PARADOXICAL GABAERGIC FACILITATION ON SEIZURE DEVELOPMENT OBSERVED FROM BICUCULLINE-INDUCED EFFECTS ON VISUAL CORTICAL KINDLING AT SHORT INTERSTIMULUS INTERVALS IN CHRONICALLY PREPARED RABBITS

To investigate the influence of GABAergic function on seizure developm ent, the effects of bicuculline, a GABAa receptor antagonist, on visua l cortical and hippocampal kindling were examined in chronically prepa red rabbits. Kindling-inducing stimulations were repeated at 5-min int ervals. The changes in afterdischarge (AD) durations were compared bef ore and 30 min after a low (2 mg/kg) and high dose (5 mg/kg) i.p. inje ction of bicuculline solution. In the visual cortical kindling group, the AD durations were markedly shortened after the low dose bicucullin e injection, while bicuculline produced a prolongation of the AD durat ions in the visual cortical with the high dose injection and hippocamp al kindling groups. The low dose bicuculline-induced inhibition of vis ual cortical kindling suggests facilitative GABAergic action on seizur e development, while the drug-induced enhancement in the other groups reflects the well-known inhibitory GABAergic action.