External barium and cesium effectively blocked inward rectifier K+ currents in single smooth muscle cells from rat cerebral arteries, with barium showing a half-inhibition constant of 2.2 microM at -60 mV.
This study provides the first direct measurements of inward rectifier K+ currents in single smooth muscle cells from rat cerebral arteries and demonstrates their effective blockade by external barium ions.
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 et al. (Mon,) reported a other. External barium or cesium was evaluated on Inward rectifier K+ currents. External barium and cesium effectively blocked inward rectifier K+ currents in single smooth muscle cells from rat cerebral arteries, with barium showing a half-inhibition constant of 2.2 microM at -60 mV.