EFFECTS OF PHENYTOIN ON THE AMYGDALA NEURONS IN-VITRO

The present study was aimed at elucidating the possible mechanisms und erlying the anticonvulsant efficacy of phenytoin Sodium channel using intracellular recording techniques in the in vitro amygdalar channel d alar slice preparation. Synaptic response mediated by the N-methyl-D-a spartate (NMDA) receptor (EPSPNMDA) was isolated pharmacologically by application of a solution containing non-NMDA receptor antagonist 6-cy ano-7-nitroquinoxaline-2,3-dione (10 mu mol/l) and gamma-aminobutyric acid(A) receptor antagonist bicuculline (20 mu mol/l). Phenytoin inhib its the amplitude of EPSPNMDA without affecting the postsynaptic depol arization induced by exogenous application of NMDA, In addition, pheny toin increases the magnitude of paired-pulse facilitation which is con sistent with a presynaptic mode of action. These results suggest that inhibition of transmitter release due to presynaptic blockade of Na+ a nd/or Ca2+ channels may account largely for the anticonvulsant efficac y of phenytoin.