Transmitting transmitter phenotypes in brain development.

Little is known about the transmitter choice of neurons in the central nervous system. Recent evidence suggests that precursor cells in the mammalian neocortex are multipotential and generate GABAergic as well as glutamatergic neurons. Environmental interactions within the proliferative zone seem to specify the transmitter phenotype of the neurons generated by the multipotential precursor cells. Precursor cells are restricted in the ventricular zone of a given region in the forebrain and do not intermingle with precursor cells from the adjacent regions. They are thus exposed to distinct region-specific environmental influences that instruct the different neuronal phenotypes found in different regions of the adult brain. Amongst the factors that influence the transmitter choice of early neuroblasts are transmitters themselves. Activity-dependent mechanisms mediated by a variety of neurotransmitters and their receptors could be the key players in specifying neuronal phenotypes at early developmental stages in the ventricular zone.