Abstract
1) M. rectus abdominalis (rectus abd. hereunder) of frog is frequently used for the calculation of acetylcholine and choline-esterase. To reveal the basic mechanisms of this method for acetylcholine and choline-esterase, the present experiments were undertaken.
2) When the rectus abd. of frog was immersed in Ringer's solution containing acetylcholine at various concentrations, it contracted slowly, and its contraction heights were found proportional to the acetylcholine concentrations. The relation between the contraction height and acetylcholine concentration was lineal, allowing to error.
3) Acetylcholine acted upon the rectus abd. to evoke respetitive spike potentials at the beginning of its action, thereafter fell into silence, but the muscle contraction still continued.
4) At heigher concentrations of acetylcholine, repetitive spike potentials appeared more frequently, and their duration was prolonged.
5) Such contractions of rectus abd. caused by acetylcholine was supposed to be “fibrilare Zuckungen”. Acetylcholine was supposed to act, in such cases, on the end plates of the nerve fibres in the muscle.
6) But, there appeared another kind of contraction accompanying no spike potential caused by the action of acetylcholine. This type of contraction was different from the above mentioned one. Such contraction was probably evoked by the direct action of acetylcholine on the sarcoplasma, therefore, it was contracture by its nature.
7) The authors regarded these two phenomena observed in the muscle fibres as dissimilar ; one generated “fibrilare Zuckungen”, the other “contracture”.
8) The fact was elucidated that for the calculation of choline-esterase and acetylcholine, the rectus abd. of frog is utilizable with sufficient accuracy.
