Stanley E F, Drachman D B
Brain Res. 1983 Feb 14;261(1):172-5. doi: 10.1016/0006-8993(83)91300-8.
Botulinum (BOT) toxin is known to block quantal acetylcholine (ACh) release at the neuromuscular junction but little is known about its effect on non-quantal ACh release. We have examined the effect of BOT on non-quantal ACh release directly using a variant of the electrophysiological technique described by Katz and Miledi. This method is based on the observation that non-quantally released ACh results in a small, continual depolarization of the postsynaptic membrane, after inhibition of cholinesterase. This depolarization can be revealed by suddenly blocking ACh receptors with a pulse of curare, resulting in an abrupt hyperpolarization, the amplitude of which is presumed to be proportional to the rate of non-quantal ACh release. BOT treatment resulted in a marked decrease in quantal ACh release as shown by miniature endplate potential (m.e.p.p.) frequencies (control 0.65 +/- 0.33 m.e.p.p.s/s; BOT 0.03 +/- 0.03 m.e.p.p.s/s). However, non-quantal ACh release measured by the curare induced hyperpolarization, was not significantly different in control and BOT treated diaphragms (control 1.01 +/- 0.09 mV: BOT 1.03 +/- 0.11 mV). Our results show that BOT does not block non-quantal ACh release at a time when it has a profound effect on spontaneous quantal ACh release. This suggests that quantal and non-quantal ACh release take place through different release mechanisms.
已知肉毒杆菌（BOT）毒素可阻断神经肌肉接头处的量子化乙酰胆碱（ACh）释放，但对其对非量子化ACh释放的影响知之甚少。我们直接使用Katz和Miledi描述的电生理技术变体，研究了BOT对非量子化ACh释放的影响。该方法基于以下观察结果：在抑制胆碱酯酶后，非量子化释放的ACh会导致突触后膜出现微小的持续去极化。通过用箭毒脉冲突然阻断ACh受体可以揭示这种去极化，从而导致突然的超极化，其幅度被认为与非量子化ACh释放速率成正比。BOT处理导致量子化ACh释放显著减少，如微小终板电位（m.e.p.p.）频率所示（对照0.65±0.33个m.e.p.p.s/s；BOT 0.03±0.03个m.e.p.p.s/s）。然而，通过箭毒诱导的超极化测量的非量子化ACh释放在对照和BOT处理的膈肌中没有显著差异（对照1.01±0.09 mV：BOT 1.03±0.11 mV）。我们的结果表明，在BOT对自发量子化ACh释放有深远影响时，它不会阻断非量子化ACh释放。这表明量子化和非量子化ACh释放通过不同的释放机制发生。
