Properties of single potassium channels in vesicles formed from the sarcolemma of frog skeletal muscle

• Published in: The Journal of physiology Vol. 364; no. 1; pp. 339 - 358
• Main Authors: Standen, N B, Stanfield, P R, Ward, T A
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01-07-1985; Blackwell
• Subjects: Action Potentials - drug effects; Animals; Anura; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Ion Channels - physiology; membrane vesicles; potassium; Potassium - physiology; Probability; Rana; Rana temporaria; sarcolemma; Sarcolemma - ultrastructure; skeletal muscle; Striated muscle. Tendons; Tetraethylammonium; Tetraethylammonium Compounds - pharmacology; Time Factors; Vertebrates: osteoarticular system, musculoskeletal system; Sarcolemma; Vertebrata; Frog; Amphibia; Electrophysiology; Salientia; Membrane channel; Striated muscle; Potassium
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1985.sp015749

The patch-clamp method was used to study unitary delayed rectifier K+ channels in large vesicles formed from the membrane
of frog skeletal muscle. Channels were activated by depolarizing pulses. Single-channel conductance was about 15 pS in physiological
[K+]o and was doubled by raising [K+]o to 120 mM. TEA+ caused an apparent reduction in single-channel current, which we attribute
to a rapid block. When depolarizations were repeated at brief intervals, records with and without channel openings were ordered
non-randomly, providing evidence for a slow process which was probably inactivation. In multichannel patches the relation
between variance and mean current, binomial analysis, and the distribution of times for single and double openings were all
consistent with channels behaving independently. Open times were distributed exponentially. Mean open time, tau o, increased
with depolarization so that 1/tau o was an exponential function of voltage. First latency histograms peaked at times later
than zero and could not be fitted by a scheme having only two closed states. Channel openings occurred in bursts and closed
time histograms could be fitted by the sum of three exponentials. Our results imply a scheme with at least three closed states,
an open and an inactivated state.