[Mechanism of the relaxant action of noradrenaline on coronary artery smooth muscle cells]

Abstract

Electrical and contractile activity of smooth muscle cells (SMC) of bovine coronary arteries was examined by the double sucrose gap method. It was shown that, on the one hand, noradrenaline increased the potassium membrane permeability followed by hyperpolarization which led to the closing of potential-dependent show calcium channels and to the reduction of the transmembrane calcium ion influx. On the other hand, noradrenaline closed potential-dependent chemosensitive calcium channels that limited influx of extracellular calcium ions into SMC. Such a double-noradrenaline effect resulted in a considerable decrease of the concentration of intracellular calcium ions and in the falling of the basal tone of arterial SMC.