THE SLOW COMPONENTS OF THE ELECTROGRAM OF STRIATED MUSCLE

Abstract

The electric responses of circulated cat''s muscles (mainly sartorius) were recorded with direct-coupled amplification together with the mechanical effects of indirect stimulation. The electrogram of normal muscles is complex; a spike potential is followed by slow potential changes. Repetitive stimulation results in summation of some of the slow components. Veratrine increases the negative slow components of the electrogram in addition to other striking effects. Yohimbine may similarly increase the negative residual potentials without any significant change of the mechanical reactions. The electric responses of denervated muscles to injns. of acetylcholine include several slow components. The following systematization of muscle potentials is suggested: excitation potentials, which precede conduction (e.g., the end-plate potential); conduction potentials (the spike and the afterpotentials); contraction potentials (those associated with the development of tension and with the corresponding recovery processes). None of the potentials recorded was invariably correlated in time with contraction. When such a correlation appeared the potential was relatively positive. It is inferred that one of the contraction potentials may be positive. An independent variation of the residual negativity and of contraction is produced by veratrine. It is inferred that this negativity denotes an afterpotential. The spike potential amplitude and tension may also vary independently.