or a gene with a functional relationship to canarc-1, might be involved in some human cases. Human narcolepsy is currently treated with central nervous system (CNS) stimulants for EDS and antidepressants for cataplexy and abnormal REM sleep. These treatments are purely symptomatic and induce numerous side effects. These compounds disturb nocturnal sleep in many patients, and tolerance may develop as a result of continuous treatment. The canine model is an invaluable resource for studying the pharmacological and physiological control of EDS and cataplexy. Experiments using canine narcolepsy have demonstrated that increased cholinergic and decreased monoaminergic transmission are likely to be at the basis of the pathophysiology of the disorder. Pharmacological studies have shown that blockade of norepinephrine uptake mediates the anticataplectic effect of currently prescribed antidepressants, while blockade of dopamine uptake and/or stimulation of dopamine release mediates the awake-promoting effect of CNS stimulants. Studies in canine narcolepsy also suggest that mechanisms and brain sites for triggering cataplexy are not identical to those regulating REM sleep. It may thus be possible to develop new pharmacological compounds that specifically target abnormal symptoms in narcolepsy, but do not disturb physiological sleep/wake cycles. (See also postscript remarks).
View details for PubMedID 12531161
Using a canine model of narcolepsy and selective DA and NE uptake inhibitors, we have recently shown that DA uptake inhibition promotes wakefulness, while NE uptake inhibition inhibits rapid eye movement sleep and cataplexy. In order to further delineate the respective roles of the dopaminergic and noradrenergic systems in the pharmacological control of symptoms of narcolepsy, we compared the potency of amphetamine isomers (D- and L-amphetamines) and a derivative (L-methamphetamine) on wakefulness and cataplexy. Their respective effects on these narcolepsy symptoms were then compared with their in vivo effects on extracellular DA levels in the caudate and NE levels in the frontal cortex during local drug perfusion in narcoleptic dogs. Polygraphic recordings demonstrated that D-amphetamine was about twice as potent as L-amphetamine, and was six times more potent than L-methamphetamine in increasing wakefulness and reducing slow-wave sleep. D-Amphetamine and L-amphetamine were equipotent in reducing rapid eye movement sleep and cataplexy, and L-methamphetamine was about half as potent as L- and D-amphetamines. D-Amphetamine was found to be more potent in increasing DA efflux than L-amphetamine, and L-methamphetamine was found to have little effect on DA efflux; there was no significant difference in the potencies of the three derivatives on NE efflux. The potencies of these amphetamines on wakefulness correlated well with DA, but not NE, efflux in the brain of narcoleptic dogs during local drug perfusion. Our current results further exemplify the importance of the DA system for the pharmacological control of electroencephalogram arousal and suggest that increased DA transmission mediates the wake-promoting effects of amphetamine-like stimulants.
View details for Web of Science ID 000089250800007
View details for PubMedID 10974428
We have recently demonstrated that local perfusion of dopaminergic D2/D3 agonists into the ventral tegmental area (VTA) significantly aggravates cataplexy and increases sleep in narcoleptic Dobermans. We further assessed the roles of the mesostriatal dopaminergic system and found that local perfusion of quinpirole and 7-OH-DPAT into the substantia nigra (SN) significantly aggravated cataplexy, while perfusion of a D2/D3 antagonist significantly reduced cataplexy. Neither a D1 agonist nor a D1 antagonist modified cataplexy. SN perfusion of quinpirole did not significantly modify sleep, while VTA perfusion significantly increased the drowsy state. Although autoregulation of the VTA and SN dopaminergic neurons are involved in the regulation of cataplexy, both structures have distinct roles for the regulation of sleep.
View details for Web of Science ID 000083934000001
View details for PubMedID 10619672
Insomnia and excessive daytime sleepiness (EDS) are frequently observed conditions in the general public. A national survey in the USA in 1979 indicated that 35% of American adults experience insomnia in the course of a year. The prevalence of EDS varies depending on the survey (0.3 to 13.3%), but a recent study stated that 2.4% of individuals reported that they continually fell asleep at work. These problems are often long term and negatively affect the individuals' quality of life. People with these sleep problems often have difficulties maintaining high levels of productivity at work or pursuing their daily activities; individuals with insomnia lack the feeling of being rested or refreshed in the morning and EDS is unavoidable in most cases. Behavioural therapy has been shown to be effective for many people affected with insomnia and EDS. However, pharmacological treatments using hypnosedatives and central nervous system (CNS) stimulants are usually necessary, and effective, for those with more severe cases. These compounds have thus been widely prescribed in clinical practice (e.g., 2.6% of all adults surveyed used medically prescribed hypnosedatives and 4.5% used over-the-counter drugs to promote sleep). The onset and duration of action of these hypnosedatives and CNS stimulant drugs are important factors to be considered when prescribing these compounds. These factors primarily depend on physicochemical properties (lipid solubility and protein binding), as well as the pharmacokinetic profile (absorption, distribution, elimination and clearance) of the compounds. Significant differences in profile exist amongst hypnosedatives and CNS stimulants, and these differences may account for the observed variations in clinical action and adverse effects during and after treatment. In this review, we will introduce recently obtained knowledge of the pharmacokinetics of hypnosedatives and CNS stimulants and their applications for patients affected with insomnia and EDS.
View details for Web of Science ID 000083428700003
View details for PubMedID 10554047
We have recently demonstrated that local perfusion of dopaminergic D2/D3 agonists into the ventral tegmental area (VTA) significantly aggravates cataplexy and increases sleep in narcoleptic Dobermans. We further assessed the roles of the mesostriatal dopaminergic system and found that local perfusion of quinpirole and 7-OH-DPAT into the substantia nigra (SN) significantly aggravated cataplexy, while perfusion of a D2/D3 antagonist significantly reduced cataplexy. Neither a D1 agonist nor a D1 antagonist modified cataplexy. SN perfusion of quinpirole did not significantly modify sleep, while VTA perfusion significantly increased the drowsy state. Although autoregulation of the VTA and SN dopaminergic neurons are involved in the regulation of cataplexy, both structures have distinct roles for the regulation of sleep.
View details for Web of Science ID 000082865500046
View details for PubMedID 10549832
Narcolepsy is a disabling sleep disorder affecting humans and animals. It is characterized by daytime sleepiness, cataplexy, and striking transitions from wakefulness into rapid eye movement (REM) sleep. In this study, we used positional cloning to identify an autosomal recessive mutation responsible for this sleep disorder in a well-established canine model. We have determined that canine narcolepsy is caused by disruption of the hypocretin (orexin) receptor 2 gene (Hcrtr2). This result identifies hypocretins as major sleep-modulating neurotransmitters and opens novel potential therapeutic approaches for narcoleptic patients.
