Bicuculline-induced blockade of neocortical rapid kindling suggesting facilitative GABAergic action on seizure development.

To investigate how GABAergic function affects seizure development, the effects of a GABA antagonist, bicuculline, on neocortical and hippocampal kindling were examined in chronically prepared rabbits. Kindling-inducing stimulations consisted of stimulus trains repeated at 5-min interstimulus intervals to produce so-called "rapid kindling". The changes in after-discharge (AD) durations induced by each of 15 trials of stimulus trains per session were compared before and 30 min after i.p. injection of bicuculline solution (2 mg/kg) in each of three kindling groups consisting of 5 rabbits each, i.e. visual cortical, motor cortical and hippocampal kindling groups. In the visual cortex and to a less extent, the motor cortex kindling groups, the AD durations were shortened after bicuculline injection and did not show the progressive prolongation seen before the injection. In contrast, the hippocampal kindling group showed a further marked prolongation of the AD durations after the injection. The bicuculline-induced blockade of neocortical kindling suggests facilitative GABAergic action on seizure development, while the drug-induced enhancement of hippocampal kindling reflects the known inhibitory GABAergic action.