Differential expression of immediate-early proteins in non-nerve cells after focal brain injury.

We investigated the expression of the immediate-early proteins (IEPs, Fos, Fos B, Jun, Jun B, Jun D, Krox 20 and Krox 24) in non-nerve cells in rat brain after mechanical brain injury. Injury produced by infusion of 5 microliters of saline into the hippocampus produced a time-dependent expression of Fos, Jun and Krox 24, but not Fos B, Krox 20 or in non-nerve cells around the wound margin, in cells lining the lateral and third ventricles and in cells in the pial surfaces of the brain. Jun B and D were weakly induced in non-nerve cells 1-4 hr after brain injury. This differential expression of IEPs in non-nerve cells contrasted with neurons which expressed all IEPs measured. Thus, brain injury is associated with a differential expression of IEPs in non-nerve cells around the wound. The functional implications of this IEP expression after brain injury are presently unclear, but may be related to cellular proliferation after brain injury.