Journal of Neuroscience, Vol 4, 70-74, Copyright © 1984 by Society for Neuroscience
Mobility of extrajunctional acetylcholine receptors on denervated adult muscle fibers
M Stya and D Axelrod
We report the lateral mobility of extrajunctional acetylcholine receptors
(AChR), marked with fluorescently labeled alpha-bungarotoxin, on rat flexor
digitorum brevis single muscle fibers maintained in cell culture. Mobility
is measured by a modification of the fluorescence photobleaching recovery
technique. The denervated rat flexor digitorum brevis muscle fibers exhibit
a nonuniform distribution of AChR on their sarcolemmas. Diffusely
distributed AChR have an average diffusion coefficient of about 2.5 X
10(-11) cm2/sec, somewhat lower than that of diffusely distributed AChR on
embryonic rat myotubes in culture. Extrajunctional AChR aggregated into
small clusters (less than 20 microns) have an average diffusion coefficient
of about 5 X 10(-12) cm2/sec. Both the clustered and nonclustered
extrajunctional AChR have lateral mobilities several orders of magnitude
greater than that of junctional AChR.