Shaw F D, Morris J F
Nature. 1980 Sep 4;287(5777):56-8. doi: 10.1038/287056a0.
Neurosecretory nerve endings in the rat neurohypophysis release their hormones by exocytosis subsequent to an influx of calcium from the external medium. The nerve endings are characterized by the presence of neurosecretory granules, mitochondria, occasional vacuoles, and a population of microvesicles similar in appearance to spherical synaptic vesicles. The function of the microvesicles has, for a long time, been uncertain. In view of evidence that coated microvesicles isolated from cerebral cortex are capable of ATP-dependent calcium accumulation, a method has now been developed for the visualization of calcium in the neurohypophysis at the ultrastructural level. With this technique, calcium precipitates are consistently seen in the microvesicles, mitochondria and glial cell (pituicyte) nuclei. In addition, the pituicyte cytoplasm and perivascular space show a diffuse precipitate which can be removed by washing the tissue prior to fixation. The function of the microvesicles might therefore be to sequester calcium within the nerve endings.
大鼠神经垂体中的神经分泌神经末梢，在外部介质中的钙流入后，通过胞吐作用释放其激素。神经末梢的特征是存在神经分泌颗粒、线粒体、偶尔的液泡，以及一群外观与球形突触小泡相似的微泡。长期以来，微泡的功能一直不确定。鉴于有证据表明，从大脑皮层分离出的被膜微泡能够进行依赖ATP的钙积累，现在已经开发出一种在超微结构水平上观察神经垂体中钙的方法。用这种技术，在微泡、线粒体和神经胶质细胞（垂体细胞）核中始终能看到钙沉淀。此外，垂体细胞的细胞质和血管周围间隙显示出弥漫性沉淀，在固定前清洗组织可以去除这种沉淀。因此，微泡的功能可能是在神经末梢内隔离钙。
