Post-Tetanic Potentiation Before and During Ischemia in Intact Human Skeletal Muscle

Abstract

Potentiation of single twitch tension was demonstrated in intact human adductor pollicis brevis muscle for as long as 10 min. after tetanic stimulation (30/sec. for 1 sec.) of the ulnar nerve. This potentiation of twitch tension was accompanied by a decrease in the latent period of contraction and a slowing followed by a speeding of contraction but was unassociated with changes in the muscle action potential. Local circulatory arrest for 10 min. abolished all post-tetanic phenomena but did no alter nerve conduction, neuromuscular transmission and muscle contraction as judged by the pre-and post-tetanus twitches before and during ischemia. It appeared that the failure of post-tetanic potentiation during ischemia was not due to: (a) a decrease in the number of active fibers, (b) changes in initial tension, (c) depression of monosynaptic and stretch reflexes, (d) a decrease in muscle temp., and (e) depression of nerve conduction or neuromuscular transmission. Various factors which could account for the failure of the post-tetanic phenomena were discussed and it was suggested that a study of the events following tetanus would be useful in various neuromuscular disorder.