Effects of apamin on the outward potassium current of isolated frog skeletal muscle fibres

Abstract
The effect of apamin, a polypeptidic toxin from bee venom which is a specific blocker of certain Ca2+-dependent K+ channels, has been tested (50–100nM) on voltage clamped single skeletal muscle fibres of the frog. The results have shown the existence of an inhibitory effect of the toxin on the slow outward K+ current which suggests the existence of a Ca2+-sensitive component of the slow K+ permeability in the plasma membrane of the frog muscle fibre.