View details for Web of Science ID 000081950300011
View details for PubMedID 10458611
Cholinergic stimulation in the basal forebrain (BF) triggers cataplexy in canine narcolepsy. Extracellular single unit recordings in the BF were carried out in freely moving narcoleptic dogs to study the neuronal mechanisms mediating cataplexy induction in the BF. Among the 64 recorded neurons, 12 were wake-active, three were slow wave sleep (SWS)-active, 17 were wake-/REM-active, 11 were REM sleep-active, three were cataplexy-active, and the other 18 were state-independent. Systemic administration of physostigmine, a cholinesterase inhibitor, induces status cataplecticus, decreases SWS and increases acetylcholine levels in the BF. Firing of most of the state-dependent neurons in the BF was significantly modified by physostigmine. Some of these neurons may thus mediate sleep stage changes or the effect on cataplexy observed after cholinergic stimulation in the BF.
View details for Web of Science ID 000077493400021
View details for PubMedID 9858375
Forty-two genetically narcoleptic Doberman puppies [20 pure narcoleptic (N) puppies (from four narcoleptic x narcoleptic crosses) and 22 backcross narcoleptic (BN) puppies (from six narcoleptic x heterozygous crosses)] were systematically observed during the developmental period (4-24 weeks) to assess the age at onset and severity of cataplexy, a pathological manifestation of REM sleep atonia seen in narcolepsy. The mean age of onset of cataplexy was 9.69 +/- 1.15 weeks, with a median age of 7 weeks. The severity of cataplexy increased with age and reached a plateau at around 16-24 weeks. The effects of cross type (N vs BN) and sex on the development of cataplexy were analyzed. There was no difference in severity between N and BN puppies (P = 0.51). However, females had more severe cataplexy than males (P = 0.01), and this trend was preserved in five of the six litters that had both male and female puppies. These results suggest that the pathophysiological process in genetic canine narcolepsy emerges during the early developmental period and that it may involve a differential development in males and females. Furthermore, our results revealed that cataplexy onset corresponds to the emergence of adult-like REM sleep and to previously reported neuroanatomical and neurochemical abnormalities in canine narcolepsy.
View details for Web of Science ID 000075698200014
View details for PubMedID 9710528
Sleep abnormalities have been consistently observed in patients with schizophrenia. Elevated levels of corticotropin releasing factor (CRF) and prostaglandins (PGs) in the cerebrospinal fluid (CSF) of patients with schizophrenia have been reported, and these neurochemical substances, known to modulate sleep in experimental animals, may play a role in these sleep abnormalities. In this study, we measured PGD2, PGE2, PGF2alpha and CRF levels in the CSF of 14 unmedicated schizophrenic patients and 14 age- and sex-matched control subjects. Polysomnographic recordings were also carried out for each subject. As expected, the sleep of the schizophrenic subjects significantly differed from that of the controls; schizophrenic subjects had a longer sleep onset latency, slept less, spent fewer minutes in stage 2 sleep and had a lower sleep efficiency. We could not, however, detect any differences in CSF CRF and PG levels between normal and schizophrenic subjects, nor could we find any correlation between CSF variables and sleep parameters in the schizophrenic subjects and the non-psychiatric controls. These results do not favor the hypothesis of a role for CRF or PGs in the pathophysiology of sleep disturbances in schizophrenia.
View details for Web of Science ID 000074238900003
View details for PubMedID 9657418
Basal forebrain (BF) cholinergic regulation of cataplexy was investigated in narcoleptic canines. Specific cholinergic agonists and antagonists, and excitatory or inhibitory amino acid neurotransmitter receptor agonists, were perfused through microdialysis probes implanted bilaterally in the BF of narcoleptic canines. Cataplexy was monitored using the food-elicited cataplexy test (FECT) and recordings of electroencephalogram, electrooculogram, and electromyogram. In narcoleptic canines, carbachol and oxotremorine (10(-5)-10(-3) M), but not McN-A-343 or nicotine (10(-4)-10(-3) M), produced a dose-dependent increase in cataplexy. In addition, N-methyl-d-aspartate (10(-4)-10(-3) M) and kainic acid (10(-5)-10(-4) M) did not have any effects, while muscimol (10(-3) M) produced a weak (P < 0.10) increase in cataplexy. In control canines, carbachol (10(-5)-10(-3) M), but not oxotremorine (10(-4)-10(-3) M), produced muscle atonia after the highest concentration in one of three animals. Carbachol (10(-3) M)-induced cataplexy in narcoleptic canines was blocked by equimolar perfusion with the muscarinic antagonists atropine, gallamine, and 4-DAMP but not pirenzepine. These findings indicate that carbachol-stimulated cataplexy in the BF of narcoleptic canines is mediated by M2, and perhaps M3, muscarinic receptors. The release of acetylcholine in the BF was also examined during FECT and non-FECT behavioral stimulation in narcoleptic and control canines. A significant increase in acetylcholine release was found in both narcoleptic and control BF during FECT stimulation. In contrast, simple motor activity and feeding, approximating that which occurs during an FECT, did not affect acetylcholine release in the BF of narcoleptic canines. These findings indicate that BF acetylcholine release is enhanced during learned emotion/reward associated behaviors in canines.
View details for Web of Science ID 000073593600008
View details for PubMedID 9582257
Narcolepsy is a disabling sleep disorder of unknown aetiology. In humans, the disease is mostly sporadic, with a few familial cases having been reported. In 1973 a sporadic case of narcolepsy was reported in a poodle, and in 1975 familial cases of narcolepsy occurred in dobermanns. As with human narcoleptics, these narcoleptic dogs exhibited excessive daytime sleepiness and cataplexy. A colony of narcoleptic dogs was established at Stanford University in 1976 to study the pathophysiology of the disease. Between 1976 and 1995, a total of 669 animals of various breeds were born, of which 487 survived. Dobermanns accounted for 78 per cent of the total. The narcolepsy genotype in dobermanns had no significant influence on puppy mortality rate (numbers of stillborn and survival rate). The sex, maternal parity or the age of the sire or dam had no significant effect. The percentage of stillborn puppies increased from 6.1 per cent in outbred litters to 15.4 per cent in inbred litters (P = 0.10). Birth season also had a significant effect, and the highest survival rate (P = 0.02), and the lowest percentage of stillborn puppies (P = 0.09) occurred between April and June.
