Effects of estrus, estrogen-progesterone priming, and vaginal stimulation on tonic immobility, dorsal immobility, and lordosis in the female rat.

Three complex inhibitory responses, tonic immobility, the dorsal immobility response, and lordosis, were studied in the intact female rat during estrus and diestrus and in ovariectomized rats with estrogen-progesterone treatment or controls. In each condition, the effects of vaginal-cervical stimulation were also studied. The results of two experiments indicate that estrus and estrogen-progesterone treatment significantly potentiate lordosis and the dorsal immobility response with or without vaginal-cervical stimulation. Tonic immobility was also potentiated by estrus and estrogen-progesterone treatment, but only if vaginal-cervical stimulation was applied. Vaginal-cervical stimulation potentiated both tonic immobility and the dorsal immobility response, but not lordosis, which was already at a high level.