A possible role of a GABAergic mechanism in the convulsant action of RO5-4864.

The purpose of the present investigation was to determine the possible role of GABAergic mechanism in the convulsant action of RO5-4864. Benzodiazepines (BZ) and other agents which facilitate central GABAergic transmission delayed the onset of facial and forelimb clonus, whereas tonic hind limb extension was blocked in a dose-dependent manner. RO5-4864-induced convulsions were blocked by diazepam, clonazepam, pentobarbital, ethanol and amino-oxyacetic acid (AOAA). RO5-4864-induced convulsions were not blocked by the BZ antagonist RO15-1788. Specifically, RO15-1788 caused a decrease in the onset of severity component of tonic seizures, which tended to become generalized and precipitated in a tonic extension of the hindlimbs. Further, subconvulsive doses of a direct GABA receptor antagonist, bicuculline, enhanced the proconvulsant action of RO5-4864, indicating thereby a potential antagonism of the central GABAergic transmission. These observations strongly suggest that RO5-4864 probably elicits convulsions by selective impairment of the GABAergic transmission.