Presynaptic and postsynaptic depressant effects of phenytoin sodium at the neuromuscular junction.
1. Phenytoin sodium, 10 micrograms/ml (3.6 x 10(-5) M), reduces the amplitude of endplate potentials in mouse sternomastoid neuromuscular junctions. 2. The reduction in amplitude is due to a reduction both in the quantal content of endplate potentials and in the amplitude of the voltage response to quanta of acetylcholine. 3. The reduction caused by phenytoin in the amplitude of spontaneous miniature end plate potentials was due to a reduction in the time constant of decay of miniature endplate currents. 4. It is concluded that phenytoin depresses neuromuscular transmission by reducing both the amount of acetylcholine secreted in response to an action potential and by reducing the lifetime of postsynaptic channels activated by acetylcholine.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009045:Motor Endplate / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects*; D010672:Phenytoin / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects; D013997:Time Factors
D010672:Phenytoin; D000109:Acetylcholine