Effects of paced coital stimulation on estrus duration in intact cycling rats and ovariectomized and ovariectomized-adrenalectomized hormone-primed rats.

Feminine sexual behavior was examined in intact cycling rats and ovariectomized and ovariectomized-adrenalectomized hormone-primed rats with the use of a partitioned test cage in which the female controlled the timing of sexual contacts with males. Females received 9 or 10 intromissions in the partitioned test cage (paced) or with the partition removed (nonpaced) or received solitary exposure to the test cage or to mounts without intromission with the use of vaginal masks. Intact cycling (Experiment 1) and gonadectomized hormone-primed (Experiment 2) rats displayed similar patterns of contact with males: Exists from and latencies to return to the male compartment increased as the intensity of the antecedent coital stimulation increased (ejaculations greater than intromissions greater than mounts). Cycling females given experience with paced or nonpaced mating on the evening of proestrus did not exhibit differences in pacing behavior on a second test 17-24 days later. Those receiving paced coital stimulation showed a shorter duration of estrus than did those receiving nonpaced stimulation. Ovariectomized and ovariectomized-adrenalectomized paced rats given three successive doses of estradiol benzoate in combination with progesterone did not show shorter periods of estrus than nonpaced or mounts-only rats. These results suggest that ovarian output in response to paced cervical-vaginal stimulation may contribute to the termination of estrus in the rat.