Journal of Neuroscience, Vol 2, 1465-1473, Copyright © 1982 by Society for Neuroscience
Single cholinergic receptor channel currents in cultured human muscle
MB Jackson, H Lecar, V Askanas and WK Engel
Single cholinergic channel currents were recorded in adult human muscle
tissue culture. The agonists suberyldicholine and carbamylcholine produce
channels with the same conductance as channels produced by acetylcholine
but with different closing kinetics. The antagonist tubocurarine, alone or
mixed with suberyldicholine, activates channels which close very rapidly.
For agonist-activated channels, the distribution of open state lifetimes
shows deviations from the usual single exponential form. An excess of short
duration openings indicates the presence of an additional faster kinetic
process. The lifetime distribution data can be interpreted in terms of
varying proportions of slow and fast components which are present in a
ratio determined by curve-fitting the appropriate two-exponential function
to observed open time distributions. This ratio shows great variability in
muscle from older cultures, but the fast and slow time constants are
relatively constant. The observation of double exponential open time
distributions indicates that the mechanism of channel closing is more
complicated than earlier evidence indicated.