Haemodynamic studies with impromidine in anaesthetised cats and rats

We measured in anaesthetised cats and rats the haemodynamic responses to intravenous infusions of the histamine H2-receptor agonist impromidine. In both species, an impromidine infusion rate that decreased total peripheral vascular resistance and increased left ventricular output without lowering blood pressure was identified. In the cat, impromidine, at infusion rates that did not lower blood pressure, increased coronary, gastric, and skeletal muscle blood flow; in the rat, it increased coronary, gastric, and hepatic arterial blood flow. At a higher infusion rate, which reduced total peripheral vascular resistance sufficiently to lower blood pressure in the cat, impromidine increased coronary, gastric, and skeletal muscle blood flow and decreased renal, cerebral, and cutaneous flow. In the rat, the higher impromidine infusion rate led to increases in coronary, gastric, hepatic arterial, and renal blood flow and decreased cutaneous flow. These results suggest that the complementary vasodilator and inotropic actions of impromidine may be of value in the treatment of severe cardiac failure.