Lim N F, Nowycky M C, Bookman R J
Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia 19104.
Nature. 1990 Mar 29;344(6265):449-51. doi: 10.1038/344449a0.
The release of neurohormone is widely thought to be exocytotic, involving Ca2(+)-dependent fusion of secretory vesicles with the plasma membrane. The inaccessibility of most nerve ending has so far hampered direct time-resolved measurements of neuronal exocytosis in response to brief depolarization. By using 'whole-terminal' patch-clamp and circuit-analysis techniques to measure membrane capacitance, we have now monitored changes in the surface membrane area of individual nerve terminals isolated from the mammalian neurohypophysis. A single depolarizing pulse leading to Ca2+ entry through voltage-gated calcium channels, rapidly and reproducibly increases the membrane area by an amount corresponding to the fusion of 1-100 secretory vesicles. The magnitude of the capacitance increase depends not only on Ca2+ entry and buffering, but also on the pattern of stimulation revealing facilitation, fatigue and recovery of the release process.
人们普遍认为神经激素的释放是通过胞吐作用实现的，这涉及分泌囊泡与质膜的Ca2(+)依赖性融合。由于大多数神经末梢难以接近，迄今为止，阻碍了对神经元在短暂去极化反应中胞吐作用进行直接的时间分辨测量。通过使用“全末梢”膜片钳和电路分析技术来测量膜电容，我们现在已经监测了从哺乳动物神经垂体分离出的单个神经末梢表面膜面积的变化。单个去极化脉冲通过电压门控钙通道导致Ca2+内流，迅速且可重复地使膜面积增加，增加的量相当于1 - 100个分泌囊泡的融合。电容增加的幅度不仅取决于Ca2+内流和缓冲，还取决于刺激模式，揭示了释放过程的易化、疲劳和恢复。
