title: Activity-dependent depression of nerve action potential by phenytoin.
abstract: The action of the anticonvulsant drug phenytoin was investigated on the responsiveness of isolated amphibian and human nerves to repetitive stimulation. At low frequencies of stimulation (0.5-25 Hz) the drug (at a concentration of 0.1 mM) had no notable effect on the compound nerve action potential. By contrast, at higher rates of stimulation (50-300 Hz), it produced a progressive decrease in amplitude and integral of the compound action potential. This effect was positively correlated with the frequency of nerve activation and was markedly enhanced by elevating the extracellular K+ concentration. Thus, phenytoin induces a use- and frequency-dependent depression of axon conduction, which may contribute to its preferential suppression of the spread of high-frequency seizure discharge in the brain.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D007866:Leg / Q000294:innervation; D009119:Muscle Contraction; D009420:Nervous System / Q000187:drug effects*; D009424:Nervous System Physiological Phenomena; D010672:Phenytoin / Q000494:pharmacology*; D011895:Rana ridibunda
chemical_list: D010672:Phenytoin