Abstract # 23:

Scheduled for Thursday, June 19, 2008 03:50 PM-04:05 PM: Session 3 (Meeting Room 2DEF) Symposium

Effects of lactation on pituitary-adrenal responses to stress in laboratory-housed common marmosets (callithrix jacchus)

W. Saltzman1,2, C. A. Boettcher2, K. A. Crosno2 and D. H. Abbott2,3
1University of California, Department of Biology, Riverside, CA 92521, USA, 2National Primate Research Center, University of Wisconsin - Madison, 3Department of Obstetrics and Gynecology, University of Wisconsin - Madison
     In several mammalian species, lactating females exhibit blunted neural, endocrine, and behavioral responses to stressors, including diminished responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis. To our knowledge, however, lactational hyporesponsiveness has not been investigated systematically in nonhuman primates. Therefore, we compared HPA responses to standardized stressors in female common marmosets that either were (n=5) or were not lactating (n=6). Each marmoset underwent (1) a restraint stressor during the early follicular phase of the ovarian cycle (approximately 5 weeks postpartum) and (2) exposure to a simulated hawk predator during the early to mid-luteal phase (approximately 7 weeks postpartum). Lactating females were tested in the presence of one of their infants. Blood was collected before, during, and immediately after each test for determination of plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations. Lactating females tended to have lower afternoon ACTH but higher afternoon cortisol levels than non-lactating females, both at baseline and in response to stress. Consequently, cortisol-to-ACTH ratios were elevated in lactating females during the earlier lactational period [ANOVA, a=0.05], as compared to non-lactating females, but incremental responses to stress did not differ [ANOVA, a=0.05]. These findings suggest that the lactational period in common marmosets may be associated with enhanced adrenocortical responsiveness to ACTH and that this primate may differ from non-primate mammals in maintaining HPA reactivity to stress during lactation. Supported by NIH MH075973.