Vasodilation and aging evaluated in the isolated perfused rat mesenteric vascular bed: preliminary observations on the vascular pharmacology of dobutamine.

The influence of animal age of drug-induced vasodilation was investigated in the perfused rat mesentery constricted with norepinephrine. Responses to isoproterenol, a beta-receptor stimulant, decreased with increasing age. Also, there was a modest decline in the relaxation produced by papaverine. In contrast, dilation of the rat mesentery by acetylcholine, histamine, or nitroglycerin either did not change with age or the responses became somewhat larger. Dobutamine, a myocardial beta-receptor stimulant, produced a marked relaxation of the mesentery. A comparison of the action of isoproterenol and dobutamine revealed that isoproterenol stimulated vascular beta-receptors, whereas dobutamine relaxed the mesentery by antagonizing the tone produced by norepinephrine. The dilation resulting from the alpha-receptor-blocking action of dobutamine was unrelated to animal age.