View details for Web of Science ID 000071662300006
View details for PubMedID 9481825
Amphetamine-like stimulants are commonly used to treat sleepiness in narcolepsy. These compounds have little effect on rapid eye movement (REM) sleep-related symptoms such as cataplexy, and antidepressants (monoamine uptake inhibitors) are usually required to treat these symptoms. Although amphetamine-like stimulants and antidepressants enhance monoaminergic transmission, these compounds are non-selective for each monoamine, and the exact mechanisms mediating how these compounds induce wakefulness and modulate REM sleep are not known. In order to evaluate the relative importance of dopaminergic and noradrenergic transmission in the mediation of these effects, five dopamine (DA) uptake inhibitors (mazindol, GBR-12909, bupropion, nomifensine and amineptine), two norepinephrine (NE) uptake inhibitors (nisoxetine and desipramine), d-amphetamine, and modafinil, a non-amphetamine stimulant, were tested in control and narcoleptic canines. All stimulants and dopaminergic uptake inhibitors were found to dose-dependently increase wakefulness in control and narcoleptic animals. The in vivo potencies of DA uptake inhibitors and modafinil on wake significantly correlated with their in vitro affinities to the DA and not the NE transporter. DA uptake inhibitors also moderately reduced REM sleep, but this effect was most likely secondary to slow wave sleep (SWS) suppression, since selective DA uptake inhibitors reduced both REM sleep and SWS proportionally. In contrast, selective NE uptake inhibitors had little effect on wakefulness, but potently reduced REM sleep. These results suggest that presynaptic activation of DA transmission is critical for the pharmacological control of wakefulness, while that of the NE system is critical for REM sleep regulation. Our results also suggest that presynaptic activation of DA transmission is a key pharmacological property mediating the wake-promoting effects of currently available CNS stimulants.
View details for PubMedID 11382857
Experimental evidence in canine narcolepsy suggests that central cholinergic systems are critically involved in the regulation of cataplexy, an abnormal manifestation of REM sleep atonia. In the current study, we found that intracerebroventricular perfusion of methyl-B12, (10(-5)-10(-2) M), significantly aggravated cataplexy and enhanced REM sleep in narcoleptic dogs. Choline, a direct precursor of acetylcholine, was also found to aggravate cataplexy, while cyano-B12, a vitamin B12 analog without methyl donating abilities, had no effect on cataplexy. Since both methyl-B12 and choline are reported to enhance acetylcholine synthesis, enhancement of the biosynthesis of acetylcholine may be involved in the effects observed in canine narcolepsy. Our results suggest that central administration of methyl-B12 has the potential to modulate both normal and pathological REM sleep.
View details for Web of Science ID 000071221500006
View details for PubMedID 9462456
The therapeutic potential of thyrotropin-releasing hormone (TRH) and TRH analogs in narcolepsy, a sleep disorder characterized by abnormal rapid eye movement (REM) sleep and daytime sleepiness, was examined using the canine model. The effects of TRH and the biologically stable TRH analogs CG3703, CG3509, and TA0910 on daytime sleep and cataplexy, a symptom of abnormal REM sleep, were assessed using polysomnographic recordings and the food elicited cataplexy test (FECT), respectively. CG3703 (100 and 400 microg/kg, i.v.) and TA0910 (100 and 400 microg/kg, i.v.) significantly increased wakefulness and decreased sleep in narcoleptic canines, whereas TRH (400 and 1600 microg/kg, i.v.) had no significant effect. TRH (25-1600 microg/kg, i.v.) and all three TRH analogs, CG3703 (6. 25-400 microg/kg, i.v., and 0.25-16 mg/kg, p.o.), CG3509 (25-1600 microg/kg, i.v.), and TA0910 (25-1600 microg/kg, i.v.), significantly reduced cataplexy in canine narcolepsy. These compounds did not produce any significant side effects during behavioral assays, nor did they alter free T3 and T4 levels in serum even when used at doses that completely suppressed cataplexy. Although more work is needed to establish the mode of action of TRH analogs on alertness and REM sleep-related symptoms, our results suggest a possible therapeutic application for TRH analogs in human sleep disorders.
View details for Web of Science ID A1997XU78100037
View details for PubMedID 9236248
Like human narcoleptics, narcoleptic dogs display cataplexy, fragmented sleep and excessive daytime sleepiness. Cataplexy in dogs can easily be quantified using a simple behavioural bioassay, the Food Elicited Cataplexy Test. In contrast, daytime sleepiness and fragmented sleep are more difficult to measure, as long-term, labour-intensive polygraphic recordings in surgically-implanted animals are needed. In the current study, 24-h rest/activity patterns in genetically narcoleptic, asymptomatic heterozygous and control Dobermans were compared using small sized ambulatory activity monitoring devices under 12-h light/dark conditions. Control and heterozygous dogs were found to be more active during the light period than during the dark period, thus demonstrating a clear 24-h rest/activity cycle. In contrast, narcoleptic dogs were relatively inactive during the light period and did not show a clear rest/activity pattern, a result similar to that of human narcoleptics. Considering the fact that narcoleptic dogs show shorter sleep latency and sleep significantly more during the daytime than control dogs, the decrease in activity in narcoleptic dogs during the daytime is most likely a reflection of increased daytime napping in these animals. Ambulatory activity monitoring may be a useful non-invasive method for future pharmacological and development studies in the narcoleptic canine model.
View details for Web of Science ID A1997XL41000007
View details for PubMedID 9377531
Narcolepsy-cataplexy is a disabling neurological disorder that affects 1/2000 individuals. The main clinical features of narcolepsy, excessive daytime sleepiness and symptoms of abnormal REM sleep (cataplexy, sleep paralysis, hypnagogic hallucinations) are currently treated using amphetamine-like compounds or modafinil and antidepressants. Pharmacological research in the area is facilitated greatly by the existence of a canine model of the disorder. The mode of action of these compounds involves presynaptic activation of adrenergic transmission for the anticataplectic effects of antidepressant compounds and presynaptic activation of dopaminergic transmission for the EEG arousal effects of amphetamine-like stimulants. The mode of action of modafmil is still uncertain, and other neurochemical systems may offer interesting avenues for therapeutic development. Pharmacological and physiological studies using the canine model have identified primary neurochemical and neuroanatomical systems that underlie the expression of abnormal REM sleep and excessive sleepiness in narcolepsy. These involve mostly the pontine and basal forebrain cholinergic, the pontine adrenergic and the mesolimbic and mesocortical dopaminergic systems. These studies confirm a continuing need for basic research in both human and canine narcolepsy, and new treatments that act directly at the level of the primary defect in narcolepsy might be forthcoming.
