HETEROGENEITY OF EXPRESSION OF NEUROPEPTIDE GENES BY ASTROCYTES - FUNCTIONAL IMPLICATIONS

A specific subset of neuropeptides are expressed in astrocytes, with s pecificity in terms of both brain region and gene, as well as with spe cific developmental patterns: the overall pattern of expression is thu s heterogeneous. These neuropeptides have been demonstrated to have a number of trophic effects, including regulation of cell number, of len gth of axons and dendrites, and of neuronal phenotype. The development al regulation of expression of neuropeptides in astrocytes further sup ports functional roles for the neuropeptides as trophic modeling facto rs. Not all the trophic effects have to be stimulatory and evidence su ggests that opioid peptides may function to prune dendrites or decreas e cell numbers in order to modulate or shape the nervous system. In ad dition to roles during development, preliminary experiments suggest th at astrocyte neuropeptide expression turns back on in the adult brain following injury, suggesting that the neuropeptides may play a role in supporting survival or recovery of damaged neurons. The heterogeneity of neuropeptide expression in astrocytes must therefore contribute to the establishment and maintenance of the network of communication amo ng neurons and glia in the nervous system in ways we have yet to under stand fully.