Fahim M A
Department of Physiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Abu Dhabi.
Cell Mol Biol. 1992 Jul;38(4):385-93.
The spontaneous quantal release of neurotransmitter and the fine structure of a glutamatergic synapse has been examined in the presence of ionophore X-537A. Bath applications of X-537A to extensor tibiae nerve-muscle preparations of locust, Schistocerca gregaria, increased the frequency of miniature excitatory post-synaptic potentials (min. e.p.s.p.'s). This action was completely reversible, if preparations were exposed to ionophore for less than 60 min. Application of ionophore for longer times, i.e., longer than 60 min., transiently elevated min. e.p.s.p. frequency to greater than 100/s. Following this period of high activity, miniature frequency declined to 0.4/s and were mostly of "giant" miniature potentials type. The frequency and amplitude of these "giant" miniature potentials remained unchanged after subsequent washing with standard saline. Exposure of nerve terminals to ionophore for 60 min. produced no ultrastructure changes. Longer ionophore treatments, however, led to depletion of synaptic vesicles, damaged mitochondria and disintegration of microtubules and neurofilaments within nerve terminals, suggesting irreversible changes at the locust neuromuscular junction.
在离子载体X - 537A存在的情况下，研究了神经递质的自发量子释放和谷氨酸能突触的精细结构。将X - 537A浴用于沙漠蝗（Schistocerca gregaria）的胫节伸肌神经 - 肌肉标本时，微小兴奋性突触后电位（min. e.p.s.p.）的频率增加。如果标本暴露于离子载体的时间少于60分钟，这种作用是完全可逆的。离子载体作用较长时间，即超过60分钟时，微小兴奋性突触后电位频率会短暂升高至大于100/秒。在这段高活性期之后，微小电位频率降至0.4/秒，且大多为“巨型”微小电位类型。用标准盐水随后冲洗后，这些“巨型”微小电位的频率和幅度保持不变。神经末梢暴露于离子载体60分钟未产生超微结构变化。然而，离子载体处理时间更长会导致突触小泡耗尽、线粒体受损以及神经末梢内微管和神经丝解体，提示在蝗虫神经肌肉接头处发生了不可逆变化。
