The stimulation of nerve-endings in muscle and the theory of receptive substances

Abstract

Langley has shown that the stimulating action of nicotine upon muscle is prevented by curare and that this antagonism is exhibited also in muscles in which the nerve fibers have been removed by degeneration. This and other facts have led him to formulate the hypothesis of special receptive substances present in the muscle upon which these drugs and other chemical stimuli exert their action, and furthermore he ventures the generalization, in contradiction of the usual belief, that “in no case do chemical substances have a special action on nerve-endings.”

The series of experiments here reported were made at the suggestion of Dr. J. W. Warren to test the above hypothesis. The gastrocnemius muscle of the frog was used and its reactions were studied after immersion in solutions of sodium sulphocyanide and potassium sulphocyanide. The following results were obtained.

1. Action of potassium sulphocyanide.—This salt was used in hypertonic solutions (2 per cent. KCNS made up in a Ringer's mixture) and in isotonic solutions (1 per cent. KCNS in water). In both cases solutions of this salt caused an immediate rapid primary contraction followed by a prolonged contracture. This effect was not removed by the action of curare nor by the degeneration of the motor nerve fibers. It was obtained also by the action of other potassium salts, e. g., potassium chloride—and must be considered as an instance of the “potassium contraction” described by other authors. The potassium ions may act upon the supposed receptive substance, but evidently their effect does not depend upon the presence of the nerve terminals.

2. Action of sodium sulphocyanide.—This salt was used also in hypertonic and isotonic solutions as in the case of the potassium sulphocyanide.