The Suppression of the Late After-Potential in Rubidium-Containing Frog Muscle Fibers

Abstract

The late after-potential that follows trains of impulses in frog muscle fibers is virtually absent when most of the intracellular K is replaced by Rb and the muscle is immersed in Rb-containing Ringer''s fluid. Its amplitude is also reduced in freshly dissected, K-containing muscle fibers that are immersed directly in Rb-Ringer''s fluid. These findings are discussed in terms of the model for muscle membrane of Adrian and Freygang (1962 a, b) and in relation to the report of Adrian (1964) that Rb-containing muscle fibers do not exhibit the variations in K permeability as a function of membrane potential that are found in fibers with normal intracellular K concentration immersed in Ringer''s fluid.