Action of antiepileptic and anaesthetic drugs on Na- 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.
Elliott
P
P
M.R.C. Neuropharmacology Research Group, School of Pharmacy, University of London, Brunswick Square, U.K.
D000200:Action Potentials / Q000187:drug effects; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D002220:Carbamazepine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005479:Flurazepam / Q000494:pharmacology; D008012:Lidocaine / Q000494:pharmacology; D011343:Procaine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D000777:Anesthetics; D000927:Anticonvulsants; D002220:Carbamazepine; D011343:Procaine; D008012:Lidocaine; D012964:Sodium; D014700:Verapamil; D005479:Flurazepam; D002118:Calcium