GLIAL-CELL HETEROGENEITY IN THE MAMMALIAN SPINAL-CORD

The vertebrate spinal cord is comprised of a complex array of differen t populations of neurons and axon tracts. Recent studies suggest that this complex neuronal cytoarchitecture is complemented by a similarly complex glial cytoarchitecture. Cultures of neonatal rat spinal cord c ontain multiple different classes of astrocytes. These distinct classe s of astrocytes have particular morphologies and arise from separate p recursors that proliferate in response to different mitogens. It seems likely that the individual classes of astrocytes will have regional l ocalization and will be involved in specific functions in the intact s pinal cord. In contrast to the significant diversity seen among astroc ytes, spinal cord oligodendrocytes in the embryonic animal appear to b e a relatively homogenous population of cells that proliferates in res ponse to known growth factors at particular stages of maturation. An i mportant future challenge in glial cell biology is to define clearly t he functional roles of individual populations of astrocytes in the dev eloping adult, and injured spinal cord. Such information may ultimatel y lead to the ability to modulate astrocytic function at a cellular le vel during aberrant development and following injury to the adult spin al cord.