Adrenal suppression and sexual initiation in group-living female rhesus monkeys

Eight female rhesus monkeys living in an outdoor social group were studied for two menstrual cycles during the breeding season. During one cycle, adrenal steroids were suppressed for an average of 24 days using dexamethasone (0.6 mg/day) administered via subcutaneous osmotic minipumps. During the other cycle females were implanted with control pumps containing sterile water. Observers were blind to the treatments and treatment order was counterbalanced. Female sexual behavior was observed daily with each of two adult rhesus males. During dexamethasone treatment, cortisol levels were suppressed to less than 10% of control levels, and testosterone and androstenedione levels were suppressed to less than 50% of control, suggesting nearly total elimination of adrenal contribution to circulating androgen. All females showed hormonal evidence of ovulation. Adrenal suppression had no significant effect on female behavior, including approaches to the male and sexual solicits. In addition, no differences in any male behavior, including number of ejaculations, were seen between the two treatments. The continued cyclic copulation during adrenal suppression demonstrates that ovarian hormones are sufficient to modulate female rhesus sexual behavior and that adrenal androgens have little effect on the sexual behavior of intact, group-living rhesus females.