Cell Biological Aspects of Neuronal Communication: Trophic Interactions in the Developing and Adult Nervous System

Abstract

Receiving signals from the outside of the organism and from many parts of the body, integrating them with other signals and stored information, and generating a motor output or memory trace is the basic function of the nervous system. This nervous activity is represented by electrical impulses flowing along nerve fibers (axons and dendrites) and by chemical signals (neurotransmitters) at the site of transmission from one nerve cell to another or to an effector cell. However, during the development of the nervous system as well as for its maintenance in the adult stage additional ways of inter- and intracellular communication seem to be required. Roughly, three levels of communication can be distinguished in the nervous system which differ in the kind of information that is transmitted, the way it is encoded, and the cell biological mechanisms involved (Table I).