View details for Web of Science ID A1997XC57300002
View details for PubMedID 9185233
Canine narcolepsy is a unique experimental model of a human sleep disorder characterized by excessive daytime sleepiness and cataplexy. There is a consensus recognition of an imbalance between cholinergic and catecholaminergic systems in narcolepsy although the underlying mechanisms remain poorly understood. Possible substrates could be an abnormal organization, numbers and/or ratio of cholinergic to catecholaminergic cells in the brain of narcoleptic dogs. Therefore, we sought to characterize the corresponding neuronal populations in normal and narcoleptic dogs (Doberman Pinscher) by using choline acetyltransferase (ChAT), nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase, tyrosine hydroxylase (TH), and dopamine beta-hydroxylase (DBH). Cholinergic cell groups were found in an area extending from the central to the gigantocellular tegmental field and the periventricular gray corresponding to the pedunculopontine tegmental nucleus (PPT), the laterodorsal tegmental nucleus (LDT), and the parabrachial nucleus. An almost perfect co-localization of ChAT and NADPH-diaphorase was also observed. Catecholaminergic cell groups detected included the ventral tegmental area, the substantia nigra, and the locus coeruleus nucleus (LC). The anatomical distribution of catecholaminergic neurons was unusual in the dog in two important aspects: i) TH- and/or DBH-immunoreactive neurons of the LC were found almost exclusively in the reticular formation and not within the periventricular gray, ii) very few, if any TH-positive neurons were found in the central gray and dorsal raphe. Quantitative analysis did not reveal any significant differences in the organization and the number of cells identified in the LDT, PPT, and LC of normal and narcoleptic dogs. Moreover, the cholinergic to catecholaminergic ratio was found identical in the two groups. In conclusion, the present results do not support the hypothesis that the neurochemical imbalance in narcolepsy could result from abnormal organization, numbers, or ratio of the corresponding neuronal populations.
View details for Web of Science ID A1997WL65800002
View details for PubMedID 9050784
Thalidomide is a sedative hypnotic that was widely used in the 1950s but was withdrawn due to its teratogenic properties. The compound has recently been reintroduced as an immune modulating agent. Thalidomide significantly aggravates canine cataplexy, a pathological manifestation of rapid eye movement (RFM) sleep atonia seen in narcolepsy. This compound also increases REM sleep and slow wave sleep in these animals. In vitro receptor binding and enzyme assays demonstrate that thalidomide does not bind to or enzymatically modulate the neurotransmitter systems reported to be involved in the regulation of cataplexy. Thalidomide may therefore affect cataplexy through its immune modulation properties. Further studies on the mechanisms of action of thalidomide should increase our understanding of the pathophysiology of this disabling disorder.
View details for Web of Science ID A1996VP15900002
View details for PubMedID 8905685
Human narcolepsy is a neurological disorder known to be closely associated with HLA-DR2 and DQB1*0602. Because most autoimmune diseases are HLA-associated, a similar mechanism has been proposed for narcolepsy. However, neither systemic nor CNS evidence of an autoimmune abnormality has ever been reported. In this study, major histocompatibility (MHC) class I and class II expression was studied in the CNS of human and canine narcoleptics using immunohistochemistry and Northern analysis. Results indicated that canine narcolepsy is associated with a significant increase of MHC class II expression by the microglia. Moreover, the highest values were found between 3 and 8 months of age, strikingly concomitant to the development of narcolepsy in the canine model. In humans, class II expression was not found significantly different between control and narcoleptic subjects. This result could be explained by the old age of the subjects (69.86 +/- 5.31 and 68.36 +/- 4.74 years in narcoleptics and controls, respectively), because class II expression is significantly correlated with age in both humans and dogs. For the first time, this study demonstrated that the expression of MHC class II molecules in the CNS is age-dependent and that a consistent increase of their expression by the microglia might be critically involved in the development of narcolepsy.
View details for Web of Science ID A1996UX95500006
View details for PubMedID 8764647
The effects of modafinil and amphetamine on daytime sleep (polysomnographic recordings) and cataplexy (the food-elicited cataplexy test) were compared using the narcoleptic canine model. Results indicate that both modafinil (5 and 10 mg/kg body weight i.v.) and amphetamine (100 and 200 micrograms/kg i.v.) increase wakefulness and reduce slow-wave sleep in control and narcoleptic dogs. In contrast, the results of cataplexy testing demonstrate that amphetamine (2.5-160 micrograms/kg i.v.), but not modafinil (0.125-8.0 mg/kg i.v.) significantly suppresses canine cataplexy. These results suggest that the pharmacological property of modafinil is distinct from amphetamine. Results of polysomnographic recordings also demonstrate that narcoleptic dogs slept significantly more during the daytime than control dogs and required very high doses (10 mg/kg i.v. modafinil; 200 micrograms/kg i.v. amphetamine) of stimulants to reduce their level of sleepiness to that of control dogs. This finding is consistent with the data collected in human narcolepsy and validates the use of this canine model for the screening of stimulant compounds.
