GABAergic system in substantia innominata inhibits the secondary generalization of amygdaloid kindled seizure: Studies using the intracerebral microinjection of GABAergic drugs

The role of substantia innominata in secondary generalization of amygdaloid kindled seizure was studied in cats and rats. Effects of the intracerebral injection of muscimol, a direct GABA agonist, and gabaculine, a GABA aminotransferase inhibitor, on amygdloid kindled seizure were examined. In addition, changes of regional brain GABA content after gabaculine injection into the substantia innominata were determined in rats. The prolongation of the latency to the onset of generalized seizure or the suppression of generalized convulsion was observed after the intra-substantia innominata injection in cats. In contrast, afterdischarge triggering threshold was elevated after the intraamygdaloid injection. These effects were also observed in rats, the former effects were parallel to the increase of GABA content in the substantia innominata and frontal cortex, the latter effects were parallel to the increase of GABA content in the amygdala. The GABA system in substantia innominata might play an inhibitory role for the secondary generalization of amygdaloid kindled seizure.