Desensitization of the post-synaptic membrane of neuromuscular synapses induced by spontaneous quantum secretion of mediator.
Experiments on isolated frog neuromuscular junctions in voltage-clamped conditions demonstrated increases in the probability of spontaneous release of quanta of mediator, resulting in increases in the K+ ion concentration in the perfusion solution, and changes in the endplate miniature current amplitude induced by increased quantum generation were studied. Factors promoting the desensitization of the post-synaptic cholinergic membrane (inhibition of acetylcholinesterase and addition of proadifen) to levels greater than a certain (critical) frequency of endplate miniature current of the order of 50 spikes/sec were found to result in accumulation of activity and progressive reductions in the sensitivity of the post-synaptic membrane to the mediator acetylcholine.
Department of Normal Physiology, Kazan' State Medical University, Russia.
R A
RA
Giniatullin
L G
LG
Magazanik
D000109:Acetylcholine / Q000378:metabolism / Q000502:physiology*; D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001001:Anura; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D009045:Motor Endplate / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D011335:Proadifen / Q000494:pharmacology; D012584:Sciatic Nerve / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D013268:Stimulation, Chemical; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D002800:Cholinesterase Inhibitors; D004791:Enzyme Inhibitors; D011335:Proadifen; D000110:Acetylcholinesterase; D000109:Acetylcholine; D011188:Potassium