Paradoxical GABAergic facilitation on seizure development observed from bicuculline-induced effects on visual...

To investigate the influence of GABAergic function on seizure development, the effects of bicuculline, a GABAa receptor antagonist, on visual cortical and hippocampal kindling were examined in chronically prepared rabbits. Kindling-inducing stimulations were repeated at 5-min intervals. The changes in afterdischarge (AD) durations were compared before and 30 min after a low (2 mg/kg) and high dose (5 mg/kg) i.p. injection of bicuculline solution. In the visual cortical kindling group, the AD durations were markedly shortened after the low dose bicuculline injection, while bicuculline produced a prolongation of the AD durations in the visual cortical with the high dose injection and hippocampal kindling groups. The low dose bicuculline-induced inhibition of visual cortical kindling suggests facilitative GABAergic action on seizure development, while the drug-induced enhancement in the other groups reflects the well-known inhibitory GABAergic action.