Twelve non-virgin females were gonadectomized and tested for sexual behaviour 5, 10, 15 and 20 weeks after the operation. Most of the females showed considerable receptive behaviour during one or more tests with a general increase in receptivity from 5 to 10 weeks. Groups of non-virgin and virgin females were tested over a period of several days immediately following partial or total gonadectomy. Females gonadectomized on the 19th day of a 24 to 27-day gestation cycle showed practically no sexual behaviour over a 10-day period of testing. Females from which only the embryos were removed on day 19 performed normal amounts of receptive behaviour. Females with embryos removed at day 11 displayed very little receptive behaviour. Virgin females, receptive at first, showed a rapid decline in receptivity 6 days after total gonadectomy. An initial decline in sexual behaviour follows gonadectomy but several weeks later sexual behaviour reappears and females may respond fully to male displays. Thus the ovary is not essential for the occurrence of complete patterns of behaviour. On the other hand, the regular cycles in non-virgin females, the persistent responsiveness of virgin females and the initial decline in receptivity after gonadectomy all suggest that the ovary exerts a regulating and perhaps stimulating influence upon a more direct control, perhaps by the pituitary. Evidence for such a direct control is provided by the finding that hypophysectomy brings about an immediate cessation of sexual behaviour. Behavioural receptivity is not correlated with the presence of corpora lutea. Periods of maximum receptivity appear to be correlated with vitellogenesis in the ovary and hence presumably with the secretion of gonadotrophic hormone by the pituitary. Apart from its effects upon ovarian development, gonadotrophic hormone may also stimulate secretion of an ovarian hormone involved in the regulation of receptivity. The ovarian hormone may in its turn have a feedback effect upon the output of gonadotrophin or some other pituitary factor directly involved in the control of sexual receptivity. © 1968.
