Smith M J, Jiennes L, Wise P M
Department of Physiology, University of Kentucky College of Medicine, Lexington 40536-0298, USA.
Endocrinology. 2000 Nov;141(11):4317-20. doi: 10.1210/endo.141.11.7876.
In mammals, the timing and occurrence of the preovulatory LH surge critically depends on the proper functioning of the suprachiasmatic nucleus (SCN). Recent evidence suggests that vasoactive intestinal polypeptide (VIP) conveys time of day information from the SCN to GnRH neurons. However, it is not completely clear whether this action is exerted directly at the level of the GnRH neuron. To determine if GnRH neurons are direct targets for VIP, triple-label immunofluorescence was utilized to simultaneously localize GnRH, VIP and VIP2 receptor protein. The present results demonstrate that about 40% of all GnRH neurons analyzed contain VIP2 receptor immunoreactivity and that VIP-containing processes were seen in close apposition to a significant number of VIP2 receptor-positive GnRH neurons. GnRH neurons that exhibit immunoreactivity for the VIP2 receptor are located predominantly in the OVLT region and the rostral preoptic area. In the median eminence, where the majority of GnRH neurons terminate, VIP2 receptor immunoreactivity was absent. In summary, these findings indicate that VIP can communicate directly with GnRH neurons.
在哺乳动物中，排卵前促黄体生成素激增的时间和发生情况严重依赖于视交叉上核（SCN）的正常功能。最近的证据表明，血管活性肠肽（VIP）将一天中的时间信息从SCN传递给促性腺激素释放激素（GnRH）神经元。然而，这种作用是否直接在GnRH神经元水平发挥尚不完全清楚。为了确定GnRH神经元是否是VIP的直接靶点，采用三重标记免疫荧光法同时定位GnRH、VIP和VIP2受体蛋白。目前的结果表明，在所有分析的GnRH神经元中，约40%含有VIP2受体免疫反应性，并且在大量VIP2受体阳性的GnRH神经元附近可见含VIP的突起。表现出VIP2受体免疫反应性的GnRH神经元主要位于终板血管器区域和视前区嘴侧。在大多数GnRH神经元终止的正中隆起中，不存在VIP2受体免疫反应性。总之，这些发现表明VIP可以直接与GnRH神经元进行交流。
