Non-selective cation channels in cerebrovascular smooth muscle cells of adult rats.
Inside-out patch clamp recordings have revealed the presence of a novel, large conductance channel of the non-selective, cation permeable type in smooth muscle cells dispersed from the cerebral arteries of adult rats. In physiologically appropriate ionic gradients, current flow in these channels reversed polarity at a membrane potential of about -42 mV. Single channel conductance in symmetrical 140 mM K+ salines was 211 pS. The channel was permeable to both K+ and Na+, with a ratio PNa/PK = 0.15, while Cl- was effectively impermeant. Calcium ions were weakly permeant (PCa/PK = 0.03, PCa/PNa = 0.20). Channel open probability increased with membrane depolarization and was weakly dependent on the concentration of free intracellular Ca2+. This channel would contribute outward membrane current at potentials more positive than about -42 mV. In concert with outward potassium currents, it may serve to limit membrane depolarization during action potential activity in cerebrovascular smooth muscle cells.
Mathers
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DA
Department of Physiology, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Zhang
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X
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000378:metabolism*; D007473:Ion Channels / Q000032:analysis*; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism
D007473:Ion Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium