OPPOSITE CHANGES IN GABA(A) RECEPTOR FUNCTION IN THE CA1-3 AREA AND FASCIA-DENTATA OF KINDLED RAT HIPPOCAMPUS

Muscimol-stimulated radiotracer Cl-36(-) uptake in synaptoneurosomes w as used to investigate the function of the GABA(A) receptor complex in the CA1-3 area and fascia dentata (granular and molecular layers and hilus) of rats kindled by stimulation, twice a day, of the Schaffer co llateral fibers. Two kindled groups were studied: (a) 24 h after the l ast generalized tonic-clonic seizure [fully kindled (FK) stage] and (b ) 28 days after the last generalized seizure (long-term stage). Synapt oneurosomes were prepared in parallel from subslices of the CA1-3 area and fascia dentata. In FK animals, the muscimol-stimulated Cl-36(-) u ptake was significantly reduced by 21% in the CA1-3 area in comparison with nonstimulated controls, whereas a significant increase of 29% wa s found in the fascia dentata. Significant changes were no longer pres ent at 4 weeks after the last generalized seizure. The observed change s in muscimol-stimulated Cl-36(-) uptake at the FK stage closely paral lel the recently observed changes in [H-3]muscimol binding in the CA1 area and fascia dentata. These results indicate that kindling causes a transiently decreased GABA(A) receptor-mediated function in the CA1-3 , in contrast to an increased GABA(A) receptor-mediated function in th e fascia dentata.