Neural cell adhesion molecules, neuronal development and lead toxicity.

The major families of neural cell recognition molecules and the mechanisms by which they regulate neural development are described. The role of the neural cell adhesion molecule (NCAM) isoforms in organizing tissue structure and pattern is discussed in detail and their degree of sialylation is proposed to regulate the intimacy of cell-cell interaction, including that of synapse formation. The ability of chronic low level lead to impair normal NCAM sialylation pattern during postnatal development is discussed and this is suggested to perturb synapse selection procedures in a manner which may account for subsequent learning deficits in the adult rodent. In support of this proposal, change in hippocampal NCAM sialylation is demonstrated to occur in the synapse-specific isoform during the acquisition and consolidation of a passive avoidance response in the adult rat.