Low magnesium-induced epileptiform discharges in guinea pig hippocampal slices: depression by the organic calcium antagonist verapamil.

The antiepileptic effects of the organic calcium channel blocker verapamil were tested in non-drug-induced epileptiform activities. Low Mg2+ epileptic field potentials (EFP) were elicited in hippocampal slices of guinea pigs. Verapamil reduced frequency of occurrence and amplitude of EFP until EFP failed. The EFP reappeared if verapamil was withdrawn from low Mg2+ solution. Elevating the KCl concentration from 4 to 8 mM resulted in shortening of the latency of EFP abolition by verapamil and prolongation of the depressive effects of verapamil following its withdrawal. The findings indicate that transmembraneous calcium fluxes play also an essential role in low Mg(2+)-induced epileptiform activities.