New data concerning the control by the adrenals of sexual receptivity in the rat

The proportion of receptive females during the night from proestrus to estrus (mating frequency) was estimated in 4-day cyclic rats ovariectomized at different times of the day of proestrus. A sharp decrease in mating frequency occurred in females ovariectomized at 15:00-16:00 as compared with intact animals. A slighter, although significant decrease in mating frequency, was observed in females ovariectomized at 8:00-9:00 and 13:00-14:00. Sexual receptivity was only partially recovered following ovariectomy at 17:30-18:30. Chronic adrenalectomy completely prevented estrous receptivity in females ovariectomized at any time of proestrus as compared to adrenalectomized nonovariectomized females which displayed a normal estrous receptivity during the night from proestrus to estrus. A higher blood progesterone level was observed in receptive rats between 15:00 and 16:00 than in nonreceptive ones. The temporal relationships between the ovary and the adrenals in the control of estrous receptivity were discussed in the light of these observations.