View details for Web of Science ID A1995TQ23600001
View details for PubMedID 8746387
Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness and rapid eye movement (REM) sleep-related symptoms, such as cataplexy. The exact pathophysiology underlying the disease is unknown but may involve central cholinergic systems. It is known that the brainstem cholinergic system is activated during REM sleep. Furthermore, REM sleep and REM sleep atonia similar to cataplexy can be triggered in normal and narcoleptic dogs by stimulating cholinergic receptors within the pontine brainstem. The pontine cholinergic system is, therefore, likely to play a role in triggering cataplexy and other REM-related abnormalities seen in narcolepsy. The other cholinergic system that could be involved in the pathophysiology of narcolepsy is located in the basal forebrain (BF). This system sends projections to the entire cerebral cortex. Since acetylcholine release in the cortex is increased both during REM and wake, the basocortical cholinergic system is believed to be involved in cortical desynchrony. In the current study, we analyzed the effect of cholinergic compounds injected into the forebrain structures of narcoleptic and control dogs. We found that carbachol (a cholinergic agonist) injected into the BF triggers cataplexy in narcoleptic dogs while it increases wakefulness in control dogs. Much higher doses of carbachol bilaterally injected in the BF were, however, shown to trigger muscle atonia even in control dogs. These results suggest that a cholinoceptive site in the BF is critically implicated in triggering muscle atonia and cataplexy. Together with similar results previously obtained in the pontine brainstem, it appears that a widespread hypersensitivity to cholinergic stimulation may be central to the pathophysiology of canine narcolepsy.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1995RJ66200008
View details for PubMedID 7623112
Pharmacological studies using a canine model of narcolepsy have demonstrated that adrenergic rather than serotonergic or dopaminergic uptake inhibition is the primary mode of action of antidepressants on cataplexy, a pathological manifestation of rapid eye movement (REM) sleep atonia that occurs in narcolepsy. This result is in line with the known involvement of adrenergic systems in the regulation of REM sleep. However, the lack of anticataplectic effects of selective serotonergic compounds was puzzling as serotonergic neurons of the dorsal raphe nuclei are known to decrease activity during the REM sleep in a manner similar to the adrenergic neurons of the locus coeruleus. To further explore the role of serotonergic systems, we tested the effect on canine cataplexy of six 5-HT1A agonists and five 5-HT1A antagonists. Results indicate that 5-HT1A agonists significantly suppress cataplexy in correlation with their in vitro affinities to the canine central 5-HT1A receptors. Anticataplectic effects were, however, accompanied by various behavioral changes, such as flattened body posture, increased panting and agitation. In contrast, the selective 5-HT1A antagonist did not aggravate cataplexy, although a 5-HT1A antagonist was able to block the anticataplectic effect of a 5-HT1A agonist. These results suggest that the anticataplectic effects of 5-HT1A agonists are truly mediated by 5-HT1A receptor stimulation. It is, however, likely that anticataplectic effects occur due to the behavioral side effects rather than the direct involvement of this receptor subtype in the regulation of cataplexy. Further studies are therefore necessary to address the question of whether these 5-HT1A agonists hold promise in the pharmacological treatment of human cataplexy.
View details for Web of Science ID A1995QL99500028
View details for PubMedID 7891329
Both rapid eye movement sleep and cataplexy in the narcoleptic canine have been shown to increase after both systemic and local administration of cholinergic agonists in the pontine reticular formation. Furthermore, binding studies indicate an increase in the number of M2 muscarinic receptors in the pontine reticular formation of narcoleptic canines. In the present study we have investigated the receptor subtypes involved in mediating the cholinergic stimulation of cataplexy, as defined by brief periods of hypotonia induced by emotions, within the pontine reticular formation of narcoleptic canines. Specific cholinergic and monoaminergic agonists and antagonists, and excitatory or inhibitory amino-acid neurotransmitter receptor agonists, were perfused through microdialysis probes implanted bilaterally in the pontine reticular formation of narcoleptic canines, and cataplexy was monitored using the Food-Elicited Cataplexy Test and recordings of electroencephalogram, electrooculogram and electromyogram. In narcoleptic canines, bilateral perfusion with oxotremorine (M2 muscarinic) (10(-5)-10(-3) M) in the pontine reticular formation produced a dose-dependent increase in cataplexy, which reached complete muscle atonia (status cataplecticus) during the highest concentration. In control canines bilateral perfusion with oxotremorine (10(-5)-10(-3) M) did not produce any cataplectic attacks, but did produce muscle atonia after the highest concentration. Bilateral perfusion with either McN-A-343 (M1 muscarinic) or nicotine (both 10(-5)-10(-3) M) did not have any effect on cataplexy in either narcoleptic or control canines. The increase in cataplexy in narcoleptic canines produced by local perfusion with carbachol (10(-4) M) followed by equimolar perfusion with a muscarinic antagonist was rapidly reversed by atropine (muscarinic) and gallamine (M2 muscarinic), partially reversed by 4-DAMP (M3/M1 muscarinic) and completely unaffected by pirenzepine (M1 muscarinic). Bilateral perfusion with excitatory, glutamatergic receptor agonists N-methyl-D-aspartate, AMPA (both at 10(-4)-10(-3) M) and kainic acid (10(-5)-10(-4) M) did not have any effect on cataplexy, whereas bilateral perfusion with the inhibitory GABAergic receptor agonist muscimol (10(-4)-10(-3) M) produced a moderate increase in cataplexy in the narcoleptic canines. Bilateral perfusion with numerous monoaminergic compounds, BHT-920 (alpha-2 agonist), yohimbine (alpha-2 antagonist), propranolol (beta antagonist) and prazosin (alpha-1 antagonist), did not have any effect on cataplexy. These findings demonstrate that cholinergic regulation of cataplexy in the narcoleptic canine at the level of the pontine reticular formation is mediated by M2, and possibly M3, muscarinic receptors. The effects of muscimol indicate that the stimulation of cataplexy might be elicited by local neuronal inhibition.
View details for Web of Science ID A1994PE28600005
View details for PubMedID 7991953
Cataplexy in the narcoleptic canine has been shown to increase after systemic administration of cholinergic agonists. Furthermore, the number of cholinergic receptors in the pontine reticular formation of narcoleptic canines is significantly elevated. In the present study we have investigated the effects of cholinergic drugs administered directly into the pontine reticular formation on cataplexy, as defined by brief episodes of hypotonia induced by emotions, in narcoleptic canines. Carbachol and atropine were perfused through microdialysis probes implanted bilaterally in the pontine reticular formation of freely moving, narcoleptic and control Doberman pinschers. Cataplexy was quantified using the Food-Elicited Cataplexy Test, and analysed using recordings of electroencephalogram, electrooculogram and electromyogram. Cataplexy was characterized by a desynchronized electroencephalogram and a drop in electromyogram and electrooculogram activity. In narcoleptic canines, both unilateral and bilateral carbachol (10(-5) to 10(-3) M) produced a dose-dependent increase in cataplexy, which resulted in complete muscle tone suppression at the highest concentration. In control canines, neither bilateral nor unilateral carbachol (10(-5) to 10(-3) M) produced cataplexy, although bilateral carbachol, did produce muscle atonia at the highest dose (10(-3)). The increase in cataplexy after bilateral carbachol (10(-4) M) was rapidly reversed when the perfusion medium was switched to one containing atropine (10(-4) M). Bilateral atropine (10(-3) to 10(-2) M) alone did not produce any significant effects on cataplexy in narcoleptic canines; however, bilateral atropine (10(-2) M) did reduce the increase in cataplexy produced by systemic administration of physostigmine (0.05 mg/kg, i.v.). These findings demonstrate that cataplexy in narcoleptic canines can be stimulated by applying cholinergic agonists directly into the pontine reticular formation. The ability of atropine to inhibit locally and systemically stimulated cataplexy indicates that the pontine reticular formation is a critical component in cholinergic stimulation of cataplexy. Therefore, it is suggested that the pontine reticular formation plays a significant role in the cholinergic regulation of narcolepsy.
