Abstract # 4302 Event # 125:

Scheduled for Friday, June 22, 2012 04:00 PM-04:15 PM: Session 20 (Camellia ) Oral Presentation


THE EFFECTS OF BIRTH TIMING AND TEMPERATURE ON THE HPA AXIS IN 3-4 MONTH OLD RHESUS MONKEYS (MACACA MULATTA)

J. J. Vandeleest1, S. A. Blozis2, S. P. Mendoza1,2 and J. P. Capitanio1,2
1California National Primate Research Center, One Shields Avenue, Davis, CA 95616, USA, 2Department of Psychology, University of California, Davis
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     Our previous work has suggested that birth timing, the relative timing of births within a single birth season, may influence the activity of the HPA axis, likely through its impact on the mother-infant relationship. However, as cortisol is a metabolic hormone involved in thermoregulation, seasonal variation in ambient temperature during early postnatal development may also influence HPA axis activity. The current study examines the relative influences of birth timing and overnight ambient temperatures on HPA axis activity and regulation in 3-4 month old rhesus monkeys (N=338). Subjects were part of a biobehavioral assessment in which infants were separated from their mothers and relocated to a novel testing environment for 25-hours. Four blood samples were collected and assayed for cortisol concentrations and reflected HPA response to 1) 2 hr separation and relocation, 2) sustained challenge, 3) dexamethasone suppression, and 4) ACTH challenge. Nonlinear mixed modeling was used to examine how birth timing and ambient temperature impacted HPA axis activity and regulation (alpha=0.05). Results indicated that birth timing and ambient temperature both had significant, but opposing, effects on afternoon cortisol levels. Late born infants exhibited higher cortisol concentrations than did early born infants whereas low ambient temperatures were associated with higher cortisol levels. These results suggest that the effect of birth timing on the activity of the HPA axis may be due to multiple, potentially opposing factors.