EFFECTS OF ALCOHOLS AND ACETONE ON THE NEUROMUSCULAR JUNCTION OF FROG

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Abstract
The effects of alcohols and acetone on the neuromuscular junction of frog sartorius muscles were investigated by observing Ach potentials, epps [end-plate potentials] and mepps [miniature end-plate potentials] intracellularly. The amplitude of epps was increased in up to about 1.5% ethanol-Ringer''s solution and was decreased in more concentrated ethanol. In about 1.5% or more concentrated ethanol, the neuromuscular transmission was blocked completely by "all-or-none" reversibly. The amplitude of Ach potentials was increased in up to about 1% ethanol and was decreased when the concentration of alcohol was over about 1%. The effects of methanol and acetone on Ach potentials were approximately the same as that of ethanol. The amplitude of mepps was increased gradually in ethanol Ringer''s solutions as the concentration of alcohol increased. Even in 3% ethanol in which the neuromuscular transmission was blocked completely, many large miniature discharges could be observed. The frequency of mepps was increased dramatically in alcohol- and acetone-Ringer''s solutions, it was about 9 times original in 3% methanol, about 13 times original in 2.5% ethanol, about 10 times original in 1.5% n-propanol and about 6 times original in 2.5% acetone. Ach potentials, epps and mepps were prolonged markedly in alcohol and acetone-Ringer''s solutions. The effective resistance of the muscle membrane was decreased in ethanol-Ringer''s solution. It was about 88% original in 3% ethanol. Based on these results of the present experiments, the mechanisms of the neuromuscular transmission and the effects of alcohols and acetone on neuromuscular junction were discussed.

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