The Effect of Anesthetic Agents on Skeletal Muscle Membrane

Abstract

Summary. The action of pentobarbital sodium on neuromuscular transmission and the effects of pentobarbital, urethan, chloral hydrate, chloralose, paraldehyde and tribromethanol on skeletal muscle excitability has been investigated with the intracellular micro‐electrode technique in the isolated sartorius nerve‐muscle preparation of the frog. Pentobarbital sodium blocked neuromuscular transmission by rendering the end‐plate “receptors” unreactive to the depolarizing effect of acetylcholine. All agents caused an increase in the electric “threshold” of the muscle membrane and reduced or abolished the action potential. The rate of rise of an action potential was decreased by all agents. These effects occurred without significant changes in the resting membrane potential of the muscle fibre and without a decrease in the transverse electric resistance of the muscle membrane. On the basis of the ionic hypothesis for electric activity in nerve and muscle (H odgkin and K atz 1949). it is suggested that these effects on the membrane “threshold” and on the action potential are due to a reduction of the selective sodium conductance change caused by an inactivation of the “sodium carrying mechanism” in the muscle membrane. A close relationship was observed between the hypnotic dose in the intact frog and the concentration of the respective agent that caused a reduction of the selective sodium conductance change in the frog skeletal muscle membrane.