HYPOTHALAMIC REGULATION OF FEMALE SEXUAL BEHAVIOUR; ESTABLISHMENT OF BEHAVIOURAL OESTRUS IN SPAYED GUINEA-PIGS FOLLOWING HYPOTHALAMIC LESIONS

Abstract

Individual characteristics of sexual behaviour were empirically determined for twenty-seven spayed female guinea-pigs given three standardized tests after injection with 0.0034 mg of estradiol benzoate and, 36 hours later, 0.4 mg of progesterone. Following this preoperative series of tests, hypo-thalamic lesions were produced electrolytically at different loci with various parameters of current duration and intensity. Alterations in the patterns of sexual behavior displayed on three postoperative tests with identical hormonal treatments were evaluated statistically for each individual. Posteroventral hypothalamic lesions involving mammillary and premammillary structures were not associated with significant behavioral changes (N equals 4). Mid-ventral lesions were associated with alterations in response patterns in all but two animals. The behavioral changes were not correlated with size of lesions. Nine females with complete behavioral losses failed to display any signs of receptivity postoperatively. Ten showed statistically significant but incomplete losses in one or more of the components comprising the pattern of sexual behavior, and two females displayed behavioral estrus postoperatively in the absence of exogenous hormone. Lesions in females with behavioral estrus appear to be more anterior and possibly more medial than those which eliminate sexual behavior. Uteri of behavioral-estrous females were atrophic suggesting that no estrogen was provided by endogenous sources. The results suggest that mechanisms for both the facilitation and inhibition of female sexual behavior exist within the hypothalamus. Moreover, hypothalamic regulation of reproductive behavior is quantitative in nature, not "all-or-none", and a range of partial deficits in behaviour can be observed after hypothalamic damage.