This book consists of five sections. The first section details methods for analyzing both presynaptic and postsynaptic function and emphasizes the molecular aspects of synapses. It describes ongoing studies of neurotransmitter release, voltage- sensitive ion channels, and electronic transmission at gap junctions. The second section focuses on the growing menagerie of neurotransmitters: their catagorization into chemical families, their relation to ion channels, their modulation by second messenger systems and their role in pharmacologic action. The third section considers the important relationship of transmitter diversity and synaptic types to the behavior of actual cellular networks. All of the studies described in these sections point to the necessity of considering interactions between anatomy, chemistry, physiology and pharmacology if synaptic function is to be understood at any one of these levels of analysis.