[Electrogenesis and contraction of smooth muscle taenia coli kept in a solution with elevated concentration of potassium ions]

Abstract

Experiments performed on smooth muscle strips of guinea-pig taenia coli in high-potassium solution using sucrose-gap method revealed that phasic and tonic components of contractile response following potassium depolarization were due to influx into the cells of Ca++ ions from extracellular solution through two types of voltage-dependent Ca channels: the fast inactivated and the slow noninactivated those. After cessation of the fast Ca channel inactivation with anodal current the membrane recovers its ability to generate spontaneous or evoked AP depending on repolarization level. Under these conditions AP generation can also occur in Ca-free and Na-free solutions due to regenerative process of K-channel activation.