Time courses of late after-potentials following tetanus or single shock in skeletal muscle fibers.

Characteristics of the late after-potential (LAP) of amphibian skeletal muscle fibers were studied in low chloride solutions. The LAP elicited by tetanus was larger in magnitude and slower in its course than the LAP elicited by single spike. The results are in quantitative agreement with predictions based on the theory that the LAP is produced by a potassium accumulation in the transverse tubular system and its time course determined by a diffusion process of the potassium from the tubular lumen into the outside.