ACTIVITY-DEPENDENT DEVELOPMENT OF THE VERTEBRATE NERVOUS-SYSTEM

This chapter discusses the experiments on the role of activity during development from many different systems, principally the neuromuscular junction (NMJ), the retinal/tectal system, the visual cortex, long-term potentiation (L'TP) in the hippocampus, and a number of other vertebrate systems where this question is studied. Results are compared across systems in an effort to derive common properties of activity-dependent regulation of synaptic connections between neurons during development, and to reveal important differences among the phenomena in different systems. Several biochemical processes that may participate in activity-dependent changes in synaptic strength, synaptogenesis, and synapse elimination are considered. Central to many of these biochemical pathways is intracellular free calcium. Sources of calcium influx into the neuron (voltage-sensitive calcium channels and Nmethyl- D-aspartic acid (NMDA) channels) and several intracellular actions of this cation are considered. NMDA channels and voltage-sensitive calcium channels differentiate between signals (one responding based on voltage, and the other requiring the association between transmitter and depolarization), but they both affect the same second messenger (calcium) in similar ways. © 1992 Academic Press Inc.