This study examined the nature of the interactions of etifoxine, an anxiolytic and anticonvulsant compound, with the GABA(A) receptor/chloride channel complex. In membrane preparations of Sprague-Dawley rat cerebral cortex, etifoxine competitively inhibited the binding of [35S]t-butylbicyclophosphoro-thionate (TBPS), a specific ligand of the GABA(A) receptor chloride channel site. In vivo studies demonstrated an anticonvulsant effect of etifoxine (50 and 75 mg/kg, i.p.) against the clonic convulsions induced by TBPS in CD1 mice. Flumazenil (10 and 40 mg/kg, i.p.), an antagonist of benzodiazepine sites at GABA(A) receptors, had no effect on the action of etifoxine. These findings suggest that etifoxine exerts its effect by interacting with the Cl- channel of GABA(A) receptors and probably by facilitating GABAergic inhibition.
Read full abstract