PROBABILITY OF QUANTAL SECRETION AT NEUROMUSCULAR SYNAPSES

研究突触传递的经典准备是两栖动物的神经肌肉接头，这方面的实验数据最多。这种突触有助于发现递质是以包或量子的形式释放的，这发生在神经末梢的专门释放部位，并且肌肉细胞上的受体分子被战略性地放置以接收递质。我们对这种突触的研究表明，每个释放位点都有不同的量子分泌概率，并且这种概率与释放位点的宽度相关。最近，我们已经表明，虽然量子的大小不会在相邻的释放位点之间变化，但量子被释放的区域确实会在位点之间变化。量子分泌的概率与该面积成正比，释放位点处存在的囊泡的数量也是如此。在这个项目中，我们打算将这种分泌的概率与调节量子释放的蛋白质联系起来，特别是这些蛋白质如何相互作用，以确定脉冲通过后释放部位的概率增加的时间过程。脉冲序列对这种概率的影响也将被描绘出来，特别是在这些脉冲序列期间进入终点站的钙如何决定在脉冲序列停止后概率的长期增强。这项研究将为运动神经末梢的分泌提供分子描述。

The classical preparation for the study of synaptic transmission is the amphibian neuromuscular junction, for which there is the largest body of experimental data. This synapse was instrumental in the discovery that transmitters are released in packets or quanta, that this occurs at specialized release sites in the nerve terminal, and that receptor molecules on the muscles cells are strategically placed to receive the transmitter. Our work on this synapse has shown that each of these release sites have different probabilities for the secretion of a quantum and that this probability is correlated with the width of the release site. More recently we have shown that, whilst the size of a quantum does not vary between adjacent release sites, the area over which the quantum is released does vary between sites. The probability of quantal secretion is proportional to this area, as is the number of vesicles present at the release site. In this project we intend to relate this probability of secretion to the proteins that regulate the release of a quantum and in particular how these proteins interact to determine the time course of increase in probability at a release site after the passage of an impulse. The affects of trains of impulses on this probability are also to be delineated, in particular how the calcium which enters the terminal during these trains determines a long-term enhancement in probability after the train has ceased. This research will provide a molecular description of secretion from motor-nerve terminals.