Single channel recordings from calcium-activated potassium channels in cultured rat muscle

Single channel recordings from cultured rat skeletal muscle have revealed a large conductance (230 pS) channel with a high selectivity for K+ over Na+. In excised patches of membrane, the probability of channel opening is sensitive to micromolar concentrations of calcium ions at the intracellular surface of the patch. Channel openings appear grouped together into bursts whose duration increases with Ca2+ and membrane depolarization. Statistical analysis of the individual open times during each burst showed that there are two distinct open states of similar conductance but dissimilar average lifetimes. These channels might contribute to a macroscopic calcium-activated potassium conductance in rat skeletal muscle and other preparations.