ACTION OF ANTIEPILEPTIC AND ANESTHETIC DRUGS ON NA-SPIKES AND CA-SPIKES IN MAMMALIAN NON-MYELINATED AXONS

The actions of the antiepileptic drugs phenytoin, carbamazepine and phenobarbitone, and the local anaesthetic drugs lignocaine and procaine on sodium-dependent and calcium-dependent compound action potentials (Na- and Ca-spikes) have been compared in rat preganglionic cervical sympathetic nerves, using extracellular recording techniques. There was no discernible difference in the frequency dependence of Na-spike block over the frequency range 0.2-20 Hz between these two groups of drugs. However the antiepileptic drugs were more potent blockers of the Ca-spike whereas the local anaesthetics were more potent on the Na-spike. It is proposed that a dual action of antiepileptics, a frequency-dependent block of sodium currents combined with a block of calcium currents, may explain their efficacy in the treatment of seizures. © 1990.