Activation by curare of acetylcholine receptor channels in a murine skeletal muscle cell line.
Curare action on nicotinic acetylcholine receptors has a number of facets, of which the best known is competitive antagonism. Here we describe the weak agonist action of 10(-5) M curare on the murine skeletal muscle cell line, G8. Although curare induces no depolarization in G8 cells, single-channel recordings reveal short-lived curare-induced currents. A feature of these brief events is the multiplicity of conductance levels (of the four levels with conductances of 48, 37, 14, and 6 pS, none had a lifetime greater than 1.5 ms). Most well-resolved events (about 17% of which are to a subconductance) last less than 0.5 ms, with activation occurring predominantly as isolated events rather than in bursts. Agonism is not, however, a high probability action for curare: calculations based on the frequency of events at half-saturating conditions suggest that curare-induced channel openings occur during less than 1% of acetylcholine receptor-curare binding episodes. The outcome is (a) an agonist action too feeble to perturb the membrane voltage and (b) a powerful competitive antagonist action.
Morris
C E
CE
Biology Department, University of Ottawa, Ont., Canada.
Montpetit
M R
MR
Sigurdson
W J
WJ
Iwasa
K
K
D000818:Animals; D002460:Cell Line; D003472:Curare / Q000494:pharmacology*; D004594:Electrophysiology; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008566:Membranes / Q000502:physiology; D051379:Mice; D009132:Muscles / Q000378:metabolism*; D011247:Pregnancy; D011950:Receptors, Cholinergic / Q000378:metabolism*
D011950:Receptors, Cholinergic; D003472:Curare