ALTERATIONS OF GABA(A)BETA-2 3 IMMUNOREACTIVITY IN THE DENTATE GYRUS AFTER PERFORANT PATHWAY LESION/

IMMUNOCYTOCHEMICAL techniques were employed to examine the changes in the GABA receptor subunits beta 2/3 within the dentate gyrus of the ra t brain 1, 3, 7, 14, 30 and 90 days after a unilateral perforant pathw ay lesion. Three days post-lesion we observed a decrease in beta 2/3 i mmunolabeling in the inner molecular layer of the dentate gyrus follow ed by a comparable decrease in the outer molecular layer 7 days post-l esion. These decreases were transient; 30 and 90 days post-lesion, bet a 2/3 immunolabeling appeared similar to controls in the inner portion of the molecular layer, while in the outer region the labeling was in creased. In this latter region we also observed a dense band of AChE f ibers. Following survival times of 3 days we observed a diffuse staini ng of the neuropil in the hilar region, and a dense amorphous accumula tion of peroxidase reaction product in the polymorphic region. These r esponses were transient and by 14 days the hilar/polymorphic region ap peared indistinguishable from controls. These data suggest a unique pa ttern of immunoabeling in the molecular and polymorphic region in resp onse to perforant pathway lesion. A putative explanation for this resp onse is discussed.