Effect of serotonin (5-hydroxytryptamine) on the systemic and coronary vascular bed of the dog

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Abstract
Dogs were anesthetized with morphine and Dial-urethane-Nembutal. Cardiac output (Fick) and coronary blood flow (N2O Fick) were measured before and after the mechanical infusion of 20 µg/kg/ min. of serotonin over a period of 25 minutes. The results showed an increase in heart rate, pulmonary arterial pressure and right ventricular work. Systemic blood pressure and resistance were reduced. Coronary blood flow increased by 79%, with an increase of coronary sinus oxygen content of 3.3 vol. %. Cardiac O2 consumption and CO2 production increased. Mechanical efficiency of the left ventricle fell by 3%. Serotonin appears to act as a powerful coronary vasodilator, increasing the oxygen supply to the myocardium without increasing left ventricular work.