HEMODYNAMIC EFFECTS OF SYSTEMIC AND CENTRAL ADMINISTRATION OF ALPHA-METHYLDOPA

  • 1 January 1978
    • journal article
    • research article
    • Vol. 205  (3) , 675-682
Abstract
Systemic and regional hemodynamic changes were measured in 5 restained, conscious rhesus monkeys [Macaca mulatta] before and after a 2 h i.v. infusion of 50 mg/kg of .alpha.-methyldopa and, in another group of 5 monkeys, 5-10 mg injected into a lateral cerebral ventricle. Both routes of administration evoked similar degrees of hypotension, bradycardia and decreased cardiac output, although the cerebral intraventricular (i.c.v.) injections had more immediate and long-lasting effects. Both groups had a similar pattern of changes in the redistribution of cardiac output and blood flow that lasted at least 4 h. Blood flow was maintained in the hepatic and renal arteries and decreased in skeletal muscle, heart, brain and skin. In contrast, i.c.v. injections of .alpha.-methyldopamine and .alpha.-methylnorepinephrine given at the same site evoked dose-related pressor responses that lasted for up 4 h. .alpha.-Methyldopa has important central action that inhibits sympathetic outflow, but that its hypotensive effect is either mediated only by endogenously formed metabolites or that its mechanism of action is not directly related to these metabolites at sites around the lateral and 3rd cerebral ventricles in the monkey.

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