POST-TETANIC POTENTIATION AND SUPPRESSION IN MUSCLE

Abstract

Muscle and nerve action-potentials and twitch-tension were observed simultaneously in the isolated frog sciatic-gastrocnemius prep. Potentiation was not obtained in the completely curarized prep. by direct stimulation. It was obtained in the partly curarized prep. The results of normal fatigue and curare were similar. Potentiation was obtained after the adm. of depressing doses of K. K never enhanced the potentiating effect of tetani. The muscle action-potential accompanying the potentiated twitch was greater than that accompanying the twitch preceding the conditioning tetanus. The nerve action-potential after the tetanus was usually decreased. Suppression of the muscle response after a prolonged tetanus was due to a decrease in the number of nerve fibers responding to the test-shock. It was concluded that potentiation was due to the facilitating effect of blocked nerve impulses. It was suggested that since others have shown the inadequacy of the chemical theory of neuro-muscular transmission in explaining these events, a chemical explanation of post-tetanic potentiation is also inadequate.