THE EFFECTS OF ANTICONVULSANT DRUGS ON NMDA-EPSP, AMPA-EPSP, AND GABA-IPSP IN THE RAT HIPPOCAMPUS

The effects of phenobarbital, phenytoin, and valproic acid on pharmaco logically isolated NMDA-EPSP, AMPA-EPSP, and GABA-IPSPs were examined in rat hippocampal slices. Phenobarbital (0.05 mg/ml) had no effect on the NMDA-EPSP, but decreased the slope of the AMPA-EPSP by 13.4% and facilitated the GABA-IPSP slope by 77.12%. Phenytoin (0.02 mg/ml) had no effects on the NMDA-EPSP, AMPA-EPSP, or GABA-IPSP. Valproic acid (0 .1 mg/ml) decreased the NMDA-EPSP slope by 14.3%, increased the GABA-I PSP slope by 54.34%, and had no effect on the AMPA-EPSP. These data su ggest that the mechanisms of action of these anticonvulsant drugs may be via their actions on different neurotransmitter systems or ion chan nels. Copyright (C) 1997 Elsevier Science Inc.