The effect of dexamethasone, given either alone or together with testosterone propionate or androstenedione, was studied in nine female rhesus monkeys (paired with three males) by making quantitative observations on behaviour in the laboratory.
Dexamethasone (0·5 mg/kg/day) given to oestrogen-treated ovariectomized female monkeys made them sexually unreceptive, and there was an associated decline in the level of the male's mounting activity. Testosterone propionate (100 or 200 μg/day) reversed completely the effects of dexamethasone on sexual behaviour. Androstenedione (100, 200 or 400 μg/day) had similar, but less marked, effects whereas cortisol (10 mg/day) or progesterone (100, 200 or 500 μg/day) were ineffective. Treating a female with testosterone prevented dexamethasone from reducing sexual receptivity. Parallel determinations of urinary free cortisol showed that the dexamethasone had suppressed the secretory activity of the adrenal cortex. There were no consistent changes, under any treatment, in the females' vaginal epithelia, sexual skins or clitorides, or in their water or electrolyte metabolism.
These findings indicate that adrenal androgens regulate sexual receptivity in these female primates, probably by an action on the central nervous system.