Buckley K M, Landis S C
J Neurocytol. 1983 Feb;12(1):93-116. doi: 10.1007/BF01148089.
The morphological correlates of transmitter release from synapses and varicosities were examined in mature cultures of sympathetic neurons dissociated from neonatal rat superior cervical ganglia. The number of synaptic vesicles decreased in synapses and varicosities depolarized with 53 mM K+. The decrease in vesicle number was accompanied by striking changes in the appearance of the synaptic terminals and an increase in their mean circumference. Coated pits and membrane-bound cisternae were observed more frequently in synapses and varicosities of depolarized neurons than in terminals of resting neurons. These morphological changes were not seen when the neurons were depolarized in the presence of Co2+, consistent with the Ca2+-dependence of transmitter release from these neurons. In freeze-fracture replicas of depolarized neurons, numerous dimples were observed in the cytoplasmic leaflet of synapses and varicosities, adjacent to large 12-14 nm particles. After a period of recovery in 5 mM K+ medium, the number of synaptic vesicles and the shape of synaptic terminals returned to normal. When horseradish peroxidase (HRP) was included in the medium as an extracellular tracer during depolarization and recovery, a significant proportion of small, synaptic vesicles contained reaction product. Label was also present in coated vesicles and cisternae. Neurons which were depolarized in medium containing Co2+ or were exposed to HRP without depolarization contained few labelled synaptic vesicles. The proportion of labelled vesicles was not significantly different in synapses and varicosities, nor did it vary consistently with the transmitter identity of the neurons. These observations are consistent with the hypothesis that transmitter release occurs from varicosities as well as from synapses of postganglionic sympathetic neurons by exocytosis of the small synaptic vesicles, and that at least some new vesicles are formed from the nerve terminal membrane.
在从新生大鼠颈上神经节分离出的交感神经元的成熟培养物中，研究了突触和曲张体中递质释放的形态学相关因素。用53 mM K⁺使突触和曲张体去极化后，突触小泡数量减少。小泡数量的减少伴随着突触终末外观的显著变化及其平均周长的增加。与静息神经元的终末相比，在去极化神经元的突触和曲张体中，包被小窝和膜结合池更频繁地被观察到。当神经元在Co²⁺存在的情况下去极化时，未观察到这些形态学变化，这与这些神经元递质释放对Ca²⁺的依赖性一致。在去极化神经元的冷冻蚀刻复制品中，在突触和曲张体的胞质小叶中观察到大量凹坑，与大的12 - 14 nm颗粒相邻。在5 mM K⁺培养基中恢复一段时间后，突触小泡数量和突触终末形状恢复正常。当在去极化和恢复过程中将辣根过氧化物酶（HRP）作为细胞外示踪剂加入培养基中时，相当一部分小的突触小泡含有反应产物。标记物也存在于包被小泡和池中。在含有Co²⁺的培养基中去极化或未去极化而暴露于HRP的神经元中，含有标记突触小泡的很少。标记小泡的比例在突触和曲张体中没有显著差异，也不随神经元的递质类型而一致变化。这些观察结果与以下假设一致：节后交感神经元的突触和曲张体通过小突触小泡的胞吐作用释放递质，并且至少一些新的小泡是由神经终末膜形成的。
