Decades of research have implicated the ventral tegmental area (VTA) in motivation, learning and reward processing. We and others recently demonstrated that it also serves as an important node in sleep/wake regulation. Specifically, VTA-dopaminergic neuron activation is sufficient to drive wakefulness and necessary for the maintenance of wakefulness. However, the role of VTA-GABAergic neurons in arousal regulation is not fully understood. It is still unclear whether VTA-GABAergic neurons predictably alter their activity across arousal states, what is the nature of interactions between VTA-GABAergic activity and cortical oscillations, and how activity in VTA-GABAergic neurons relates to VTA-dopaminergic neurons in the context of sleep/wake regulation. To address these, we simultaneously recorded population activity from VTA-subpopulations and EEG/EMG signals during spontaneous sleep/wake states and in the presence of salient stimuli in freely-behaving mice. We found that VTA-GABAergic neurons exhibit robust arousal-state-dependent alterations in population activity, with high activity and transients during wakefulness and REM sleep. During wakefulness, population activity of VTA-GABAergic neurons, but not VTA-dopaminergic neurons, was positively correlated with EEG gamma power and negatively correlated with theta power. During NREM sleep, population activity in both VTA-GABAergic and VTA-dopaminergic neurons negatively correlated with delta, theta, and sigma power bands. Salient stimuli, with both positive and negative valence, activated VTA-GABAergic neurons. Together, our data indicate that VTA-GABAergic neurons, like their dopaminergic counterparts, drastically alter their activity across sleep-wake states. Changes in their activity predicts cortical oscillatory patterns reflected in the EEG, which are distinct from EEG spectra associated with dopaminergic neural activity.Statement of Significance Little is known about how ventral tegmental area (VTA) neural ensembles couple arousal to motivated behaviors. Using cell-type specific genetic tools, we investigated the population activity of GABAergic and dopaminergic neurons within the VTA across sleep/wake states and in the presence of salient stimuli. We demonstrate that coordinated neural activity within VTA-GABAergic neurons peaks during wakefulness and REM sleep. Furthermore, neuronal activity in VTA-GABAergic neurons is correlated with high frequency, low amplitude cortical oscillations during waking, but negatively correlated with high amplitude slower frequency oscillations during NREM sleep. Our results demonstrate that VTA-GABAergic neuronal activity is tightly linked to cortical arousal and highlight this population as a potential important node in sleep/wake regulation.
View details for DOI 10.1523/ENEURO.0356-19.2020
View details for PubMedID 32054621
Alcohol use disorder (AUD) is a difficult to treat condition with a significant global public health and cost burden. The nucleus accumbens (NAc) has been implicated in AUD and identified as an ideal target for deep brain stimulation (DBS). There are promising preclinical animal studies of DBS for alcohol consumption as well as some initial human clinical studies that have shown some promise at reducing alcohol-related cravings and, in some instances, achieving long-term abstinence. In this review, the authors discuss the evidence and concepts supporting the role of the NAc in AUD, summarize the findings from published NAc DBS studies in animal models and humans, and consider the challenges and propose future directions for neuromodulation of the NAc for the treatment of AUD.
View details for PubMedID 30064314
Lateral hypothalamus (LH) neurons containing the neuropeptide hypocretin (HCRT; orexin) modulate affective components of arousal, but their relevant synaptic inputs remain poorly defined. Here we identified inputs onto LH neurons that originate from neuronal populations in the bed nuclei of stria terminalis (BNST; a heterogeneous region of extended amygdala). We characterized two non-overlapping LH-projecting GABAergic BNST subpopulations that express distinct neuropeptides (corticotropin-releasing factor, CRF, and cholecystokinin, CCK). To functionally interrogate BNSTLH circuitry, we used tools for monitoring and manipulating neural activity with cell-type-specific resolution in freely behaving mice. We found that Crf-BNST and Cck-BNST neurons respectively provide abundant and sparse inputs onto Hcrt-LH neurons, display discrete physiological responses to salient stimuli, drive opposite emotionally valenced behaviors, and receive different proportions of inputs from upstream networks. Together, our data provide an advanced model for how parallel BNSTLH pathways promote divergent emotional states via connectivity patterns of genetically defined, circuit-specific neuronal subpopulations.
