Sexual behavior and some of its physiological consequences in persistently estrous aged female rats

Sexual behavior and some of its consequences were assessed in female rats which, with advancing age, had come to exhibit persistent vaginal estrus (PVE). Sexual receptivity, defined by the animal’s readiness to exhibit lordosis when mounted, was comparable across all ages evaluated. However, sexual proceptivity, defined by measures indicative of the female’s seeking mating opportunities, was determined to be much suppressed in 18 to 20 month old PVE females compared to either younger cyclic females or 12 to 15 month old PVE females. Mating disrupted the PVE pattern. The length of time animals remained out of estrus was positively correlated with the number of intromissions achieved by the male. However, pregnancy was not observed in any of the PVE females and examination of their ovaries and the responses of their uteri to traumatization provided no evidence of progestational responses in these animals. The behavioral data indicate that with continued exposure to the hormonal conditions of PVE there is a suppression of systems mediating the proceptive components of sexual behavior in female rats. It is suggested that changes in the concentrations of pituitary and/or ovarian hormones reported to occur as PVE rats continue to age may account for these changes in behavior.