ACETYLCHOLINE RELEASE FROM MOTOR NERVE ENDINGS

Publisher Summary This chapter describes acetylcholine release from motor nerve endings. The miniature potentials are caused by release of ACh from the nerve endings. The frequency of the discharge can be controlled, rapidly, and over a wide range, by passing electric current through the terminal part of the motor axon, and the miniature potentials disappear after denervation at a time when the nerve endings degenerate and they are abolished by local botulinum poisoning at a time when the release of ACh stops. In denervated frog muscle, the disappearance of the spontaneous discharge is not permanent, but is followed one or two weeks later by a resumption of activity on a much reduced scale. By contrast, in denervated mammalian muscle, a resumption of miniature potentials is only very rarely observed. Electron-microscopic evidence suggests that the reactivation depends upon the development of close contact between the terminal Schwann cells and the end-plate.