Plasma cortisol responses to stress in lactating and nonlactating female rhesus macaques

• Type of Material: Article
• Authors: Dario Maestripieri, Emory University; Christy L. Hoffman, University of Chicago; Richelle Fulks, Emory University; Melissa S. Gerald, University of Puerto Rico
• Language: English
• Date: 2008-01
• Publisher: Elsevier: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2007 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.yhbeh.2007.09.013
• Title of Journal or Parent Work: Hormones and Behavior
• ISSN: 0018-506X
• Volume: 53
• Issue: 1
• Start Page: 170
• End Page: 176
• Grant/Funding Information: This research was supported by a grant from the Brain Research Foundation to D.M., NIH-NCRR grant CM-5-P40RR003640 to the Caribbean Primate Research Center, and NIH-NCRR grant RR-00165 to the Yerkes National Primate Research Center.
• Research Categories: Biology, Animal Physiology; Health Sciences, Human Development

Abstract

Lactating female rats without their pups exhibit lower HPA responsiveness to stress than nonlactating females. However, responsiveness to stress is similar when lactating females are tested with their pups and the stressor involves a potential threat to the offspring. This study constitutes the first comparison of stress responsiveness in lactating and nonlactating female nonhuman primates. Subjects were 53 multiparous female free-ranging rhesus macaques. Approximately half of the females were lactating and half were nonpregnant/nonlactating. Blood samples were obtained after capture and after overnight housing in an individual cage. Lactating females were tested with their infants. Lactating females had significantly higher plasma cortisol levels than nonlactating females on both days. Having or not having an infant was also a better predictor of plasma cortisol levels among all females than their age, dominance rank, group of origin, time of day at which the sample was obtained, and time elapsed since beginning of the sampling procedure or since anesthesia. Plasma cortisol levels of lactating females were not significantly correlated with post-partum stage or with the cortisol levels of their infants. Capture, handling, and individual housing in a cage are powerful psychological stressors for free-ranging primates. We suggest that the higher plasma cortisol levels exhibited by lactating females reflect greater responsiveness to stress associated with perception of risks to infants. Hyporesponsiveness to stress may not be a general characteristic of lactation in all mammalian species, but a short-term effect of infant suckling that is most apparent with stressors unrelated to the offspring.