Increase in glia-derived nerve growth factor following destruction of hippocampal neurons.

It is currently believed that under normal conditions hippocampal neurons synthesize nerve growth factor (NGF) which may provide trophic support for cholinergic neurons projecting from the basal forebrain. The concept that glial cells are mobilized to increase the production of NGF following destruction of hippocampal neurons was examined. Excitotoxin-induced destruction of the dorsal hippocampal neurons resulted in a massive and prolonged increase in NGF-like immunoreactivity (LI). Immunostaining for NGF-LI and the glial marker, glial fibrillary acidic protein (GFAP), revealed that the source of increased NGF-LI production following the lesion were reactive astrocytes. Thus, glial cells assume the role of providing trophic support following loss of target neurons.