Differential induction of c-Fos, c-Jun and Jun B in the rat central nervous system following unilateral entorhinal cortex lesion

In order to identify some of the molecular mechanisms that occur after a ce ntral nervous system trauma, the immediate early gene encoded proteins c-Fo s, c-Jun and Jun B were analysed by immunocytochemistry following unilatera l entorhinal cortex lesion (controls, 30 min, 2, 5, 12 and 24 h, two, six, 10 and 14 days, four weeks and six months postlesion). In the dentate gyrus , c-Fos was induced in some supragranular neurons (30 min), massively expre ssed in granule cells ipsilaterally to the lesion (2 h), expressed in hilar neurons (5 h and two days) and was absent at all later stages. A basal exp ression of c-Jun was found in dentate granule cells of controls, which was strongly increased on the lesion side (2 h) and on the side contralateral t o the lesion (12 h). c-Jun expression returned to control levels by 24 h. J un B was induced in granule cells ipsilateral to the lesion within 2 h and was back to control levels by 5 h. In the lateral septal area, c-Fos and c- Jun were induced 30 min postlesion and decreased rapidly thereafter. In the cerebral cortex, a widespread induction of c-Fos and c-Jun occurred within 30 min after entorhinal cortex lesion and this up-regulation lasted until two days postlesion. These data indicate that electrolytic lesion of the entorhinal cortex leads to a rapid and widespread induction of c-Fos, c-Jun and Jun B. Within the denervated fascia dentata, some of these changes may be linked to the reorg anization processes following the lesion. Alternatively, the alterations in immediate early gene expression reported here may be due to changes in syn aptic activity or postlesional seizures which occur in this lesioning parad igm. (C) 1999 IBRO. Published by Elsevier Science Ltd.