View details for PubMedID 30038273
The present study investigated the function of Hypocretin (Hcrt or Orexin/OX) receptor antagonists in sleep modulation and memory function with optical methods in transgenic mice.We used Hcrt-IRES-Cre knock-in mice and AAV vectors expressing channelrhodopsin-2 (ChR2) to render Hcrt neurons sensitive to blue light stimulation. We optogenetically stimulated Hcrt neurons and measured latencies to wakefulness in the presence or absence of OX1/2R antagonists and Zolpidem. We also examined endogenous Hcrt neuronal activity with fiber photometry. Changes in memory after optogenetic sleep disruption were evaluated by the novel object recognition test (NOR) and compared for groups treated with vehicle, OX1/2R antagonists, or Zolpidem. We also analyzed EEG power spectra of wakefulness, rapid eye movement (REM) sleep, and non-REM (NREM) sleep following the injections of vehicle, OX1/2R antagonists, and Zolpidem in young adult mice.Acute optogenetic stimulation of Hcrt neurons at different frequencies resulted in wakefulness. Treatment with dual OX1/2R antagonists (DORAs) DORA12 and MK6096, as well as selective OX2R antagonist MK1064 and Zolpidem, but not selective OX1R antagonist 1SORA1, significantly reduced the bout length of optogenetic stimulation-evoked wakefulness episode. Fiber photometry recordings of GCaMP6f signals showed that Hcrt neurons are active during wakefulness, even in the presence of OXR antagonists. Treatment with dual OX1/2R antagonists improved memory function despite optogenetic sleep fragmentation caused impaired memory function in a NOR test.Our results show DORAs and selective OX2R antagonists stabilize sleep and improve sleep-dependent cognitive processes even when challenged by optogenetic stimulation mimicking highly arousing stimuli.
View details for PubMedID 30060151
Dopaminergic ventral tegmental area (VTA) neurons are critically involved in a variety of behaviors that rely on heightened arousal, but whether they directly and causally control the generation and maintenance of wakefulness is unknown. We recorded calcium activity using fiber photometry in freely behaving mice and found arousal-state-dependent alterations in VTA dopaminergic neurons. We used chemogenetic and optogenetic manipulations together with polysomnographic recordings to demonstrate that VTA dopaminergic neurons are necessary for arousal and that their inhibition suppresses wakefulness, even in the face of ethologically relevant salient stimuli. Nevertheless, before inducing sleep, inhibition of VTA dopaminergic neurons promoted goal-directed and sleep-related nesting behavior. Optogenetic stimulation, in contrast, initiated and maintained wakefulness and suppressed sleep and sleep-related nesting behavior. We further found that different projections of VTA dopaminergic neurons differentially modulate arousal. Collectively, our findings uncover a fundamental role for VTA dopaminergic circuitry in the maintenance of the awake state and ethologically relevant sleep-related behaviors.
View details for DOI 10.1038/nn.4377
View details for PubMedID 27595385
Hypocretin (also known as orexin) is a peptide neuromodulator that is expressed exclusively in the lateral hypothalamic area and plays a fundamental role in wakefulness and arousal. Chronic stress and compulsive drug-seeking are two examples of dysregulated states of hyperarousal that are influenced by hypocretin transmission throughout hypothalamic, extended amygdala, brainstem, and mesolimbic pathways. Here, we review current advances in the understanding of hypocretin's modulatory actions underlying conditions of negative and positive emotional valence, focusing particularly on mechanisms that facilitate adaptive (and maladaptive) responses to stressful or rewarding environmental stimuli. We conclude by discussing progress toward integrated theories for hypocretin modulation of divergent behavioral domains.
View details for DOI 10.1016/j.conb.2014.07.006
View details for Web of Science ID 000347128200015
View details for PubMedID 25050887
View details for PubMedCentralID PMC4267967
Addictive disorders are chronic, relapsing conditions that cause extensive disease burden. Genetic factors partly account for susceptibility to addiction, but environmental factors such as stressful experiences and prolonged exposure of the brain to addictive drugs promote its development. Progression to addiction involves neuroadaptations within neurocircuitry that mediates stress responses and is influenced by several peptidergic neuromodulators. While corticotrophin releasing factor is the prototypic member of this class, recent work has identified several additional stress-related neuropeptides that play an important role in regulation of drug intake and relapse, including the urocortins, nociceptin, substance P, and neuropeptide S. Here, we review this emerging literature, discussing to what extent the properties of these neuromodulators are shared or distinct and considering their potential as drug targets.
