Responses to copulatory stimulation in neonatally androgenized female rats

A series of experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female rats. The age at which animals began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized animals exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. The extent to which copulatory stimulation modified receptivity varied with the dose of TP injected neonatally and the condition of testing. Animals injected with high doses of TP (500 microgram) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions animals receiving 50 micrograms of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included one to five ejaculations, only control animals were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, animals that had neonatally received .5 microgram of TP, but not higher doses, did become pregnant. It is concluded that the capacity of systems mediating reproductive physiology and behavior to be facilitated by stimuli associated with males and that mating is a characteristic of the female rat which can be manipulated by injection of hormones during the neonatal period.