Effect of acetylcholine and vagostigmine on muscle and nerve of frog.

1) The effect of acetylcholine and vagostigmine on isolated muscle of frog and nerve-muscle preparations, with single induction shocks was studied. 2) Direct application of acetylcholine or vagostigmine to the muscle preparation produces a depressant action on the excitability as well as on the shortening height of the maximum contraction. The effects are more marked when the two drugs are applied simultaneously or successively than when applied separately. 3) Direct application of acetylcholine or vagostigmine to the nervous portion of the nerve-muscle preparation also produces a slight depressant action on the excitability of muscle to indirect stimulation applied to the nerve. 4) The applicability of the chemical transmission theory to amphibian muscles was discussed.