Adrenergic Stimulation of Depolarized Arterial Muscle

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Abstract
The excitation-contraction reactions of arterial smooth muscle to epinephrine and electrical current were studied in isolated segments of canine small-caliber arteries by means of a constant-flow perfusion technique. The arterial pressure elevations produced by the contractile responses of the smooth muscle to epinephrine were equally large, reproducible, and specifically antagonized by piperoxan whether or not the artery had been depolarized by isosmotic solutions rich in potassium and devoid of sodium. Responses to electrical current were impaired by potassium depolarization. In the potassium-depolarized vascular smooth muscle, relaxation of the induced contractions was moderately delayed.