Ethanol Inhibits Epileptiform Activity and NMDA Receptor-mediated Synaptic Transmission in Rat Amygdaloid Slices

The effect of ethanol on the epileptiform activity induced by Mg(++)-free solution was studied in rat amygdalar slices using intracellular recording techniques. The spontaneous and evoked epileptiform discharges consisting of an initial burst followed by afterdischarges were observed 20-30 min after switching to Mg(++)-free medium. Superfusion with ethanol (20-100 mM) reversibly reduced the duration of spontaneous and evoked bursting discharges in a concentration-dependent manner. Synaptic response mediated by N-methyl-D-aspartate (NMDA) receptor activation was isolated by application of a solution containing the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and either in Mg(++)-free solution or in the presence of 50 microM bicuculline. Application of ethanol reversibly suppressed the duration of NMDA receptor-mediated synaptic response. These results suggest that intoxicating concentrations of ethanol possess anticonvulsant activity through blocking the NMDA receptor-mediated synaptic excitation. In addition, the observed effect of ethanol on NMDA receptor-mediated synaptic response could be relevant to the cognitive and behavioral manifestations seen in some alcoholics.