View details for Web of Science ID A1994NF79800003
View details for PubMedID 8008205
Our series of pharmacological studies on canine narcolepsy has suggested that the adrenergic systems are more critically involved in the regulation of cataplexy than the serotonergic and dopaminergic systems. This, however, is an apparent contradiction to data obtained in human patients, which show that chronic oral administration of serotonergic uptake inhibitors, such as clomipramine, zimelidine and fluoxetine, is effective in reducing cataplexy. To explore this discrepancy, we have assessed the anticataplectic effects of various serotonergic uptake inhibitors and their active desmethyl metabolites on canine cataplexy. We found that the anticataplectic effect of the desmethyl metabolites, which are usually more potent for in vitro adrenergic uptake inhibition, was more potent and developed more rapidly than the effect of the parent compounds. Furthermore, the anticataplectic potency was positively correlated to the adrenergic uptake inhibition and was negatively correlated with serotonergic uptake inhibition among the 10 compounds tested. These results are consistent with our hypothesis of a preferential involvement of the adrenergic system in the control of cataplexy. Our results also suggest that the anticataplectic effect of "selective" serotonergic uptake inhibitors in human narcolepsy might be mediated by their less selective active metabolites.
View details for Web of Science ID A1993MV96900004
View details for PubMedID 8165384
Narcolepsy is currently treated with anti-depressants to control REM-related symptoms such as cataplexy and with amphetamine-like stimulants for the management of sleepiness. Both stimulant and antidepressant drugs presynaptically enhance monoaminergic transmission but both classes of compounds lack pharmacological specificity. In order to determine which monoamine is selectively involved in the therapeutic effect of these compounds, we examined the effects of selective monoamine uptake inhibitors and release enhancers on cataplexy using a canine model of the human disorder. A total of 14 compounds acting on the adrenergic (desipramine, nisoxetine, nortriptyline, tomoxetine, viloxazine), serotoninergic (fenfluramine, fluoxetine, indalpine, paroxetine, zimelidine) and dopaminergic (amfonelic acid, amineptine, bupropion, GBR 12909) systems were tested. Some additional compounds interesting clinically but with less pharmacological selectivity, i.e., cocaine, dextroamphetamine, methylphenidate, nomifensine and pemoline, were also included in the study. All compounds affecting noradrenergic transmission completely suppressed canine cataplexy at low doses in all dogs tested, whereas compounds which predominantly modified serotoninergic and dopaminergic transmission were either inactive or partially active at high doses. Our results demonstrate the preferential involvement of adrenergic systems in the control of cataplexy and, presumably, REM sleep atonia. Our findings also demonstrate that canine narcolepsy is a useful tool in assessing the pharmacological specificity of antidepressant drugs.
View details for Web of Science ID A1993MG37200013
View details for PubMedID 7862832
We have demonstrated previously that central noradrenergic mechanisms, especially postsynaptic alpha-1 receptors, are critically involved in the regulation of cataplexy, a pathological manifestation of rapid eye movement sleep atonia in narcolepsy. However, it has been shown recently that alpha-1 receptors constitute a heterogeneous population of binding sites, which is encoded by several distinct genes. In light of these findings, we investigated the possibility that the effect of alpha-1 compounds on cataplexy found in our previous study is mediated more specifically by certain alpha-1 receptor subtypes than by other subtypes. We therefore examined the effects of eight selective alpha-1 antagonists and five agonists on canine cataplexy and compared these with the affinities of the same compounds for the canine central alpha-1a and alpha-1b subtypes. The affinities of the compounds for the alpha-1 receptor subtypes were assessed by using [3H]prazosin receptor binding in combination with a 5-methylurapidil (an alpha-1a selective ligand) mask. Six of the eight alpha-1 antagonists tested exacerbated canine cataplexy, whereas all five agonists tested suppressed cataplexy. Furthermore, the potency (ED50 values) of the compounds on cataplexy significantly correlated with the affinity of the compounds for the alpha-1b binding site. These results are consistent with our earlier implication of the alpha-1 receptor mechanisms in the control of cataplexy and further suggest a specific involvement of the alpha-1b receptor subtype in these mechanisms.
View details for Web of Science ID A1993KT84600009
View details for PubMedID 8095546
Narcolepsy is a genetically determined disorder of sleep characterized by excessive daytime sleepiness and abnormal manifestations of REM sleep that affects both humans and animals. Although its exact pathophysiologic mechanisms remain undetermined, recent experiments have demonstrated that in both humans and canines, susceptibility genes are linked with immune-related genes. A striking difference, however, is that the genes thought to be involved in the human pathology are autosomal dominant, whereas canine narcolepsy in Dobermans is transmitted as a single autosomal recessive gene with full penetrance (canarc-1). In this study, we have examined the development of narcoleptic symptoms in homozygous narcoleptic, heterozygous, and control Dobermans. Animals were behaviorally observed until 5 months of age and then treated at weekly intervals with cataplexy-inducing compounds that act on cholinergic or monoaminergic systems (alone and in combination). Our data indicate that cataplexy can be induced in 6-month-old asymptomatic heterozygous animals, but not in control canines, with a combination of drugs that act on the monoaminergic and cholinergic systems. This demonstrates that disease susceptibility may be carried by heterozygosity at the canarc-1 locus. Our data further suggest that cataplexy, a model of REM sleep atonia, is centrally regulated by a balance of activity between cholinergic and monoaminergic neurons.
