Social setting, social rank and HPA axis response in cynomolgus monkeys.
BACKGROUND
Hypothalamic-pituitary-adrenal (HPA) axis activity under different social settings in non-human primates is understudied.


OBJECTIVE
The aim of this study is to evaluate the response of pituitary-adrenal hormones (adrenocorticotropic hormone (ACTH) and cortisol) to pharmacological challenges of the HPA axis in male cynomolgus macaques under different social settings.


METHODS
Male cynomolgus macaques (Macaca fascicularis, n = 11) were individually (A) and socially housed (B) in alternation, over consecutive months, in an ABA design. During each experimental phase, plasma ACTH and cortisol were measured in response to low- and mild-intensity psychological stressors and following administration of saline, naloxone, ovine-corticotropin-releasing factor (oCRF), and dexamethasone.


RESULTS
These data demonstrate that cortisol measured under low stress conditions is sensitive to social rank (dominance hierarchy) and distinguishes dominant from non-dominant animals during both individual and social settings. Administration of naloxone resulted in elevated circulating ACTH and cortisol, while oCRF only increased circulating cortisol. During social housing, the cortisol response to naloxone and oCRF was increased, whereas dexamethasone suppression of ACTH and cortisol remained consistent across all social settings.


CONCLUSIONS
Circulating ACTH and cortisol are differentially sensitive to changes in social settings in non-human primates. Cortisol response increased during social housing and could be stimulated by both naloxone and oCRF, whereas ACTH response was generally not influenced by social setting or oCRF but was increased by naloxone. These data show differential adrenal and pituitary response to changes in social settings and a small, but consistent, effect of social dominance.
Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97202, USA.
Vanessa A
VA
Jimenez
Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97202, USA.
Daicia C
DC
Allen
Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97202, USA.
Megan N
MN
McClintick
Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97202, USA. grantka@ohsu.edu.|Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR, 97006, USA. grantka@ohsu.edu.
Kathleen A
KA
Grant
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism*; D007398:Interpersonal Relations; D008252:Macaca fascicularis; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000378:metabolism*; D012930:Social Dominance
D009270:Naloxone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
ACTH; Cortisol; HPA axis; Monkey; Social rank