Abstract # 78:

Scheduled for Thursday, June 21, 2007 05:00 PM-07:00 PM: Session 7 (South Main Hall) Poster Presentation

Early Rearing Experience and Hypothalamic Pituitary Adrenal (HPA) Activity in Infant Rhesus Monkeys (Macaca mulatta) After a Separation Challenge

A. M. Dettmer1, A. M. Ruggiero2, M. D. Davenport3, M. A. Novak1,3, J. S. Meyer1 and S. J. Suomi2
1Neuroscience and Behavior Program, University of Massachusetts Amherst, Amherst, MA, USA, 2Laboratory of Comparative Ethology, NICHD/NIH, Poolesville, MD, USA, 3Division of Behavioral Biology, New England Primate Research Center, Harvard Medical School, Southborough, MA, USA
     Nursery rearing of macaques takes one of two forms, peer-rearing (PR) or surrogate-peer-rearing (SPR). Evidence suggests that SPR is superior to PR in terms of yielding normal behavior and eliminating excessive fearfulness. Furthermore, SPR monkeys are more likely than PR monkeys to interact with mother-peer-reared monkeys (MPR). We examined HPA activity using hair cortisol as a chronic measure and salivary cortisol as a point measure of the effects of a brief stressor. Twenty-four infants divided equally across rearing conditions (MPR, PR, and SPR) had their hair shaved at postnatal day 14 and again at 6 months. At 6 months of age, the animals were also exposed to a separation challenge wherein saliva samples were collected prior to and after the test. The 6 month hair and saliva samples were analyzed for cortisol using an enzyme immunoassay. Both MR and SPR infants exhibited significant increases in salivary cortisol in response to the separation challenge [t(7)=-2.99 and t(7)=-2.61, respectively; p<0.05] whereas PR infants did not. This difference appeared to be due to elevated basal cortisol levels in PR infants. Further support for the elevation in basal levels came from our preliminary findings of higher hair cortisol levels in PR monkeys. These results demonstrate that SPR infants show greater behavioral and physiological similarities to MPR infants than PR infants, thereby providing additional evidence of the superiority of the SPR rearing strategy.