Abstract # 15:

Scheduled for Thursday, June 19, 2008 10:30 AM-10:40 AM: Session 2 (Meeting Room 1GHI) Oral Presentation


M. L. Schwandt1, S. G. Lindell1, C. Lindell2, J. D. Higley3, S. J. Suomi2, M. Heilig1 and C. S. Barr1
1National Institutes of Health/NIAAA-LCTS, NIH Animal Center, P.O. Box 529, Poolesville, MD 20837, USA, 2National Institutes of Health/NICHD, 3Department of Psychology, Brigham Young University
     The endogenous opioid system modulates hypothalamic-pituitary-adrenal (HPA) axis function and may influence both lactation and mother-infant attachment. In humans, a functional OPRM1 gene variant (OPRM1 A118G) is associated with attenuated HPA axis responses to stress. A functionally similar variant (OPRM1 C77G) in rhesus macaques has been associated with decreased basal cortisol levels. In this study, we tested whether rhesus macaque OPRM1 genotype influences HPA axis function in mothers during the postnatal period. Blood samples were collected from 58 primiparous and 75 multiparous mothers at postnatal days 7, 14, 21, 30, 60, 90, 120, and 150. Subjects were genotyped, and the effects of OPRM1 genotype and rearing condition (mother-reared, nursery-reared) on plasma adrenocorticotropic hormone (ACTH) and cortisol levels were analyzed using repeated measures ANOVA. There was a main effect of genotype on cortisol in both primiparous [F(1,56)=4.61; p=0.036] and multiparous mothers [F(1,73)=11.69; p=0.001]. In both groups, carriers of the C77G allele had lower cortisol levels [Tukey-Kramer, a=0.05]. There was a rearing by genotype interaction for ACTH in multiparous mothers [F(1,56)=5.17; p=0.03], such that mother-reared individuals with the C77G allele had lower ACTH levels compared to all other groups [Tukey-Kramer, a=0.05]. These results suggest that OPRM1 genotype influences HPA axis function during motherhood. Such findings imply that OPRM1 variation may underlie differences in post-partum changes in behavior in addition to the development of the mother-infant bond.