All Publications

  • Cup tool use by squirrel monkeys AMERICAN JOURNAL OF PRIMATOLOGY Buckmaster, C. L., Hyde, S. A., Parker, K. J., Lyons, D. M. 2015

    View details for DOI 10.1002/ajp.22486

  • Plasma vasopressin concentrations positively predict cerebrospinal fluid vasopressin concentrations in human neonates. Peptides Carson, D. S., Howerton, C. L., Garner, J. P., Hyde, S. A., Clark, C. L., Hardan, A. Y., Penn, A. A., Parker, K. J. 2014; 61: 12-16


    Central arginine vasopressin (AVP) plays a critical role in mammalian social behavior and has been hypothesized to be a biomarker of certain human neurodevelopmental disorders, including autism. However, opportunities to collect post-mortem brain tissue or cerebrospinal fluid (CSF) from children are extremely limited, and the use of less invasive peripheral assessments (e.g., blood, urine, or saliva) of AVP as a proxy for more invasive central measures has not been well validated. Further, almost nothing is known about AVP biology in very young infants. Therefore in the present study we concomitantly collected basal CSF and plasma samples from N=20 neonates undergoing clinical sepsis evaluation (all were sepsis negative) and quantified AVP concentrations via well-validated enzyme-immunoassay methodology. Plasma AVP concentrations significantly and positively predicted CSF AVP concentrations (r=0.73, p=0.0021), and this relationship persisted when variance attributed to sex, gestational age, and sample collection time was controlled for in the statistical model (r=0.75, p=0.0047). These findings provide preliminary support for the use of basal plasma AVP measurement as a proxy for basal brain AVP activity in pediatric populations. Future studies are now required to determine the relationship between behavioral measures and AVP concentrations in both central and peripheral compartments in young infants and older children.

    View details for DOI 10.1016/j.peptides.2014.08.003

    View details for PubMedID 25148831

  • Plasma oxytocin concentrations and OXTR polymorphisms predict social impairments in children with and without autism spectrum disorder PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Parker, K. J., Garner, J. P., Libove, R. A., Hyde, S. A., Hornbeak, K. B., Carson, D. S., Liao, C., Phillips, J. M., Hallmayer, J. F., Hardan, A. Y. 2014; 111 (33): 12258-12263


    The neuropeptide oxytocin (OXT) and its receptor (OXTR) regulate social functioning in animals and humans. Initial clinical research suggests that dysregulated plasma OXT concentrations and/or OXTR SNPs may be biomarkers of social impairments in autism spectrum disorder (ASD). We do not know, however, whether OXT dysregulation is unique to ASD or whether OXT biology influences social functioning more generally, thus contributing to, but not causing, ASD phenotypes. To distinguish between these possibilities, we tested in a child ASD cohort, which included unaffected siblings and unrelated neurotypical controls (ages 3-12 y; n = 193), whether plasma OXT concentrations and OXTR SNPs (i) interact to produce ASD phenotypes, (ii) exert differential phenotypic effects in ASD vs. non-ASD children, or (iii) have similar phenotypic effects independent of disease status. In the largest cohort tested to date, we found no evidence to support the OXT deficit hypothesis of ASD. Rather, OXT concentrations strongly and positively predicted theory of mind and social communication performance in all groups. Furthermore, OXT concentrations showed significant heritability between ASD-discordant siblings (h(2) = 85.5%); a heritability estimate on par with that of height in humans. Finally, carriers of the "G" allele of rs53576 showed impaired affect recognition performance and carriers of the "A" allele of rs2254298 exhibited greater global social impairments in all groups. These findings indicate that OXT biology is not uniquely associated with ASD, but instead exerts independent, additive, and highly heritable influences on individual differences in human social functioning, including the severe social impairments which characterize ASD.

