ESTROGEN FACILITATION OF RELEASE OF PITUITARY OVULATING HORMONE IN THE RABBIT IN RESPONSE TO VAGINAL STIMULATION1

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Abstract
Although naturally estrous rabbits ordinarily ovulate following coital stimulation, very few respond in this manner to simple mechanical stimulation of the vagina. In this regard, among others, they differ from the estrous cat which readily ovulates in response to glass-rod stimulation of the vagina. The present study reveals that priming the estrous rabbit with moderate dosages of estrogen for two days or the anestrous rabbit for a longer period sets the stage for relase of pituitary ovulating hormone in response to artificial stimulation of the vagina in 40-459% of the cases. The ovarian follicles, ruptured in this response, become functional corpora lutea as evidenced by the decidual reaction to uterine trauma. The ovulatory response could not be evoked in pseudopregnant rabbits by these means. The response was blocked in estrous estrogen-treated rabbits by pentobarbital, atropine, dibenamine and reserpine. The report emphasizes the facilitatory function of estrogen in reflexo-genous ovulation and discusses its possible sites of action rather than supporting a very important role for vaginal stimulation among the afferent mechanisms triggered at coitus.