Selective changes in gamma-aminobutyric acid type A receptor subunits in the hippocampus in spontaneously seizing rats with chronic temporal lobe epilepsy.

Changes in the structure and function of inhibitory GABA(A) receptors may contribute to epileptogenesis. We have used the in situ hybridization technique to study GABA(A) receptor alpha2, alpha4, beta3 and gamma2 subunit mRNA expression in the hippocampus of spontaneously seizing rats with chronic temporal lobe epilepsy. In control rats, all four subunit mRNAs were expressed in the hippocampal subregions but the intensity of expression varied significantly between the subfields. In epileptic rats, alpha2 expression was decreased in CA3c, and alpha4 in CA1, but beta3 was increased in all subregions, in particular in the granule cell layer. Our results suggest that GABA(A) receptor undergoes region selective subunit changes during epileptogenesis in the hippocampus of rats with chronic temporal lobe epilepsy.