Light Microscopic Evidence for Exocytosis in Nerve Terminals

关于递质是如何从神经末梢释放的问题上存在很大争议。两种假说，胞吐假说和双分泌假说，都有优缺点。这个项目的目的是确定哪一种假设是有用的。采用视频增强差示干涉显微镜对酶法分离的大鼠神经垂体神经末梢和培养的嗜铬细胞神经末梢进行了观察。电刺激引起的生理反应在监视器屏幕上直接观察到，放大倍数为12,000。许多0.2-0.5YTm的颗粒以布朗方式缓慢波动。在电刺激下，一些颗粒在光强度上突然变化，就像它们在两种类型的制剂中一个接一个地弹出一样。同样的反应也可以通过应用富钾溶液来诱导。这张弹出的图像与唾液腺、杯状细胞、垂体前叶细胞、一些嗜铬细胞和其他分泌细胞在刺激下发现的完全相似。通过去除介质中的钙离子，可以完全和可逆地抑制爆裂反应。重复刺激对爆裂反应有易化作用。这些发现清楚地表明，神经末梢能够通过胞吐过程释放递质。我非常相信，这场历史争议现在终于得到了解决。

It was very controversial over the question how the transmitters are released from the nerve terminals. Two hypotheses, the exocytosis hypothesis and the diacrine hypothesis, both had advantages and disadvantages. The purpose of this project was to determine which hypothesis is instrumental. I employed video-enhanced differential interference microscope to observe the nerve terminals enzymatically isolated from neurohypophysis of the rat and the nerve terminals of cultured chromaffin cells. Their physiological responses induced by electrical stimulation were directly observed in monitor screen at a magnification of X12, 000. Many granules of 0.2 - 0.5 ytm were seen to be fluctuating slowly in a Brownian fashion. Upon electrical stimulation, some granules abruptly changed in light intensity as if they popped one after another in both types of preparation. The same response could be induced also by application of a K-rich solution. This popping image was exactly similar to those found in salivary glands, goblet cells, anterior pituitary cells, some of chromaffin cells, and other secretory cells upon their stimulation. The popping response could be suppressed completely and reversibly by removal of Ca ions from the medium. Repetitive stimulation had facilitatory effects on the popping responses. These findings clearly indicate that nerve terminals are capable of releasing transmitters by the process of exocytosis. I am very convinced that the historical controversy has now been finally settled.