Abstract

The depolarizing effects of acetyicholine, choline and carbamyicholine at the motor end-plate and in end-plate-free regions of frog sartorius muscles have been Studied in cesium Ringer's solution, in extension of earlier work in potassium Ringer's solution. The conclusion from previous studies in potassium Ringer's that two different quaternary ammonium ion-sensitive systems are operating in the muscle membrane is supported by the membrane responses in cesium Ringer's. No significant difference was seen in the response of the motor end-plate receptor in the two Ringer's solutions, but the increased stability of the end-plate-free region depolarization in cesium Ringer's suggests a significant change in quaternary ammonium ion binding characteristics of the conductance control system in this region. The magnitude of depolarization was greater in cesium Ringer's than had been found in potassium Ringer's for all three drugs.