Molgo J, Pecot-Dechavassine M
Laboratoire de Neurobiologie Cellulaire et Moléculaire du CNRS, Gif sur Yvette, France.
Neuroscience. 1988 Feb;24(2):695-708. doi: 10.1016/0306-4522(88)90362-4.
The quantal acetylcholine release and the ultrastructural effects of the metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone have been examined at frog neuromuscular junctions. Carbonyl cyanide m-chlorophenylhydrazone (2 microM) caused a temperature-dependent block of evoked quantal transmitter release accompanied by an increase in the rate of spontaneous quantal release. The carbonyl cyanide m-chlorophenylhydrazone-induced increase in miniature endplate potential frequency was neither antagonized nor prevented by tetrodotoxin. It also occurred in a Ca2+-free medium and after replacement of Ca2+ by Sr2+, indicating that it does not depend upon a Na+ or Ca2+ influx from the external medium but may act by releasing Ca2+ from intraterminal stores. Spontaneous quantal transmitter release was exhausted irreversibly within 4 h of carbonyl cyanide m-chlorophenylhydrazone (2 microM) action, during which time an average of 4.7 x 10(5) acetylcholine quanta were released per junction. The morphologic analysis revealed a significant temperature and time-dependent reduction in the number of synaptic vesicles with swelling and dispersion of mitochondria within the motor nerve terminals. Changes in synaptic vesicle number appear to be directly related to the intensity of transmitter release. The good correlation observed between the number of quanta secreted and the number of vesicles lost by nerve terminals in the absence of vesicle recycling provides an estimate of the initial store of transmitter quanta.
在青蛙神经肌肉接头处，对量子化乙酰胆碱释放以及代谢抑制剂间氯苯腙羰基氰化物的超微结构效应进行了研究。间氯苯腙羰基氰化物（2微摩尔）引起了温度依赖性的诱发量子化递质释放阻滞，并伴有自发量子化释放速率的增加。间氯苯腙羰基氰化物诱导的微小终板电位频率增加既未被河豚毒素拮抗也未被其阻止。它也发生在无钙培养基中以及用Sr2+替代Ca2+之后，这表明它不依赖于来自外部介质的Na+或Ca2+内流，而是可能通过从终末内储存库释放Ca2+来发挥作用。在间氯苯腙羰基氰化物（2微摩尔）作用的4小时内，自发量子化递质释放不可逆地耗尽，在此期间每个接头平均释放4.7×105个乙酰胆碱量子。形态学分析显示，运动神经末梢内突触小泡数量显著减少，且线粒体肿胀和分散，这种减少具有温度和时间依赖性。突触小泡数量的变化似乎与递质释放的强度直接相关。在没有小泡循环的情况下，观察到分泌的量子数量与神经末梢丢失的小泡数量之间具有良好的相关性，这为递质量子的初始储存量提供了一个估计值。
