SYNAPSE FORMATION AND GROWTH IN AN AUTONOMIC GANGLION

我研究的长期目标是了解 神经元之间突触形成的基础 胚胎发生 本提案的具体目标是：（1）完成 变性后大鼠心神经节突触生长的分析 非洲爪蟾和2）研究的初始形成和生长 在幼体动物中发育中的心脏神经节细胞上的突触。 在成熟 在动物中，单个神经元的神经支配是由一个 神经节前轴突，它提供所有的突触终扣上发现的 神经节细胞体 在变性后的生命中，突触的总面积 接触随着终扣数量的增加而增加， 数量与神经节细胞大小的增加完全匹配。 通过 研究神经节的主要突触输入的递质释放 细胞，并通过对生理特征细胞上的终扣进行计数， 应确定钮扣是否代表发射器的等量 释放以及它们是否代表突触生长的功能单位。 通过研究二倍体和更大的四倍体神经节的神经支配 细胞嵌合动物，我们希望确定的基础上， 变质后细胞大小和终核数量的补偿性生长 动物 神经节前轴突到达发育中的心神经节， 通过填充技术可视化，并将研究新生突触 从解剖学上和生理学上都是如此。 如何构建和释放 新形成的终扣与成熟终扣的性质比较？ 的 将分析幼虫动物中突触的生长，以了解 终扣是突触生长的单位， 突触发生 将通过生理学方法研究突触消除 技术，我们将问是否神经节细胞体是永远 由一个以上的节前轴突支配。 最后，我们将搜索 神经节细胞间的短暂连接 此类连接 通常被节前神经支配抑制，但也可能在 发展 这些研究将增加我们对突触如何在 神经元在发育过程中形成和生长。 他们还将确定 突触形成过程可能出错的阶段。

The long-range objective of my research is to understand the mechanisms that underlie the formation of synapses between neurons during embryogenesis. The specific objectives of this proposal are 1) to complete an analysis of synaptic growth in the cardiac ganglion of postmetamorphic Xenopus laevis and 2) to study the initial formation and the growth of synapses on developing cardiac ganglion cells in larval animals. In mature animals the innervation of individual neurons is dominated by a preganglionic axon which supplies all the synaptic boutons found on the ganglion cell body. During postmetamorphic life the total area of synaptic contact grows by an increase in bouton number, and the increase in bouton number is exactly matched by an increase in ganglion cell size. By studying transmitter release from the principal synaptic input to ganglion cells and by counting boutons on physiologically characterized cells, we shall determine whether boutons represent equivalent amounts of transmitter release and whether they represent the functional unit of synaptic growth. By studying the innervation of both diploid and larger tetraploid ganglion cells in chimeric animals, we hope to determine the basis of the compensatory growth of cell size and bouton number in postmetamorphic animals. The arrival of preganglionic axons in the developing cardiac ganglion will be visualized by filling techniques, and nascent synapses will be studied both anatomically and physiologically. How do the structure and release properties of newly formed boutons compare with those of mature ones? The growth of synapses in larval animals will be analyzed to learn whether boutons are the units of synaptic growth from the very onset of synaptogenesis. Synapse elimination will be investigated by physiological techniques, and we shall ask whether the ganglion cell body is ever innervated by more than one preganglionic axon. Finally, we shall search for transient connections between ganglion cells. Such connections are ordinarily suppressed by preganglionic innervation but may appear early in development. These studies will increase our understanding of how synapses between neurons form and grow during development. They will also identify the stages when the process of synapse formation may go awry.