Developmental regulation of neurotransmitter phenotype

The extraordinary scope of neuronal plasticity has been appreciated only recently. The neuron is capable not only of altering structure and function quantitatively, but also of undergoing phenotypic transformation under appropriate circumstances. It is now well established from in vivo and in vitro studies that neurons may change transmitters, and thus phenotypes, during a relatively prolonged period of life. This, of course, has raised the possibility that neurons can change a variety of functions and capabilities, and that, for example, recovery after illness or regeneration after injury may be induced by appropriate treatments. In turn, a central issue in understanding the regulation of phenotypic expression in neurons, as well as other systems, concerns the relationship of intrinsic cellular information to environmental factors.