Glial heterogeneity and developing neurotransmitter systems.

Evidence from the developing serotonergic system provides support for the working hypothesis that an important function of receptors expressed by developing glia may be to mediate the effects of neurotransmitters on growth and differentiation of the neurons that utilize them, by regulating the production of glial-derived neurotrophic factors. Regional heterogeneity of glial expression may reflect the specific roles played by these receptors within different compartments of a developing neurotransmitter system. During the construction of neural pathways, the specificity of these neurotransmitter-mediated neuronal-glial interactions would require appropriate spatiotemporal expression of glial receptors and neurotrophic factors, as well as specificity of these factors for neurons of appropriate neurotransmitter phenotypes.