Opposite Changes in GABAA Receptor Function in the CA1‐3 Area and Fascia Dentata of Kindled Rat Hippocampus

: Muscimol‐stimulated radiotracer 36Cl− uptake in synaptoneurosomes was used to investigate the function of the GABAA 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 collateral fibers. Two kindled groups were studied: (a) 24 h after the last generalized tonic‐clonic seizure [fully kindled (FK) stage] and (b) 28 days after the last generalized seizure (long‐term stage). Synaptoneurosomes were prepared in parallel from subslices of the CA1‐3 area and fascia dentata. In FK animals, the muscimol‐stimulated 36Cl− uptake was significantly reduced by 21% in the CA1‐3 area in comparison with nonstimulated controls, whereas a significant increase of 29% was found in the fascia dentata. Significant changes were no longer present at 4 weeks after the last generalized seizure. The observed changes in muscimol‐stimulated 36Cl− uptake at the FK stage closely parallel the recently observed changes in [3H]muscimol binding in the CA1 area and fascia dentata. These results indicate that kindling causes a transiently decreased GABAA receptor‐mediated function in the CA1‐3, in contrast to an increased GABAA receptor‐mediated function in the fascia dentata.