Physiological Significance of Post‐Tetanic Potentiation of the Spinal Monosynaptic Reflex

Abstract

Summary.Experiments were made on anesthetized, decerebrate and spinal cats. The spinal cord (lumbar segments) was de‐efferented, and one leg totally denervated except for one muscle which was left intact and investigated.1. After tetanization of the intact muscle nerve, its monosynaptic spinal reflex was potentiated (confirming LLOYD, 1949).2. Intense afferent activity from a muscle, produced by repetitive stretch or tetanic contraction of long duration, was not followed by post‐tetanic potentiation of its monosynaptic test reflex of perceptible magnitude.3. During post‐tetanic potentiation (a) the stretch reflex and “contraction reflex” were usually not altered, although sometimes the stretch reflex was moderately increased; (b) the afferent response to muscle stretch or contraction was not perceptibly decreased, except during a short period after the tetanus; (c) only the first few of the monosynaptic reflex responses to tetanic afferent stimulation were potentiated.4. The experimental result indicates (a) that post‐tetanic potentiation follows only after high‐frequency afferent firing, difficult to produce by physiological stimulation; (b) that, when produced by afferent tetanic stimulation, post‐tetanic potentiation is not of great quantitative importance for reflexes elicited by asynchronous or repetitive afferent firing.