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Inward rectifier K+ currents in smooth muscle cells from rat resistance-sized cerebral arteries.
Quayle J, McCarron J, Brayden J, Nelson MT
American Journal of Physiology-Cell Physiology. 1993;265( 5 Pt 1):C1363-70.
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Abstract
Inward rectifier K+ channels have been implicated in the control of membrane potential and external K(+)-induced dilations of small cerebral arteries. In the present study, whole cell K+ currents through the inward rectifier K+ channel were measured in single smooth muscle cells isolated from the posterior cerebral artery of Wistar-Kyoto rats. The whole cell K+ current-voltage relationship showed inward rectification. Inward currents were recorded negative to the K+ equilibrium potential, whereas outward currents were small. When extracellular K+ was elevated, the zero current potential shifted to the new K+ equilibrium potential, and the conductance of the inward current increased. Inward currents were reduced by external barium or cesium. Inhibition by barium and cesium increased with membrane hyperpolarization. The half-inhibition constant for barium was 2.2 microM at -60 mV, increasing e-fold for a 23-mV depolarization. We provide the first direct measurements of inward rectifier K+ currents in single smooth muscle cells and show that external barium ions are effective blockers of these currents.
Keyword(s)
Animals; Charybdotoxin; Female; Kinetics; Rats; Rats, Inbred WKY; drug effects: Cerebral Arteries; drug effects: Membrane Potentials; drug effects: Muscle, Smooth, Vascular; drug effects: Potassium Channels; metabolism: Potassium; pharmacology: 4-Aminopyridine; pharmacology: Barium; pharmacology: Glyburide; pharmacology: Scorpion Venoms