Nature and Physiological significance of clear microvesicles in the neuroendocrine nerve endings

为阐明大鼠下丘脑-垂体系统神经分泌神经末梢内存在的透明微泡的性质及其生理意义，用免疫电镜技术观察了微泡内某些神经活性物质的超微结构定位。1.谷氨酸免疫反应性用包埋后免疫金染色法观察了谷氨酸免疫反应性的超微结构分布。在神经垂体，谷氨酸受体免疫反应性：N-甲基-D-天冬氨酸（NMDA）-RI受体免疫反应性：位于下丘脑室周神经末梢内的微囊泡;酪氨酸羟化酶（TH）免疫反应性：位于下丘脑室周神经末梢内的微囊泡。在下丘脑（A12，A14）含儿茶酚胺神经末梢内的微泡聚集区中发现突触素样免疫反应阳性。上述谷氨酸及其受体的超微结构定位结果提示，谷氨酸在神经分泌终末中通过自显影机制参与激素分泌。

To clarify the nature and physiological significance of the clear microvesicles within the neurosecretory nerve endings of the rat hypothalamo-hypophysial system, ultrastructural localization of some neuroactive substances in the microvesicles has been examined by immunoelectron microscopy.1.Glutamate immunoreactivityUltrastructural distribution of glutamate immunoreactivity was observed using the post-embedding immunogold staining method. In the neurohypophysis, glutamate immunoreactivity was found to be localized in the area where numerous microvesicles aggregate Many immunogold particles were observed in the interior of microvesicles.2.Glutamate receptor immunoreactivityImmunoparticles for N-methyl-D-Aspartate (NMDA)-RI receptor was localized to the microvesicles within the nerve endings in the periventricular uncles of the hypothalamus.3.Tyrosine hydroxylase (TH) immunoreactivityTH-like immunoreactivity was found in the aggregate area of microvesicles within the catecholamine-containing nerve endings of the hypothalamus (A12, A14).4.Synaptophysin immunoreactivity was found in the microvesicles within the neurosecretory endings of the neurohypophysis. The above findings of ultrastructural localizations of glutamate and its receptor suggest that glutamate play some important roles of hormone secretion in the neurosecretory endings through autorine mechanism.