Effects of Ethanol on the Membrane Potential and Membrane Resistance of Frog Muscle Fibres

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Abstract
The effects of ethanol on the membrane potential and membrane resistance of frog muscle fibres in vitro were studied by means of intracellular microelectrode technique. By continuous recording of the membrane potential level from one fibre, as well as by consecutive recordings from different fibres, the time course of the potential changes induced by different concentrations of ethanol was followed for periods of up to one hour. At the lowest concentrations used, 0.05 and 0.1 M, a depolarization, although slow and sometimes irregular, could usually be demonstrated. At a concentration equal to or higher than 0.2 M, a marked lowering of the membrane potential value was regularly observed. The depolarization rate increased with higher ethanol content, a typical result being a 15 per cent reduction of the initial membrane potential value after 15 min of exposure to 1.0 M ethanol. Reversal of the membrane potential changes after the ethanol had been washed out from the muscle bath was also demonstrated. Determinations of the voltage‐current relation of the muscle fibre, either by square pulse analysis or by direct recording of voltage‐current curves, revealed a gradual lowering of the membrane resistance, the effect increasing with the ethanol concentration from 0.2 to 1.0 M; at lower concentrations the changes in membrane resistance were within the normal variations found in untreated muscle.

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