    View details for DOI 10.1073/pnas.1402236111

    View details for Web of Science ID 000340438800080

    View details for PubMedID 25092315

  • Plasma oxytocin concentrations are lower in depressed vs. healthy control women and are independent of cortisol JOURNAL OF PSYCHIATRIC RESEARCH Yuen, K. W., Garner, J. P., Carson, D. S., Keller, J., Lembke, A., Hyde, S. A., Kenna, H. A., Tennakoon, L., Schatzberg, A. F., Parker, K. J. 2014; 51: 30-36


    The neuropeptide oxytocin (OT) promotes social behavior and attenuates stress responsivity in mammals. Recent clinical evidence suggests OT concentrations may be dysregulated in major depression. This study extends previous research by testing whether: 1) OT concentrations vary systematically in depressive disorders with and without hypercortisolemia, 2) gender differences in OT concentrations are observed in depressed vs. healthy control participants, and 3) OT concentrations are predictive of clinical phenotypes. Plasma OT concentrations of psychotic major depressive (PMD; n = 14: 10 female, 4 male), non-psychotic major depressive (NPMD; n = 17: 12 female, 5 male), and non-depressed, healthy control (n = 19: 11 female, 8 male) participants were assayed at 2000, 2400, 0400, and 0800 h. Plasma cortisol concentrations were quantified at 2300 h, and clinical phenotypes were determined. As expected, PMD participants, compared to NPMD and healthy control participants, showed higher plasma cortisol concentrations. Although both depressed groups showed similar OT concentrations, a significant interaction effect between group and gender was observed. Specifically, depressed females exhibited lower mean OT concentrations than depressed males. Further, depressed vs. healthy control female participants exhibited lower mean OT concentrations, whereas depressed vs. healthy control male participants showed a trend in the opposite direction. OT concentrations were also predictive of desirability, drug dependence, and compulsivity scores as measured by the Million Clinical Multiaxial Inventory-III. All findings were independent of cortisol. These data suggest that OT signaling may provide a mechanism by which to better understand female-biased risk to develop depressive disorders and that plasma OT concentrations may be a useful biomarker of certain clinical phenotypes.

    View details for DOI 10.1016/j.jpsychires.2013.12.012

    View details for Web of Science ID 000332909500004

  • Cerebrospinal fluid and plasma oxytocin concentrations are positively correlated and negatively predict anxiety in children Molecular Psychiatry Carson, D. S., Berquist, S. W., Trujillo, T. H., Garner, J. P., Hannah, S. L., Hyde, S. A., Sumiyoshi, R. D., Jackson, L. P., Moss, J. K., Strehlow, M. C., Cheshier, S. H., Partap, S., Hardan, A. Y., Parker, K. J. 2014: 6

    View details for DOI 10.1038/mp.2014.132

  • Neonatal CSF oxytocin levels are associated with parent report of infant soothability and sociability PSYCHONEUROENDOCRINOLOGY Clark, C. L., St John, N., Pasca, A. M., Hyde, S. A., Hornbeak, K., Abramova, M., Feldman, H., Parker, K. J., Penn, A. A. 2013; 38 (7): 1208-1212


    Oxytocin (OT) has been linked to social behavior in rodents, non-human primates, and adult humans, but almost nothing is known about brain OT activity in human newborns or its impact on social development. To better understand the role of OT biology in human social functioning, a multi-disciplinary, longitudinal study was conducted. Cerebral spinal fluid (CSF) OT levels from 18 human neonates were evaluated and examined in relationship to social-seeking behavior at term, at 3 months, and at 6 months of age. Higher neonatal CSF OT levels were consistently associated with solicitation of parental soothing and interest in social engagement with others. This is the first study to link CSF OT levels to normative human social functioning. Research is now required to test whether early OT levels serve as a biomarker for subsequent social abnormalities.

    View details for DOI 10.1016/j.psyneuen.2012.10.017

    View details for Web of Science ID 000320412400026

  • A novel form of oxytocin in New World monkeys BIOLOGY LETTERS Lee, A. G., Cool, D. R., Grunwald, W. C., Neal, D. E., Buckmaster, C. L., Cheng, M. Y., Hyde, S. A., Lyons, D. M., Parker, K. J. 2011; 7 (4): 584-587


    Oxytocin is widely believed to be present and structurally identical in all placental mammals. Here, we report that multiple species of New World monkeys possess a novel form of oxytocin, [P8] oxytocin. This mutation arises from a substitution of a leucine to a proline in amino acid position 8. Further analysis of this mutation in Saimiri sciureus (squirrel monkey) indicates that [P8] oxytocin is transcribed and translated properly. This mutation is specific to oxytocin, as the peptide sequence for arginine vasopressin, a structurally related nonapeptide, is unaltered. These findings dispel the notion that all placental mammals possess a 'universal' oxytocin sequence, and highlight the need for research on the functional significance of this novel nonapeptide in New World monkeys.

