大鼠垂体前叶GABA能神经纤维支配的电镜研究(英文)

近年来的研究表明哺乳动物的垂体前叶接受SP、CGRP等肽能神经支配。免疫电镜研究发现 ,在SP、CGRP阳性末梢中 ,除了含有阳性的大致密芯囊泡外 ,还含有大量的清亮小泡 ,提示经典递质的存在 ,其性质目前尚不清楚。GABA参与垂体前叶腺细胞分泌活动的调节 ,是可能的递质候选者之一。应用免疫组化技术发现 ,在大鼠垂体前叶两翼的外侧部及浅表部位 ,分布有GABA免疫阳性末梢。应用包埋前免疫电镜技术 ,发现 85%的GABA免疫阳性末梢与前叶腺细胞直接接触 ,由多到少依次为生长激素细胞、泌乳素细胞和促肾上腺皮质激素细胞 ,并且与上述细胞形成典型的突触结构。GABA免疫阳性末梢与生长激素细胞形成非对称型突触结构 ,与促肾上腺皮质激素细胞形成对称型突触结构 ,而与泌乳素细胞间则既有对称型突触结构 ,又有非对称型突触结构。GABA免疫阳性末梢极少与促性腺激素细胞接触。结果表明大鼠垂体前叶接受GABA能神经纤维的支配 ,GABA能末梢可直接调控垂体前叶腺细胞的分泌。大鼠垂体前叶GABA能纤维的来源则有待进一步研究

GAB Aergic innervation of the rat anterior pituitary: a preembedding immunoelectron microscopical study

Peptidergic nerve fibers have been found in the anterior pituitary (AP) of several mammals. Previous electron microscopic immunocytochemical studies showed that peptide containing nerve terminals with dense core vesicles also contain a large number of small clear vesicles (SCVs), the content of which is unknown. The present study was undertaken to resolve whether GABA, a neuroactive amino acid that has been implicated in neuroendocrine regulation, is a possible candidate. Preembedding immunohistochemistry was used. GABA immunoreactive (ir) nerve fibers were distributed in specific regions of AP of the rat, mainly in lateral and superficial parts and, rarely in central parts. In the EM, 85% of GABA ir nerve terminals were seen to contact gland cells, identified as somatotrope, lactotrope and corticotrope, in decreasing order of frequency. Gonadotropes were rarely contacted. GABA ir terminals made asymmetric synapses with somatotrope, symmetric synapses with corticotrope, and both asymmetric and symmetric synapses with lactotropes. The present findings indicate that the anterior pituitary of the rat receives a direct GABAergic innervation, and the presence of synapses between the GABA ir terminals and anterior pituitary gland cells suggests that these GABA ir terminals may regulate the secretion of the AP gland cells directly. The origin of these GABA ir nerve fibers remains to be identified.