title: Analysis of the action of 4-aminopyridine during repetitive stimulation at the neuromuscular junction.
abstract: 4-Aminopyridine (4-AP) increased the quantal content (m) of end-plate potentials (e.p.p.s) evoked by continual stimulation (0.2--25 Hz) in frog end-plates depressed by Mg2+. The increase in m was due to an increase in the binomial parameter n. This was interpreted to mean that 4-AP increased the number of activated release sites. In junctions blocked by d-tubocurarine, 4-AP first increased and then decreased the amplitude of e.p.p.s. elicited during a train of stimuli of increasing frequency, indicating that 4-AP increased transmitter release more than mobilization.
mesh_terms: D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000378:metabolism; D011893:Rana esculenta
chemical_list: D000631:Aminopyridines; D018377:Neurotransmitter Agents