Relevance of mating-associated stimuli, ovulation, and the progesterone receptor for the post-coital inhibition of estrous behavior in the female rabbit

Abstract

Estrous female domestic rabbits (Oryctolagus cuniculus) display scent marking ("chinning") and sexual receptivity. Mating induces ovulation, which occurs approximately 12h later, and also decreases chinning and receptivity. In the present study, we explored the participation of mating-associated stimuli, ovulation, and the progesterone receptor (PR) in mediating such behavioral effects. We found that copulatory stimuli were not necessary, and that ovulation alone was sufficient, as these behavioral changes were replicated in unmated females by intravenous administration of human chorionic gonadotropin (hCG). The post-mating administration (s.c.) of 5μg/day estradiol benzoate (EB), prevented the decline in chinning and receptivity. A lower dose of EB (1μg/day) had no effect, nor did the antiprogestin RU486 (20mg, s.c., administered 3h before mating). However, the combination of a single pre-mating administration of RU486 plus the post-mating administration of 1μg/day EB completely blocked the decline in estrous behavior. We propose that PR activation around the time of mating and a post-mating decline in ovarian estradiol secretion and/or estradiol responsiveness act in parallel to terminate estrus in this species.