| Summary: | The onset and termination of female rat sexual receptivity are regulated by the activation of steroid hormone receptors. In addition, the onset and termination of sexual receptivity are influenced by mating stimulation. For example, repeated mating stimulation increases sexual behavior in previously unreceptive estradiol-primed female rats. Apparently, sensory cues from the male rat lead to changes in female sexual behavior. The current studies investigated the exact sensory cues responsible for these changes and the mechanisms by which they influence sexual behavior. Mating-induced increases in sexual behavior appear to result largely from vaginal-cervical stimulation (VCS) received from intromissions and ejaculations. Furthermore, it is likely that the effects of VCS are mediated by ligand-independent activation of progestin receptors. Likewise, odors from male rats are necessary for maximal increases in sexual behavior following repeated mating; however, unlike VCS, odors do not seem to influence sexual behavior via a progestin receptor-dependent mechanism. Mating stimulation also accelerates estrous termination. The mechanisms mediating the acceleration of estrous termination following mating were also investigated. It has been hypothesized that mating-induced estrous abbreviation results from down-regulation of progestin receptors; however, several immunocytochemical studies found no evidence supporting this hypothesis. Instead, it appears that the effects of mating stimulation on estrous termination are more complex than previously appreciated. It appears that, while VCS decreases levels of sexual behavior, other sensory cues (e.g. flank stimulation and odors) maintain high levels of sexual receptivity. Thus, the results suggest that estrous duration is the result of a complex interplay between those factors that promote the expression of sexual receptivity and those that inhibit it.
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