Is Acetylcholine the Trophic Neuromuscular Transmitter?

Abstract

THE IMMEDIATE effect of denervation of skeletal muscle is motor paralysis. Over the longer term, denervation leads to a series of alterations in the morphology, physiology, and metabolism of muscle which have been termed "atrophic."^1,2It is clear that the motor nerves alone supply the "trophic influence" which is capable of preventing these changes, while the sensory and sympathetic innervation play no significant role.^3-5The question of how the nerves exert this effect remains of paramount importance. The weight of present evidence suggests that neither conduction of motor nerve impulses nor mechanical work of muscle are the factors necessary to prevent denervation atrophy of skeletal muscle. Elimination of conducted nerve impulses by various experimental techniques^6-8fails to reproduce fully the effects of denervation, provided that the motor nerves remain anatomically and functionally connected to the muscle. Furthermore, relieving skeletal muscle of its work load (for example,