Food-reinforced responding in rats during estrus.

Abstract

7 naive female Holtzman albino rats were food deprived and trained to press a lever for food on a schedule of reinforcement in which every 10th response was reinforced. Periodic response-rate decreases were observed on days of maximum vaginal cornification and disappeared following ovariectomy. Estradiol injection 20 hr. before the session produced a dose-related response-rate change in ovariectomized females, 25 MUg/kg producing a decrease similar to that associated with vaginal cornification. Since sexual receptivity and locomotor activity have not been reported 20 hr. after 25 MUg/kg of estradiol, the changes in food intake associated with maximum vaginal cornification appear to be the direct result of estrogen secretion and not secondary to heightened sexual motivation or increased activity. (15 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)