Non-selective cation channels in cerebrovascular smooth muscle cells of adult rats

摘要

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 impetmeant. 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.