Ethanol effects on muscle spindle afferent activity and spinal reflexes

CM Lathers and CM Smith

The effects of ethanol on muscle spindle afferent activity and on the mono- and polysynaptic reflexes were examined in cats. Ethanol was administered incrementally as intravenous infusions of 0.7 g/kg of ethanol 30 minutes apart; mean arterial blood alcohol concentrations reached 30 minutes after the first and fourth infusions were 1.1 and 3.8 mg/ml, respectively. Ethanol produced modest, dose-related increases in the afferent activity from muscle spindles in spinal- and pentobarbital-anesthetized cats. Mean phasic and static discharge frequencies were both increased approximately 10 impulses/sec after infusions of a total of 2.8 g/kg. In unanesthetized animals, comparable blood levels of ethanol were associated with mild to marked motor incoordination. The mean amplitudes of the mono- and polysnaptic reflexes in spinal animals, elicited with supramaximal single shocks to the muscle nerve, were depressed to 92 and 84% of control levels, respectively, after 0.7 g/kg and continued to fall to 50 and 60% of control levels after 2.8 g/kg of ethanol. Ethanol failed to depress preferentially polysynaptic reflexes. It is concluded that the spindle afferent excitation was involved in the motor effects of ethanol but that it was insufficient to explain fully the skeletomotor alterations produced by ethanol; rather, ethanol actions at peripheral and spinal and, perhaps, supraspinal sites all appear to be involved in ethanol- induced impairment of motor function.

Volume 197, Issue 1, pp. 126-134, 04/01/1976
Copyright © 1976 by American Society for Pharmacology and Experimental Therapeutics