title: Phenytoin reduces frequency potentiation of synaptic potentials at the frog neuromuscular junction.
abstract: The action of the commonly used antiepileptic drug phenytoin on frequency potentials was studied at the frog neuromuscular junction. Whereas the drug, at concentrations of 0.1-0.3 mM, had only a slight effect on EPPs evoked by nerve stimulation at a frequency of 0.5 Hz, it strongly suppressed their potentiation during tetanic nerve stimulation at 30 Hz. The post-tetanic potentiation of the EPPs was also reduced by the drug. These effects occurred without a blockade of invasion of the nerve impulse into the presynaptic terminal during the tetanus, and thus indicate a specific frequency-dependent depressant action of the drug on neurally-evoked transmitter release.
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects; D009132:Muscles / Q000294:innervation; D009469:Neuromuscular Junction / Q000187:drug effects*; D010672:Phenytoin / Q000494:pharmacology*; D011895:Rana ridibunda; D013569:Synapses / Q000187:drug effects*
chemical_list: D010672:Phenytoin