RELATIVE SENSITIVITY OF SOME LARGE BLOOD VESSELS OF THE RABBIT TO SYMPATHOMIMETIC AMINES

¹ Department of Pharmacology, UCLA Center for Health Sciences, Los Angeles, California

The characteristics of the responses of helical strips of rabbit thoracic aorta, pulmonary and anterior mesenteric arteries and inferior vena cava to a series of sympathomimetic amines have been measured. The sensitivity of the anterior mesenteric artery and inferior vena cava, but not of the pulmonary artery, relative to that of the aorta, varied with amine structure. Substitution in the -carbon position of l-norepinephrine was responsible for some of the greatest changes in relative potency of the tested compounds. Alteration in structure had no effect on the slope of the dose-response curves. Evidence was obtained with dichloroisoproterenol that variation in the relative potency of the various amines on the different vessels was not the result of a varying population of alpha and beta adrenergic receptors in these vessels. This study demonstrates that the excitatory adrenergic receptors in vessels of similar size and function are not uniform.