View details for DOI 10.1016/j.neuron.2012.09.026
View details for Web of Science ID 000309799000014
View details for PubMedID 23040815
View details for PubMedCentralID PMC3495179
View details for DOI 10.1038/nrn3110-c1
View details for PubMedID 22183439
Daily, animals need to decide when to stop engaging in cognitive processes and behavioral responses to the environment, and go to sleep. The main processes regulating the daily organization of sleep and wakefulness are circadian rhythms and homeostatic sleep pressure. In addition, motivational processes such as food seeking and predator evasion can modulate sleep/wake behaviors. Here, we discuss the principal processes regulating the propensity to stay awake or go to sleep-focusing on neuronal and behavioral aspects. We first introduce the neuronal populations involved in sleep/wake regulation. Next, we describe the circadian and homeostatic drives for sleep. Then, we highlight studies demonstrating various effects of motivational processes on sleep/wake behaviors, and discuss possible neuronal mechanisms underlying their control.
View details for DOI 10.1016/j.conb.2017.04.010
View details for PubMedID 28500869
The corticotropin-releasing factor (CRF) system plays a role in alcohol consumption, and its dysregulation can contribute to alcohol use disorder. This system includes four peptide ligands: CRF, urocortin (Ucn)1, Ucn2, and Ucn3. Historically, attention focused on CRF, however, Ucn1 also plays a critical role in excessive alcohol use. This review covers evidence for this contribution and contrasts the role of Ucn1 with CRF. While CRF can promote binge consumption, this regulation occurs through generalized mechanisms that are not specific for alcohol. In contrast, inhibition of Ucn1 action specifically blunts escalation of alcohol drinking. Lesions, genetic knockout, and RNA interference experiments indicate that the centrally projecting Edinger-Westphal nucleus is the neuroanatomical source of Ucn1 critical for alcohol drinking. We propose that the contributions of Ucn1 to excessive drinking likely occur through enhancing rewarding properties of alcohol and symptoms of alcohol withdrawal, whereas CRF drives dependence-induced drinking at later stages of alcohol use. The transition from occasional binge drinking to dependence intricately depends on CRF system plasticity and coordination of CRF and Ucn1.
View details for PubMedID 29056154
How the brain controls vigilance state transitions remains to be fully understood. The discovery of hypocretins, also known as orexins, and their link to narcolepsy has undoubtedly allowed us to advance our knowledge on key mechanisms controlling the boundaries and transitions between sleep and wakefulness. Lack of function of hypocretin neurons (a relatively simple and non-redundant neuronal system) results in inappropriate control of sleep states without affecting the total amount of sleep or homeostatic mechanisms. Anatomical and functional evidence shows that the hypothalamic neurons that produce hypocretins/orexins project widely throughout the entire brain and interact with major neuromodulator systems in order to regulate physiological processes underlying wakefulness, attention, and emotions. Here, we review the role of hypocretins/orexins in arousal state transitions, and discuss possible mechanisms by which such a relatively small population of neurons controls fundamental brain state dynamics.
