Muscle activity decreases rate of degradation of alpha-bungarotoxin bound to extrajunctional acetylcholine receptors.

Abstract

DURING development of skeletal muscle, and after denervation or reinnervation of adult muscle, there are significant changes in the number of extrajunctional acetylcholine (ACh) receptors, measured both by sensitivity to ACh and by binding of α-125I-bungarotoxin (for review, see ref. 1). Muscle activity has been shown to be a major factor in controlling the level of extrajunctional receptors. Direct electrical stimulation of denervated muscle both in vivo and in vitro decreases the sensitivity of the extrajunctional membrane to ACh2–5, whereas chronic postsynaptic blockade of innervated muscle in vivo increases its sensitivity6,7. Muscle activity could alter the level of extrajunctional receptor by changing rates of synthesis or degradation of the receptor.