    View details for DOI 10.1098/rsbl.2011.0107

    View details for Web of Science ID 000292639100031

    View details for PubMedID 21411453

  • Somatic and neuroendocrine responses to standard and biologically salient acoustic startle stimuli in monkeys PSYCHONEUROENDOCRINOLOGY Parker, K. J., Hyde, S. A., Buckmaster, C. L., Tanaka, S. M., Brewster, K. K., Schatzberg, A. F., Lyons, D. M., Woodward, S. H. 2011; 36 (4): 547-556


    The startle response, a simple defensive response to a sudden stimulus signaling proximal threat, has been well studied in rodents and humans, but has been rarely examined in monkeys. The first goal of the present studies was to develop a minimally immobilizing startle measurement paradigm and validate its usefulness by testing two core features of the startle response (habituation and graded responsivity) in squirrel monkey subjects. Two different types of startle stimuli were used: standard broad-band noise bursts, and species-specific alarm vocalizations ("yaps") which are elicited in response to threat in both wild and captive animals. The second goal of the present studies was to test whether yaps produce enhanced startle responsivity due to their increased biological salience compared to simple, non-biologically relevant noise bursts. The third goal of the present studies was to evaluate the hypothalamic-pituitary-adrenal (HPA) axis response to startle stimuli, as little is known about the stress-activating role of startle stimuli in any species. These experiments determined that the whole-body startle response in relatively unrestrained squirrel monkeys habituates across repeated stimulus presentations and is proportional to stimulus intensity. In addition, differential habituation was observed across biologically salient vs. standard acoustic startle stimuli. Responses to "yaps" were larger initially but attenuated more rapidly over trials. Responses to "yaps" were also larger in the early subepochs of the response window but then achieved a lower level than responses to noise bursts in the later subepochs. Finally, adrenocorticotropic hormone and cortisol concentrations were significantly elevated above baseline after startle stimuli presentation, though monkeys did not exhibit differential HPA axis responses to the two types of startle stimuli. The development of monkey startle methodology may further enhance the utility of this paradigm in translational studies of human stress-related psychiatric disorders.

    View details for DOI 10.1016/j.psyneuen.2010.08.009

    View details for Web of Science ID 000288922300013

    View details for PubMedID 20869176

  • Effects of Age on Cerebrospinal Fluid Oxytocin Levels in Free-Ranging Adult Female and Infant Rhesus Macaques BEHAVIORAL NEUROSCIENCE Parker, K. J., Hoffman, C. L., Hyde, S. A., Cummings, C. S., Maestripieri, D. 2010; 124 (3): 428-433


    There is growing interest in examining oxytocin and social functioning in human and non-human primates. Studies of human oxytocin biology are typically restricted to peripheral assessments because opportunities to collect cerebrospinal fluid (CSF) are rare. Several studies have examined CSF oxytocin levels in captive adult primates, but none to our knowledge have been conducted under free-ranging conditions and inclusive of infants. The main goal of this study was to establish feasibility of quantifying CSF oxytocin levels in free-ranging adult female and infant rhesus monkeys living on Cayo Santiago, PR. CSF oxytocin levels were examined in relation to individuals' demographic and reproductive characteristics as well as plasma cortisol levels. CSF oxytocin concentrations ranged from 36.02 to 134.41 pg/ml in adult females (ages 7-26 years; N = 31) and 35.94 to 77.3 pg/ml in infants (ages 38-134 days; N = 17). CSF oxytocin levels were positively correlated with adult female age and negatively correlated with infant age. The former correlation was driven by reproductive status. CSF oxytocin levels were unrelated to dominance rank or plasma cortisol levels. In contrast to a previous study of plasma oxytocin concentrations in this population, CSF oxytocin levels did not differ significantly between lactating and non-lactating females. These findings: 1) provide feasibility data for examining CSF oxytocin levels in free-ranging non-human primates and 2) indicate that CSF oxytocin levels may be a biomarker of age-related central nervous system changes across lifespan development. Research is now required to examine CSF oxytocin levels in the context of social functioning in free-ranging rhesus monkeys.

    View details for DOI 10.1037/a0019576

    View details for Web of Science ID 000278466000015

    View details for PubMedID 20528088

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