Neuroendocrine mechanism of estrous behavior in the Shiba goat

哺乳动物发情行为的发生受内分泌的控制。排卵前卵泡的发育伴随着雌二醇分泌的增加，在大多数物种中，循环雌二醇水平的升高诱导了发情行为和排卵前LH的激增，尽管实际的发情行为模式在物种间存在较大差异。然而，引起发情和黄体生成素激增的中枢神经元机制尚不清楚。本研究采用电生理、免疫组织化学和生化等技术对柴山羊的促性腺激素释放激素神经元进行了多方面的研究。下丘脑十肽GNRH不仅调节垂体促性腺激素的分泌，还参与动情行为的表达。本研究包括以下四个主要课题。[1]山羊脑立体定向手术方法的发展。对GNRH脉冲发生器活性的更多研究。脑内GNRH神经元的免疫组织化学定位。[4]正中隆起处GNRH神经分泌的微透析分析。通过采用最新的神经生理学技术，我们能够监测清醒和不受约束山羊下丘脑GNRH神经元的神经分泌活动。主要发现如下：(1)大多数GNRH免疫反应细胞分布在视前区/间隔区，并通过两条主要途径向中位突起尾部投射它们的火焰；(2)下丘脑MUA截击评估的GNRH脉冲发生器活性在雌二醇诱导的黄体生成素激增期间继续降低脉冲频率；(3)微透析灌注液中GNRH水平在黄体生成素激增开始时急剧增加。综上所述，这些结果表明，通常与发情相关的黄体生成素激增是由GNRH激增引起的，而这种Gn*激增是由一种神经元机制控制的，这种机制本质上不同于调节促性腺激素分泌基础模式的GNRH脉冲发生器。少

Onset of estrous behavior is under the endocrine control in mammalian species. Development of preovulatory follicles is accompanied by increasing estradiol secretion, and the rise of circulating estradiol level induces the estrous behavior as well as the preovulatory LH surge in most species, despite considerable inter-species differences of actual behavioral pattern of estrus. The central neuronal mechanism eliciting both the estrous and the LH surge is, however, poorly understood.In the present study we studied about the gonadotropin-releasing hormone(GNRH)neuron in the Shiba goat from various aspects using electrophysiological, immunohistochemical and biochemical techniques. The hypothalamic decapeptide GNRH is not only regulating the pituitary gonadotropin secretion but also known to be involved in the expression of estrous behavior. The study consists of following four main subjects.[1]Developmentof the method for stereotaxic surgery of the goat brain.[2]Electrophysiological inves … More tigation of the GNRH pulse generator activity.[3]Immunohistochemical localization of GNRH neurons in the brain.[4]Microdialytic analysis of GNRH neurosecretion at the median eminence.By adopting the latest neurophysiological techniques we were able to monitor the neurosecretory activity of hypothalamic GNRH neurons in conscious and unrestrained goats. Major finding are as follows : (1)Majority of GNRH immunoreactive cells are distributed in the preoptic/septal area and project their fires caudally to the median eminence via two main pathways, (2)the GNRH pulse generator activity, as assessed by hypothalamic MUA volleys, continues with decreased pulse frequency during the LH surge induced by estradiol in ovariectomized goat, (3)GNRH levels in the microdialysis perfusate increase dramatically at the onset of LH surge. These results, taken together, suggest that the LH surge that is normally associated with the estrous is induced by the GNRH surge, and this Gn* surge is under the control of a neuronal mechanism that is intrinsically different from the GNRH pulse generator that regulates basal patterns of gonadotropin secretion. Less