| Abstract: | Findings from 6 experiments show that when a large dose of progesterone was administered to ovariectomized Sprague-Dawley rats 24 hrs after a 2-μg injection of estradiol benzoate (EB), sexual receptivity was inhibited at 54 hrs (sequential inhibition). Larger doses of progesterone (1 mg) were required to inhibit the induction of sexual receptivity when tested at 54 hrs than were necessary to facilitate at 30 hrs. This inhibition was not due to copulatory stimuli from the 1st test, because inhibition occurred even when the 1st test was omitted. The inhibition was dose dependent on estradiol; increasing the EB priming dose offset the inhibition caused by 1 mg of progesterone. The results of an experiment that behaviorally dissociated the antiestrogenic action of progesterone from that of a synthetic antiestrogen, CI-628, are consistent with the notion that progesterone and synthetic antiestrogens inhibit the neural effects of estradiol by separate mechanisms of action. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
