Licht P, McCreery B R, Barnes R
Gen Comp Endocrinol. 1983 Jul;51(1):148-53. doi: 10.1016/0016-6480(83)90107-7.
Freshly captured female bullfrogs (Rana catesbeiana) were challenged with a standard dose (2 micrograms) of gonadotropin-releasing hormone (GnRH) shortly before and at the onset of the spawning season (in early April and mid-May) to examine the relationship between pituitary responsiveness and ovarian stage; males were also tested in April. As shown previously, increments in plasma gonadotropins induced by GnRH were consistently lower in females than in males. There was little difference in average responsiveness between the two collections of females and results for these were similar to those obtained at other times of the year. A wide range of ovarian stages was represented at both collection times as evidence by plasma steroid profiles, but there was no correlation between the GnRH-induced increments in plasma FSH and LH and plasma levels of androgens (testosterone and 5 alpha-dihydrotestosterone), estradiol-17 beta, or progesterone in the 71 females tested. Thus, there is no evidence of a feedback effect of ovarian steroids on the pituitary responsiveness to acute GnRH stimulation in the frog as has been demonstrated in mammals.
在产卵季节开始前及刚开始时（4月初和5月中旬），对刚捕获的雌性牛蛙（北美牛蛙）用标准剂量（2微克）的促性腺激素释放激素（GnRH）进行刺激，以研究垂体反应性与卵巢阶段之间的关系；4月也对雄性牛蛙进行了测试。如先前所示，GnRH诱导的血浆促性腺激素增加量在雌性中始终低于雄性。两组雌性的平均反应性差异不大，其结果与一年中其他时间获得的结果相似。通过血浆类固醇谱证明，两个采集时间点均代表了广泛的卵巢阶段，但在71只受试雌性中，GnRH诱导的血浆促卵泡激素（FSH）和促黄体生成素（LH）增加量与雄激素（睾酮和5α - 双氢睾酮）、雌二醇 - 17β或孕酮的血浆水平之间没有相关性。因此，没有证据表明青蛙的卵巢类固醇对垂体对急性GnRH刺激的反应性有反馈作用，而这在哺乳动物中已得到证实。
