Induction of Fos in glia-like cells after focal brain injury but not during wallerian degeneration.

Focal brain injury or perforant-path transections respectively led to an increase in the number of glial-fibrillary acidic protein (GFAP)-immunopositive astrocytes around the focal wound or in the terminal fields of the perforant path in the dentate molecular layer. This GFAP accumulation occurred 48-72 h after focal brain injury or perforant-path transection (wallerian degeneration). Focal brain injury also led to an accumulation of c-fos protein (Fos) in glial cells, ependyma and cells in the pia mater of the brain within 6 h of injury and this effect dissipated within 72 h. However, perforant-path lesions were not associated with accumulation of Fos in glial cells in the dentate molecular layer suggesting that c-fos induction in glial cells after injury is not necessary for GFAP accumulation. Induction of Fos in glia, ependyma and pia after focal brain injury may be associated with proliferation of these cells after injury.