Effects of Small Oral Doses of Reserpine on Vascular

Abstract

Experiments were done to see if reserpine, in small oral doses, alters the responses to tyramine and norepinephrine in man. Each of seven normotensive subjects was studied on three occasions. The first and third sessions served as pre- and post-treatment control sessions; the second session was held after oral administration of reserpine (0.25 to 1 mg. per day) for 2 weeks. Blood pressure was measured with a sphygmomanometer, and forearm blood flow was measured with a water plethysmograph. Reserpine reduced resting blood pressure and heart rate but forearm blood flow did not change. The pressor, forearm vasoconstrictor, and bradycrotic actions of intravenous tyramine were suppressed by reserpine, but the pressor, vasoconstrictor, and bradycrotic actions of three intravenous doses of norepinephrine were not augmented significantly. The results indicate that oral administration of small doses of reserpine may cause depletion of endogenous catecholamines in man as suggested by the suppressed response to tyramine. The decreased response to tyramine was not accompanied by hypersensitivity to exogenous norepinephrine. In equipressor doses norepinephrine produced greater forearm vasoconstriction and more reflex bradycardia than did tyramine.