Inward rectifier K+ currents in smooth muscle cells from rat resistance-sized cerebral arteries.
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.
Quayle
J M
JM
Department of Pharmacology, Medical Research Facility, University of Vermont, Colchester 05446.
McCarron
J G
JG
Brayden
J E
JE
Nelson
M T
MT
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology*; D018999:Charybdotoxin; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D012604:Scorpion Venoms / Q000494:pharmacology
D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D001464:Barium; D015761:4-Aminopyridine; D011188:Potassium; D005905:Glyburide