PHENYTOIN, AN ANTIEPILEPTIC DRUG, COMPETITIVELY BLOCKED NON-NMDA RECEPTORS PRODUCED BY XENOPUS-OOCYTES

The blocking effect of phenytoin (PHT) and other antiepileptic agents on the glutamate receptors was investigated under voltage-clamp condit ions using Xenopus oocytes that translated ddY-stock mouse brain mRNA. PHT shifted the concentration-response curve for kainate to right wit hout significant block on the maximum response obtained, indicating th at PHT competitively blocks the non-NMDA receptors. An apparent dissoc iation constant of PI-IT was 1.9 x 10(-4) M. The block was voltage-ind ependent. Other antiepileptic agents examined hardly blocked the kaina te responses except phenobarbital that blocked the responses. The poss ibility that the competitive block constitutes a part of the antiepile ptic action of PHT was discussed.