Social subordination impairs hypothalamic-pituitary-adrenal function in female rhesus monkeys

• Type of Material: Article
• Authors: Vasiliki J. Michopoulos, Emory University; Katherine M. Reding, Emory University; Mark Wilson, Emory University; Donna Toufexis, Emory University
• Language: English
• Date: 2012-09
• Publisher: Elsevier: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.yhbeh.2012.07.014
• Title of Journal or Parent Work: Hormones and Behavior
• ISSN: 0018-506X
• Volume: 62
• Issue: 4
• Start Page: 389
• End Page: 399
• Grant/Funding Information: The study was supported by NIH grants HD46501 (MW), MH081816 (DT) and RR00165, and F31 MH085445 (VM).
• Keywords: ACTH; psychosocial stress; cortisol; social subordination; dexamethasone; monkeys
• Research Categories: Psychology, General; Biology, Neuroscience; Psychology, Behavioral

Abstract

Linear dominance hierarchies organize and maintain stability in female rhesus macaque (Macaca mulatta) social groups regardless of group size. As a consequence of their low social status, subordinate females suffer from an array of adverse outcomes including reproductive compromise, impaired immune function, and poor cardiovascular health. However, data that differentiate limbic-hypothalamic-pituitary adrenal axis (LHPA) parameters between dominant from subordinate female monkeys are inconsistent, bringing into question whether social subordination alters the LHPA axis in female macaques. One difficulty in examining LHPA function in macaques may be the confounding effects of cycling ovarian steroids that are known to modulate LHPA activity. The current study used ovariectomized dominant and subordinate female rhesus monkeys to examine the effect that social subordination has on LHPA function by measuring morning and diurnal serum cortisol levels, dexamethasone (Dex) suppression of cortisol, metabolic clearance of Dex, and ACTH stimulation of adrenal cortisol release and cortisol response following exposure to acute social isolation. Compared to dominant females, subordinate females showed diminished morning peak cortisol secretion, weakened glucocorticoid negative feedback, and decreased adrenal cortisol response to an ACTH challenge as well as a restrained cortisol response following social isolation. However, the metabolism of Dex did not account for differences in Dex suppression between dominant and subordinate females. These results indicate that the ability to mount and limit glucocorticoid release is significantly reduced by psychosocial stress in female rhesus macaques, suggesting a hyporesponsive LHPA phenotype which resembles that observed in several human psychopathologies.