[Role of cell-milieu interactions in the differentiation of nerve cells]

In this review some aspects of nerve cell development are studied from the point of view of the role of the environment on differentiation processes. In the first part, attention is focused on the early stages, with special emphasis on the commitment of the cells coming from the neural crest to acquire and keep a specialized phenotype. In the second part, attempts were made to understand the mechanisms of action of specific growth factors, the Nerve Growth Factor (NGF) being taken as a model molecule. Information presently available is presented on factors that may be implicated in the development of cell types other than those NGF-sensitive, with considerations as to whether the notion of specific growth factors can be generalized to all nervous cell types or not.