View details for DOI 10.1007/7854_2016_58
View details for PubMedID 28012091
View details for DOI 10.7554/eLife.12093
View details for Web of Science ID 000367511500001
View details for PubMedID 26651823
View details for PubMedCentralID PMC4744186
Several recent studies implementing the standard "drinking-in-the-dark" (DID) model of short-term binge-like ethanol (EtOH) intake in C57BL/6J mice highlighted a role for the stress-related neuropeptide corticotropin-releasing factor (CRF) and its primary binding partner, the CRF type-1 (CRF1) receptor.We evaluated the selectivity of CRF1 involvement in binge-like EtOH intake by interrupting CRF1 function via pharmacological and genetic methods in a slightly modified 2-bottle choice DID model that allowed calculation of an EtOH preference ratio. In addition to determining EtOH intake and preference, we also measured consumption of food and H2 O during the DID period, both in the presence and absence of EtOH and sweet tastant solutions.Treatment with either of the CRF1-selective antagonists CP-376,395 (CP; 10 to 20 mg/kg, i.p.) or NBI-27914 (10 to 30 mg/kg, i.p.) decreased intake of 15% EtOH in male C57BL/6J mice, but did so in the absence of a concomitant decrease in EtOH preference. These findings were replicated genetically in a CRF1 knockout (KO) mouse model (also on a C57BL/6J background). In contrast to effects on EtOH intake, pharmacological blockade of CRF1 with CP increased intake of 10% sucrose, consistent with previous findings in CRF1 KO mice. Finally, pharmacological and genetic disruption of CRF1 activity significantly reduced feeding and/or total caloric intake in all experiments, confirming the existence of nonspecific effects.Our findings indicate that blockade of CRF1 receptors does not exert specific effects on EtOH intake in the DID paradigm, and that slight modifications to this procedure, as well as additional consummatory control experiments, may be useful when evaluating the selectivity of pharmacological and genetic manipulations on binge-like EtOH intake.
View details for DOI 10.1111/acer.12076
View details for Web of Science ID 000321256800012
View details for PubMedID 23398267
View details for PubMedCentralID PMC3657581
It is widely accepted that stress, anxiety, depression and alcohol abuse-related disorders are in large part controlled by corticotropin-releasing factor (CRF) receptors. However, evidence is accumulating that some of the actions on these receptors are mediated not by CRF, but by a family of related Urocortin (Ucn) peptides Ucn1, Ucn2 and Ucn3. The initial narrow focus on CRF as the potential main player acting on CRF receptors appears outdated. Instead it is suggested that CRF and the individual Ucns act in a complementary and brain region-specific fashion to regulate anxiety-related behaviors and alcohol consumption. This review, based on a symposium held in 2011 at the research meeting on "Alcoholism and Stress" in Volterra, Italy, highlights recent evidence for regulation of these behaviors by Ucns. In studies on stress and anxiety, the roles of Ucns, and in particular Ucn1, appear more visible in experiments analyzing adaptation to stressors rather than testing basal anxiety states. Based on these studies, we propose that the contribution of Ucn1 to regulating mood follows a U-like pattern with both high and low activity of Ucn1 contributing to high anxiety states. In studies on alcohol use disorders, the CRF system appears to regulate not only dependence-induced drinking, but also binge drinking and even basal consumption of alcohol. While dependence-induced and binge drinking rely on the actions of CRF on CRFR1 receptors, alcohol consumption in models of these behaviors is inhibited by actions of Ucns on CRFR2. In contrast, alcohol preference is positively influenced by actions of Ucn1, which is capable of acting on both CRFR1 and CRFR2. Because of complex distribution of Ucns in the nervous system, advances in this field will critically depend on development of new tools allowing site-specific analyses of the roles of Ucns and CRF.
View details for DOI 10.1016/j.alcohol.2011.10.007
View details for PubMedID 22444954
Detailed examination of the midbrain Edinger-Westphal (EW) nucleus revealed the existence of two distinct nuclei. One population of EW preganglionic (EWpg) neurons was found to control oculomotor functions, and a separate population of EW centrally projecting (EWcp) neurons was found to contain stress- and feeding-related neuropeptides. Although it has been shown that EWcp neurons are highly responsive to drugs of abuse and behavioral stress, a genetic characterization of the EWcp was needed. To identify genetic differences in the EWcp of inbred mouse strains that differ in behaviors relevant to EWcp function, we used publicly available tools from the Allen Brain Atlas to identify 68 transcripts that were selectively expressed in the EWcp, and examined their expression within tissue punch microdissection samples containing the EWcp of adult male C57BL/6J (B6) and DBA/2J (D2) mice. Using 96-well quantitative real-time PCR (qPCR) arrays that included the EWcp-specific genes, several other genes of interest, and five housekeeping genes, we identified strain differences in expression of 11 EWcp-specific genes (BC023892, Btg3, Bves, Cart, Cck, Ghsr, Neto1, Postn, Ptprn, Rcn1, and Ucn), two immediate early genes (Egr1 and Fos), and one dopamine-related gene (Drd5). All significant expression differences were greater in B6 vs. D2 mice, and several of these were verified either at the protein level using immunohistochemistry (IHC) or in silico using microarray data sets from whole brain and other brain areas. These results demonstrate a significant advance in our understanding of the EWcp on three levels. First, we generated a list of EWcp-specific genes (most of which had not yet been reported within the EWcp in the literature) that will be informative for future studies of EWcp function. Second, due to similarity in results from qPCR and IHC, we revealed that strain differences in basal EWcp neuropeptide content are accounted for by differential transcription and number of peptidergic neurons, rather than by differential rates of peptide release. And third, our identification of differentially expressed EWcp-specific genes between B6 and D2 mice may hold powerful insight into the neurogenetic contributions of the EWcp to stress- and addiction-related behaviors.
