Pulmonary and Systemic Vascular Response to Continuous Infusion of 5-Hydroxytryptamine (Serotonin) in the Dog

Abstract

The pulmonary and systemic vascular responses to continuous venous infusion of 5-hydroxytryptamine were studied in eight dogs. Chronic catheterization of the pulmonary artery, aorta, and in some animals, the left auricle, permitted repeated studies in the same animal. Infusion rates as low as 20 µg/kg/min. of serotonin creatinine sulfate resulted in a twofold increase of pulmonary arterial pressure. In 11 experiments with an infusion rate of 150 µg/kg/min. there was a 300% increase of mean pulmonary pressure, a 28% drop in systemic arterial mean pressure, and a 60% rise of cardiac output. Calculated pulmonary resistances markedly increased to 500% of control levels, but in contrast, systemic resistances decreased by 55%. 5-Hydroxytryptamine is a powerful vasoconstrictor of the pulmonary vessels and a vasodilator of peripheral vessels, when administered by continuous infusion, and these effects persist as long as the drug is administered. The possible role of 5-hydroxytryptamine in production of pulmonary hypertension in congenital heart disease is considered.