Effect of procaine on asphyxial rigidity

Abstract

Procaine (0.2–0.5%) was applied to the motor nerve of the gastrocnemiussoleus muscle of cats showing either “secondary” or “late” tone after asphysiation of the cord for appropriate periods of time. The drug tended to abolish the responses both to sinusoidal slow and fast (0.2–2 cycle/sec) stretch of the muscle before the muscle action potentials elicited by a single shock to the sciatic nerve started to decline. Although secondary tone in contrast to the late tone is characterized by considerable γ-efferent activity, both forms of asphyxial rigidity were similarly affected by procaine. It was, therefore, postulated that, in addition to the selective effect of procaine on the γ-efferents, this local anesthetic also affects the transmission of high frequency impulse trains in the Ia fibers, which represent the sensory input for the myotatic reflex underlying the response of the muscle to stretch. Evidence was obtained that in the concentrations and time of application used to affect the stretch responses procaine impedes the transmission of high frequency trains of impulses.