Effect of Dichloroisoproterenol on Vascular Responses to Catecholamines in Man*

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Abstract
Simultaneous injections of epinephrlne (2 doses, 0.06 to 0.25 lig) and of isoproterenol (2 doses, 0.06 to 0.25 p.g) were made into femoral arteries of 10 subjects. The 4 pairs of injections were given in random order before and after simultaneous infusions of DCI into the left (experimental side) and saline into the right (control side) femoral artery. Blood flow through both calves was measured with plethys-mographs. The results suggest that DCI selectively blocks adrenergic vasodilator receptors in blood vessels of the calf of man. Isoproterenol and epinephrlne appear equipotent in their action on these receptors. The vasodilator action of histamine was unaffected by the antagonist, DCI. Vasoconstriction followed the vasodilator responses to epinephrine, isoproterenol, and histamine. The constrictor action of epinephrine, isoproterenol, and histamine was reduced by DCI, but that of norepinephrine was not.