22 Synaptic Transmission

Abstract

I. INTRODUCTION
Intercellular communication between neurons and their target cells is primarily accomplished by the regulated release of neurotransmitters at synapses. Extensive study of this vesicular-mediated process has revealed that many of the molecular components of the release apparatus are highly conserved in metazoans (Bennett and Scheller 1994; Südhof 1995). In vertebrates, biochemical approaches have led to the identification of components that participate in the release process, whereas the study of synaptic transmission in Caenorhabditis and Drosophila has proceeded in large part using genetic approaches. Each of these approaches has yielded insights. An extensive array of biochemically defined protein-protein interactions has provided the framework for building mechanistic models of neurotransmitter release. The genetic approach has identified novel components that eluded biochemical characterization and has provided functional data to refine the models. Clearly, a complete analysis at the functional level will require the use of electrophysiological techniques, and although such methods are becoming available for C. elegans (Avery et al. 1995b; Avery and Thomas, this volume), they are more advanced in other organisms. In concert, the study of synaptic transmission in C. elegans, Drosophila, and vertebrates has begun to provide an outline of the molecular details of synaptic vesicle function and neurotransmitter release.

The entire nervous system of the adult C. elegans hermaphrodite, which contains 302 neurons, has been reconstructed from serial section electron micrographs (White et al. 1986). The reconstruction yielded not only a connectivity pattern, but also an excellent understanding of the structure of synapses in C. elegans. The...