View details for DOI 10.3389/fnana.2012.00005
View details for Web of Science ID 000300953500001
View details for PubMedID 22347848
View details for PubMedCentralID PMC3278674
Enhanced sensitivity to the euphoric and locomotor-activating effects of psychostimulants may influence an individual's predisposition to drug abuse and addiction. While drug-induced behaviors are mediated by the actions of several neurotransmitter systems, past research revealed that the corticotropin-releasing factor (CRF) system is important in driving the acute locomotor response to psychostimulants.We previously reported that genetic deletion of the CRF type-2 receptor (CRF-R2), but not the CRF type-1 receptor (CRF-R1) dampened the acute locomotor stimulant response to methamphetamine (1 mg/kg). These results contrasted with previous studies implicating CRF-R1 in the locomotor effects of psychostimulants. Since the majority of previous studies focused on cocaine, rather than methamphetamine, we set out to test the hypothesis that these drugs differentially engage CRF-R1 and CRF-R2.We expanded our earlier findings by first replicating our previous experiments at a higher dose of methamphetamine (2 mg/kg), and by assessing the effects of the CRF-R1-selective antagonist CP-376,395 (10 mg/kg) on methamphetamine-induced locomotor activity. Next, we used both genetic and pharmacological tools to examine the specific components of the CRF system underlying the acute locomotor response to cocaine (5-10 mg/kg).While genetic deletion of CRF-R2 dampened the locomotor response to methamphetamine (but not cocaine), genetic deletion and pharmacological blockade of CRF-R1 dampened the locomotor response to cocaine (but not methamphetamine).These findings highlight the differential involvement of CRF receptors in acute sensitivity to two different stimulant drugs of abuse, providing an intriguing basis for the development of more targeted therapeutics for psychostimulant addiction.
View details for DOI 10.1007/s00213-011-2433-y
View details for Web of Science ID 000300779900012
View details for PubMedID 21833501
View details for PubMedCentralID PMC3266955
Converging lines of evidence point to the involvement of neurons of the centrally projecting Edinger-Westphal nucleus (EWcp) containing the neuropeptide Urocortin-1 (Ucn1) in excessive ethanol (EtOH) intake and EtOH sensitivity. Here, we expanded these previous findings by using a continuous-access, two-bottle choice drinking paradigm (3%, 6%, and 10% EtOH vs. tap water) to compare EtOH intake and EtOH preference in Ucn1 genetic knockout (KO) and wild-type (WT) mice. Based on previous studies demonstrating that electrolytic lesion of the EWcp attenuated EtOH intake and preference in high-drinking C57BL/6J mice, we also set out to determine whether EWcp lesion would differentially alter EtOH consumption in Ucn1 KO and WT mice. Finally, we implemented well-established place conditioning procedures in KO and WT mice to determine whether Ucn1 and the corticotropin-releasing factor type-2 receptor (CRF-R2) were involved in the rewarding and aversive effects of EtOH (2 g/kg, i.p.). Results from these studies revealed that (1) genetic deletion of Ucn1 dampened EtOH preference only in mice with an intact EWcp, but not in mice that received lesion of the EWcp, (2) lesion of the EWcp dampened EtOH intake in Ucn1 KO and WT mice, but dampened EtOH preference only in WT mice expressing Ucn1, and (3) genetic deletion of Ucn1 or CRF-R2 abolished the conditioned rewarding effects of EtOH, but deletion of Ucn1 had no effect on the conditioned aversive effects of EtOH. The current findings provide strong support for the hypothesis that EWcp-Ucn1 neurons play an important role in EtOH intake, preference, and reward.
