An electrophysiological analysis of the true pessimum made on the neuromuscular apparatus of adult animals

Summary

An electrophysiological method was used for analyzing the mechanism of inhibition in adult dogs which I. A. Arshavskii has described as the true pessimum. The maximum value of the action potential was determined when the nerve was stimulated at a frequency of 40/sec. With further increase of the stimulus frequency the amplitude of the action potential decreased, and disappeared completely at a stimulus frequency of 80–90/sec. The nerve continued to reproduce the action potential unchanged in amplitude not only at this frequency but at others much higher. The true pessimum condition is due to blockade of the nerve impulse at the myoneural junction; it is characterized by an accumulation of energy reserves in the muscle itself, which results in the posttetanic activation phenomenon. This phenomenon consists in a considerable increase in the amplitude of the muscle action potential over its initial value.