View details for Web of Science ID A1993KP71100016
View details for PubMedID 8095066
Canine narcolepsy is an animal model of the human rapid eye movement sleep disorder. Dogs exhibit bouts of sleep attacks and muscle atonia (cataplexy) that are induced by emotions and thought to be abnormal rapid eye movement sleep episodes. We have previously demonstrated that cataplexy is strongly inhibited by increases in noradrenergic activity. This effect is mediated through central alpha 1-adrenoceptors, presumably of the alpha 1B subtype. In this study, we demonstrate with the canine model that SDZ NVI-085, a new compound with alerting effects, is a potent anticataplectic agent that may act through stimulation of an alpha 1-adrenoceptor subtype.
View details for Web of Science ID A1991GU07700003
View details for PubMedID 1687464
Narcolepsy is a sleep disorder characterized by abnormal manifestations of rapid-eye-movement (REM) sleep and excessive daytime sleepiness. Using a canine model of the disease, we found that central D2 antagonists suppressed cataplexy, a form of REM-sleep atonia occurring in narcolepsy, whereas this symptom was aggravated by D2 agonists. The effect on cataplexy was stereospecific for the S(-) enantiomer of sulpiride (a D2 antagonist) and the R(+) enantiomer of 3-PPP (a D2 agonist). There was also a significant correlation between the in vivo pharmacological potency and in vitro drug affinity for D2 receptors (but not for D1 and alpha 2 receptors) among the seven central D2 antagonists tested. Selective D1 compounds were also tested; however, the results were inconsistent because both antagonists and agonists generally suppressed cataplexy. Our current results demonstrate that central D2-type receptors are critically involved in the control of cataplexy and REM sleep. Furthermore, the finding that small doses of D2 antagonists suppressed cataplexy and induced behavioral excitation, while small doses of D2 agonists aggravated cataplexy and induced sedation, suggests that this effect is mediated presynaptically. However, considering the fact that selective dopamine reuptake inhibitors did not modify cataplexy and that our previous pharmacological results demonstrated a preferential involvement of the noradrenergic system in the control of cataplexy, we believe that the effect of D2 compounds on cataplexy is mediated secondarily via the noradrenergic systems.
View details for Web of Science ID A1991GE83100004
View details for PubMedID 1831837
We have recently established that canine narcolepsy (an autosomal recessive genetic model of the human disorder) is dramatically improved by treatment with alpha 2 antagonists such as yohimbine (Nishino et al: J Pharmacol Exp Ther 253:1145-1152, 1990). To further investigate the role of alpha 2 adrenoceptors in narcolepsy, receptors labeled with [3H] yohimbine were examined on platelets from human and canine narcoleptic subjects. Twenty-eight Doberman pinschers were studied, 7 controls (C), 7 heterozygous (Hz), and 14 narcoleptics (N) (age and sex matched), including eight animals born in a backcross setting (narcoleptic x heterozygous; 5 narcoleptics and 3 heterozygous). The Kd and Bmax of each group respectively, were as follows: C, Kd = 2.86 +/- 0.76 nmol/L, Bmax = 295.78 +/- 31.89 fmol/mg protein; Hz, Kd = 2.06 +/- 0.23 nmol/L, Bmax = 307.02 +/- 22.21 fmol/mg protein; and N, Kd = 2.72 +/- 0.45 nmol/L, Bmax = 267.52 +/- 19.47 fmol/mg protein. No statistical differences were found between groups using nonparametric (Kruskall-Wallis) statistical procedures, and there were no correlations between any binding parameter and symptom severity within the narcoleptic group. Platelet alpha 2 receptor affinity and density also did not differ between narcoleptic and heterozygous dogs in the backcross litter (N [n = 5], Kd = 1.94 +/- 0.59 nmol/L, Bmax = 290.6 +/- 64.7 fmol/mg protein; Hz [n = 3], Kd = 2.83 +/- 0.47 nmol/L, Bmax = 294.2 +/- 42.9 fmol/mg protein). Fourteen human subjects, seven control and seven narcoleptic patients (age and sex matched), were included in the study.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1991EZ69000008
View details for PubMedID 1645207
It has been shown that endogenous prostaglandin D2 and prostaglandin E2 (PGE2) are involved in sleep-wake regulation. Our recent experimental result that exogenously administered PGE2 significantly reduces canine cataplexy (a pathological equivalent of rapid-eye-movement sleep atonia and a symptom of narcolepsy) suggests that PGE2 is involved in the pathophysiology of canine narcolepsy. In order to further investigate the role of prostaglandins (PGs) in this disorder, PG levels in cerebrospinal fluid (CSF) of genetically homozygous narcoleptic, heterozygous (unaffected), and control Doberman pinschers were studied. PGE2 levels were measured by direct radioimmunoassay (RIA) and after high-grade purification using PG affinity columns and high-performance liquid chromatography. PGD2 and PGF2 alpha levels were measured by RIA after high-grade purification. There was no significant difference in PGE2 levels between homozygous narcoleptic and heterozygous or controls dogs, and PGD2 and PGF2 alpha levels were undetectable in most cases. Our results do not favor the hypothesis that central PGE2 levels are modified in canine narcolepsy, assuming that PGE2 levels in cisternal CSF properly reflect PGE2 production in the brain.
View details for Web of Science ID A1990EJ24100006
View details for PubMedID 2268692
Recent experiments have demonstrated that pharmacological activation of central noradrenergic systems by monoaminergic stimulators or uptake blockers or through the stimulation of alpha-1 adrenergic receptors improved cataplexy, a major symptom of narcolepsy. In order to further the understanding of the control of cataplexy by noradrenergic mechanisms, the involvement of central alpha-2 adrenoceptors was examined in genetically narcoleptic Doberman pinschers using in vivo pharmacology. Yohimbine (1.5-96.0 micrograms/kg i.v.) and seven other selective and centrally acting alpha-2 adrenoceptor antagonists (rauwolscine: 1.5-96 micrograms/kg i.v.; atipemazole: 1.5-96 micrograms/kg i.v.; Wy-25309: 1.5-386 micrograms/kg i.v.; CGS-7525A: 1.5-386 micrograms/kg i.v.; idazoxan, 6-1536 micrograms/kg i.v.; piperoxan, 6-1536 micrograms/kg i.v.; and mianserin, 6-1536 micrograms/kg i.v.) significantly suppressed cataplexy. The alpha-2 mediation of this effect was demonstrated by a close correlation between drug affinities (Ki) toward the alpha-2 site (defined using [3H]yohimbine in canine cortex) and the ability of these drugs to reduce cataplexy [ED50 in nanomoles per kilogram i.v.) (r2 = 0.71, n = 8, P less than .01). The effects of six centrally acting alpha-2 agonists on canine cataplexy were also examined and two groups of compounds were distinguished on the basis of their pharmacological profile. Classical alpha-2 agonists such as clonidine (0.0625-4.0 micrograms/kg i.v.), p-aminoclonidine (0.0625-4.0 micrograms/kg i.v.) and guanfacine (0.0625-4.0 micrograms/kg i.v.) had no effect on cataplexy whereas BHT-920 (0.01875-3.0 micrograms/kg i.v.), BHT-933 (16.0-258 micrograms/kg i.v.) and xylazine (16.0-258 micrograms/kg i.v.) dramatically aggravated cataplexy.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1990DK70200035
View details for PubMedID 1972749
alpha 2-Receptors in the canine brain were pharmacologically characterized using [3H]yohimbine binding. Competition studies revealed a single class of binding sites in frontal cortex but two distinct subtypes in nucleus caudatus. The role of central alpha 2-receptors in narcolepsy was investigated in 5 normal and 5 narcoleptic Doberman pinschers. Scatchard analysis of [3H]yohimbine binding in different brain areas revealed an increase in the number of alpha 2-binding sites limited to the locus coeruleus. This suggests that altered autoinhibition of norepinephrine release may be associated with the narcoleptic symptomatology.
