Reaction of blood pressure and mesenteric blood flow to an infusion of biogenic amines in rats: influence of irradiation and alpha blockers.

The reaction of systemic blood pressure and mesenteric blood flow to an infusion of different biogenic amines was determined in controls and in lethally (8 Gy) X-irradiated rats. The influence of the alpha blocker phenoxybenzamine on these reactions was also investigated. Changes in blood pressure and flow response similar to, but less marked than, those seen earlier after a supralethal (20 Gy) exposure were detected 3 and 7 days after irradiation. These observations as well as the consequences of alpha blockade suggest that the reactivity of alpha receptors in blood vessels is reduced after irradiation, and that the function of the heart is impaired.