Depression of synaptic transmission by diphenylhydantoin.
Diphenylhydantoin (phenytoin, DPH) depresses synaptic transmission at the frog neuromuscular synapse by presynaptic and postsynaptic mechanisms. In normal Ringer's solution the amplitude of the neurally evoked end-plate potentials and their quantal content are reduced. Somewhat paradoxically, miniature end-plate potential (mepp) frequency is increased by the drug. These effects could result if DPH blocked both calcium transport at the axonal membrane and intracellular calcium sequestration. Mepp amplitude is reduced, and DPH also induces nerve conduction block at high rates of stimulation. The relevance of these effects to the anticonvulsive activity of DPH is discussed.
D000818:Animals; D001001:Anura; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism; D010672:Phenytoin / Q000494:pharmacology*; D011894:Rana pipiens; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D018377:Neurotransmitter Agents; D010672:Phenytoin