A fundamental problem in neuroscience is the elucidation of the cellular and molecular mechanisms underlying the development and function of the nervous system. The complexity of organization, the heteroge neity of cell types and their interactions, and the difficulty of controlling experimental variables in intact organisms make this a formidable task. Because of the ability that it affords to analyze smaller components of the nervous system (even single cells in some cases) and to better control experimental variables, cell culture has become an increasingly valuable tool for...