Reiser G, Miledi R
Department of Biophysics, University College London, Great Britain.
Pflugers Arch. 1988 Jul;412(1-2):22-8. doi: 10.1007/BF00583727.
End-plates in denervated frog sartorius muscles were investigated, under voltage clamp, to determine the characteristics of miniature endplate currents (mepc) caused by the release of acetylcholine (ACh)-quanta from Schwann-cells. Staining for acetylcholinesterase ascertained that in most cases Schwann-cell mepc had been recorded focally from the end-plate. The mean amplitude of Schwann-cell mepc (about 1 nA) was smaller than the amplitude (3-4nA) of normal nerve evoked mepc. The amplitude distribution of Schwann-cell mepc was skewed, as were also the distributions of decay time constants and of rise times. Some Schwann-cell mepc appeared to be of composite nature, as shown by an inflexion on either the rising of falling phase. The decay time constant tau of both fast and slowly decaying Schwann-cell mepc increased with membrane hyperpolarization suggesting an exponential correlation. The potential dependence was 118 +/- 37 mV (means +/- SD from 6 experiments) for an e-fold change of tau, which does not differ significantly from that for neural mepc (98 mV). The cholinesterase inhibitor neostigmine increased the amplitude and prolonged the time course of Schwann-cell mepc to a similar degree after short and long term denervation, which indicates that cholinesterase was still functional after 3-4 months of denervation. The results show that the characteristics of Schwann-cell mepc resemble in many respects those of neural mepc but are more variable in shape and amplitude.
在电压钳制条件下，对去神经支配的青蛙缝匠肌终板进行了研究，以确定雪旺细胞释放乙酰胆碱（ACh）量子所引起的微小终板电流（mepc）的特征。乙酰胆碱酯酶染色确定，在大多数情况下，雪旺细胞mepc是从终板局部记录到的。雪旺细胞mepc的平均幅度（约1 nA）小于正常神经诱发的mepc幅度（3 - 4 nA）。雪旺细胞mepc的幅度分布呈偏态，衰减时间常数和上升时间的分布也是如此。一些雪旺细胞mepc似乎具有复合性质，表现为上升或下降阶段的拐点。快速和缓慢衰减的雪旺细胞mepc的衰减时间常数tau均随膜超极化而增加，表明存在指数相关性。tau的e倍变化的电位依赖性为118±37 mV（6次实验的平均值±标准差），与神经mepc的电位依赖性（98 mV）无显著差异。胆碱酯酶抑制剂新斯的明在短期和长期去神经支配后，对雪旺细胞mepc的幅度增加和时间进程延长的程度相似，这表明在去神经支配3 - 4个月后胆碱酯酶仍有功能。结果表明，雪旺细胞mepc的特征在许多方面与神经mepc相似，但形状和幅度更具变异性。
