Posttetanic Changes in the Human Neuromuscular System

¹ From the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland

Percutaneous stimulation of the human ulnar nerve produced muscle action potentials from the adductor pollicis muscle and twitch tension responses from thumb adduction. With increase in the stimulus strength, approximately proportional increases were found in the height of the muscle action potential and twitch tension. Tetanization can produce a long lasting potentiation of twitch tension which is accompanied by either increased, decreased or unchanged amplitude of muscle action potentials. With increase in the duration, frequency or intensity of the tetanus, an additional effect producing decreased muscle action potentials and twitch tension responses appeared, particularly at 20–30 seconds after the cessation of the tetanus. Possible mechanisms and sites of action of posttetanic potentiation in the neuromuscular system are mentioned.

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