Comparative effects of the alpha-adrenoceptor agonists noradrenaline, phenylephrine and clonidine in the human saphenous vein in vivo and in vitro
The alpha-adrenoceptor-mediated contractile effects of noradrenaline (alpha 1 + alpha 2), phenylephrine (alpha 1) and clonidine (alpha 2) on human saphenous veins were investigated in vivo and in vitro. By infusion (0.3 ml min-1) of the drugs (increasing concentrations in the infused solution) into distended (40 mmHg) saphenous veins in six healthy subjects, local vasoconstriction was induced, mea