Hyperpolarization slowly activates a potassium current in locust skeletal muscle.
An inward current activated by hyperpolarization, IK,H, was studied under voltage clamp in locust skeletal muscle. The dependence of its reversal potential on [K+]o and its insensitivity to changes in [Na+]o indicate that the underlying conductance is a K+ conductance. The instantaneous current-voltage (I-V)-relationship exhibits outward rectification. Activation and deactivation take seconds and have complex time courses. At 10 mM [K+]o activation seems to start at a voltage greater than or equal to 20 mV more positive than the resting potential (approximately -68 mV). Ba++ blocks IK,H strongly; so do Rb+ and Cs+, the latter in a voltage dependent manner. The slow inward current bears similarities to anomalous rectifiers as well as to mixed, hyperpolarization-activated K+/Na+ currents in other tissues.
Zittlau
K E
KE
Institut für Normale und Pathologische Physiology, Philipps-Universität Marburg, Federal Republic of Germany.
Walther
C
C
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D006110:Grasshoppers; D007700:Kinetics; D008564:Membrane Potentials; D009132:Muscles / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000494:pharmacology
D002586:Cesium; D001464:Barium; D012413:Rubidium; D011188:Potassium