View details for Web of Science ID A1989AX91400023
View details for PubMedID 2557958
The present study suggests the specific involvement within the central nervous system of an alpha 1 adrenoceptor subtype in a behavior, the control of cataplexy, a pathological analogue of rapid eye movement (REM) sleep atonia. Experiments have shown that prazosin, an alpha 1 antagonist, dramatically aggravates canine narcolepsy-cataplexy through a central mechanism, and that [3H]prazosin binding sites are increased in the amygdala of narcoleptic dogs. However, the corresponding Scatchard plots were curvilinear and best fit was obtained with a two-site model, suggesting the existence of two [3H]prazosin binding sites. These two sites (high and low affinity [3H]prazosin binding sites) met the criteria for authentic receptors and were respectively very similar to the alpha 1a and alpha 1b (high and low affinity for WB4101, respectively) subtypes recently described in the rat and rabbit. Our results of in vivo pharmacology and in vitro [3H]prazosin binding in canine narcolepsy now clearly implicate the low affinity [3H]prazosin binding site (alpha 1b) in canine narcolepsy: (1) Prazosin, an alpha 1 antagonist with similar affinity for both subtypes, was much more potent in increasing cataplexy than WB4101, a compound with more affinity for the alpha 1a receptor. (2) Chlorethylclonidine and phenoxybenzamine, two irreversible blockers of the alpha 1 receptors with more affinity for the alpha 1b receptors, aggravate cataplexy for up to two weeks. (3) The alpha 1 receptor upregulation previously reported by our group in the amygdala of narcoleptic dogs was due to a selective increase in the low affinity [3H]prazosin binding sites. A role for noradrenaline in REM sleep regulation has been suspected for many years, but has never been clearly elucidated.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1989AC86100027
View details for PubMedID 2569353
The effects of intravenous administration of prostaglandins (PGs) were investigated in genetically narcoleptic Doberman pinschers. The treatment of narcoleptic dogs with PGE2 and PGE2 methyl ester, but not PGD2 and PGD2 methyl ester, induced a dose-dependent reduction of canine cataplexy, a dissociated manifestation of rapid-eye-movement sleep. The effect was specific and not associated with any change in other behavior. Furthermore, the effect was long-lasting (up to 2 hr) and could not be explained by the acute cardiovascular changes seen after intravenous PG administration. PGE2 methyl ester, a lipophilic derivative of PGE2 with more central penetration than PGE2, was 4 times more potent than PGE2. These results indicate that PGE2 modifies cataplexy through a central effect and suggest that this prostaglandin may play a role in rapid-eye-movement sleep regulation.
View details for Web of Science ID A1989U042300075
View details for PubMedID 2928344
Periodic leg movements during sleep (PLMS) is a high prevalent sleep disorder of unknown etiology. The disease is pharmacologically treated with dopaminergic agonists (i.e. D2/D3 agonists) and opiates. Periodic leg movements during sleep often occur in narcoleptic patients. We observed that narcoleptic canines, like narcoleptic humans, also exhibit jerky, unilateral or bilateral slow leg movements during sleep. The movements in dogs are characterized by repetitive dorsiflexions of the ankle, lasting 0.5-1.5 s, and occur at regular intervals of 3-20 s, thus showing similarities to PLMS in humans. The observation that D2/D3 agonists aggravate cataplexy in narcoleptic dogs suggests that altered dopaminergic regulation in canine narcolepsy may play a critical role in both cataplexy and PLMS. Our canines may therefore be an invaluable resource in PLMS research.
View details for Web of Science ID 000169754800033
View details for PubMedID 11422858
It is believed that narcolepsy involves abnormalities of rapid eye movement (REM) sleep, especially of REM sleep atonia. Compelling evidence suggests that the regulation of REM sleep and REM sleep atonia involves a reciprocal interaction of cholinergic and monoaminergic systems. Using our canine model of narcolepsy and a pharmacological approach, we have previously demonstrated a similar interaction in the regulation of cataplexy. Global activation of cholinergic or monoaminergic transmission aggravates or suppresses canine cataplexy, respectively. We have also identified the subtypes of monoaminergic and cholinergic receptors specifically involved in this interaction. Cataplexy is aggravated by activation of the cholinergic system via M2 stimulation, as well as deactivation of the catecholaminergic systems by either blockade of postsynaptic alpha-1b receptors or stimulation of alpha-2 or D2 inhibitory autoreceptors. These pharmacological results correspond to previously identified neurochemical abnormalities in canine narcolepsy, such as significant increases in M2 receptors in the pons, alpha-1 receptors in the amygdala, alpha-2 receptors in the locus coeruleus and D2 receptors in the amygdala and nucleus accumbens, when compared to control animals. Using local perfusion of active compounds, we have further demonstrated that cholinoceptive sites in the pontine reticular formation, as well as in the basal forebrain, are involved in the regulation of cataplexy. Although the specific sites of action of the monoaminergic compounds remain unknown, the results of our pharmacological and neurochemical studies to date suggest that a widespread hyperactivity of cholinergic systems within the central nervous system together with a hypoactivity of catecholaminergic systems underlie the pathophysiology of narcolepsy.
View details for Web of Science ID A1994QD08100016
View details for PubMedID 7701206