Widespread neuronal expression of c-Fos throughout the brain and local expression in glia following a hippocampal injury.

Fos oncoprotein is an immediate early gene product and a marker of cell activation following a variety of insults. We have previously shown that a mechanical lesion to the hippocampus of adult mice induces a neuronal expression of the cytokines interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF alpha) whereas a lesion to the striatum does not. The role of these inflammatory cytokines in the pathophysiology of central neurons is still unclear. The present work was undertaken to study a possible correlation between the central expression patterns of c-Fos on the one hand and IL-1alpha and TNF alpha on the other hand. We show that Fos is expressed in a majority of brain neurons after a unilateral lesion to the hippocampus whereas it is confined to the site of injury when applied to the striatum, as previously described for the expression of the cytokines.