Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington, Kentucky 40536-0084, USA.
J Neuroendocrinol. 1992 Jun;4(3):311-7. doi: 10.1111/j.1365-2826.1992.tb00173.x.
Gonadotropin secretion from the pituitary is regulated in large part by steroid action on the brain. An important question concerns whether luteinizing hormone-releasing hormone (LHRH) neurons themselves transduce steroid signals, or whether, alternatively, steroid-sensitive interneuronal populations regulate their activity. A previous study in the rat employing steroid autoradiography combined with LHRH immunocytochemistry revealed that only an exceedingly small percentage of LHRH-immunoreactive (ir) neurons was estrogen concentrating. This study has examined the relationship of estrogen receptive and LHRH-ir cells in the male and female guinea-pig brain with double label immunocytochemistry. Since estrogen receptor-ir, as demonstrated with antibody H222, is known to be confined predominantly to the cell nucleus, whereas LHRH-ir is localized mainly in the cytoplasm, single cells can be double-labeled. Diaminobenzidine tetrahydrochloride was used for localization of LHRH-ir while nickel-enhanced diaminobenzidine tetrahydrochloride was used for localization of estrogen receptor-ir. The results revealed that there were many brain nuclei that contained both LHRH and estrogen receptor-positive cells, including the preventricular periventricular nucleus, the anterior subcompact nucleus of the medial preoptic nucleus (MPNa), the remainder of the medial preoptic nucleus, the retrochiasmatic area, and the anterior, dorsomedial, ventrolateral and arcuate nuclei. However, of a total of 2,604 LHRH-ir cells that were examined, we observed only 5 double-labeled cells (<0.2%). The double-labeled cells were not restricted to a single nucleus; they were present in the MPNa, the retrochiasmatic area and the arcuate nucleus. Moreover, at the light microscopic level, LHRH cells quite frequently appeared to be apposed to estrogen receptor-positive cells (8.8% in the female), especially in the MPNa. These results lend further support to the notion that estrogen-mediated regulation of the LHRH system is achieved primarily through estrogen receptive interneurons. However, due to the existence of LHRH-LHRH synaptic interactions, the possibility also exists that a small population of estrogen-sensitive LHRH neurons could contribute to generalized activation of the LHRH system.
垂体促性腺激素的分泌在很大程度上受到类固醇对大脑的作用的调节。一个重要的问题是黄体生成素释放激素 (LHRH) 神经元本身是否传递类固醇信号，或者相反，类固醇敏感的中间神经元群体是否调节它们的活性。以前在大鼠中进行的一项研究采用类固醇放射自显影技术结合 LHRH 免疫细胞化学显示，只有极少数的 LHRH-免疫反应性 (ir) 神经元聚集雌激素。这项研究检查了雄性和雌性豚鼠脑中的雌激素受体和 LHRH-ir 细胞之间的关系，方法是采用双标记免疫细胞化学。由于众所周知，雌激素受体-ir（如抗体 H222 所示）主要局限于细胞核，而 LHRH-ir 主要定位于细胞质，因此可以对单个细胞进行双标记。二氨基联苯胺四盐酸盐用于定位 LHRH-ir，而镍增强的二氨基联苯胺四盐酸盐用于定位雌激素受体-ir。结果表明，有许多包含 LHRH 和雌激素受体阳性细胞的脑核，包括室前室旁核、视前正中核的前亚致密核 (MPNa)、前正中核的其余部分、视交叉后区以及前、背内侧、腹外侧和弓状核。然而，在总共检查的 2604 个 LHRH-ir 细胞中，我们只观察到 5 个双标记细胞（<0.2%）。双标记细胞不限于单个核；它们存在于 MPNa、视交叉后区和弓状核中。此外，在光镜水平，LHRH 细胞经常与雌激素受体阳性细胞（在女性中为 8.8%）相邻，特别是在 MPNa 中。这些结果进一步支持这样的观点，即雌激素介导的 LHRH 系统的调节主要通过雌激素受体中间神经元来实现。然而，由于存在 LHRH-LHRH 突触相互作用，也有可能一小部分雌激素敏感的 LHRH 神经元可能有助于 LHRH 系统的普遍激活。
