Functional role of GABA transporters for kindling development in GLAST KO mice

Kindling-induced after discharge in electroencephalograms depends on the protein associated with glutamatergic and/or GABAergic neuronal transmission. In glutamate transporter knockout (GLAST KO) mice, the kindling phenomena in GLAST KO developed more slowly while the after discharge duration (ADD) was briefer than that of the control C57BL-6J mice. These findings indicate that either the excitatory function was suppressed or the inhibitory function was enhanced in GLAST KO kindling. To explain these phenomena, we used Western blotting to evaluate the alterations in the expression of hippocampal GABA transporter proteins, and the estimation of the effect on the process of epileptogenesis. Although no alterations were observed in the GAT-3 expression, the hippocampal GAT-1 expression was significantly suppressed in comparison to that of C57BL-6J mice. A decreased GAT-1 level in the hippocampus, which might be associated with the increased extracellular GABA level, may therefore inhibit both ADD and seizure propagation as shown by the amygdaloid kindling phenomenon observed in GLAST KO mice.