View details for DOI 10.1371/journal.pone.0026997
View details for Web of Science ID 000299081800056
View details for PubMedID 22046429
View details for PubMedCentralID PMC3203949
Sensitivity to the euphoric and locomotor-activating effects of drugs of abuse may contribute to risk for excessive use and addiction. Repeated administration of psychostimulants such as methamphetamine (MA) can result in neuroadaptive consequences that manifest behaviorally as a progressive escalation of locomotor activation, termed psychomotor sensitization. The present studies addressed the involvement of specific components of the corticotropin-releasing factor (CRF) system in locomotor activation and psychomotor sensitization induced by MA (1, 2 mg/kg) by utilizing pharmacological approaches, as well as a series of genetic knockout (KO) mice, each deficient for a single component of the CRF system: CRF-R1, CRF-R2, CRF, or the CRF-related peptide Urocortin 1 (Ucn1). CRF-R1 KO mice did not differ from wild-type mice in sensitization to MA, and pharmacological blockade of CRF-R1 with CP-154,526 (15, 30 mg/kg) in DBA/2J mice did not selectively attenuate either the acquisition or expression of MA-induced sensitization. Deletion of either of the endogenous ligands of CRF-R1 (CRF, Ucn1) either enhanced or had no effect on MA-induced sensitization, providing further evidence against a role for CRF-R1 signaling. Interestingly, deletion of CRF-R2 attenuated MA-induced locomotor activation, elucidating a novel contribution of the CRF system to MA sensitivity, and suggesting the participation of the endogenous urocortin peptides Ucn2 and Ucn3. Immunohistochemistry for Fos was used to visualize neural activation underlying CRF-R2-dependent sensitivity to MA, identifying the basolateral and central nuclei of the amygdala as neural substrates involved in this response. Our results support further examination of CRF-R2 involvement in neural processes associated with MA addiction.
View details for DOI 10.1111/j.1601-183X.2010.00641.x
View details for Web of Science ID 000286468900009
View details for PubMedID 20731720
View details for PubMedCentralID PMC3025045
Although stress has profound effects on motivated behavior, the underlying mechanisms responsible are incompletely understood. In this study we elucidate a functional pathway in mouse brain that encodes the aversive effects of stress and mediates stress-induced reinstatement of cocaine place preference (CPP). Activation of the dynorphin/kappa opioid receptor (KOR) system by either repeated stress or agonist produces conditioned place aversion (CPA). Because KOR inhibition of dopamine release in the mesolimbic pathway has been proposed to mediate the dysphoria underlying this response, we tested dopamine-deficient mice in this study and found that KOR agonist in these mice still produced CPA. However, inactivation of serotonergic KORs by injection of the KOR antagonist norBNI into the dorsal raphe nucleus (DRN), blocked aversive responses to the KOR agonist U50,488 and blocked stress-induced reinstatement of CPP. KOR knockout (KO) mice did not develop CPA to U50,488; however, lentiviral re-expression of KOR in the DRN of KOR KO mice restored place aversion. In contrast, lentiviral expression in DRN of a mutated form of KOR that fails to activate p38 MAPK required for KOR-dependent aversion, did not restore place aversion. DRN serotonergic neurons project broadly throughout the brain, but the inactivation of KOR in the nucleus accumbens (NAc) coupled with viral re-expression in the DRN of KOR KO mice demonstrated that aversion was encoded by a DRN to NAc projection. These results suggest that the adverse effects of stress may converge on the serotonergic system and offers an approach to controlling stress-induced dysphoria and relapse.
View details for DOI 10.1073/pnas.0910705106
View details for Web of Science ID 000271637500053
View details for PubMedID 19864633
View details for PubMedCentralID PMC2776420
Latest information on COVID-19
