REGIONAL BLOOD FLOW CHANGES DURING NOREPINEPHRINE, TYRAMINE AND METHOXAMINE INFUSIONS IN THE UNANESTHETIZED RHESUS MONKEY

¹ Division of Clinical Pharmacology and Cardiovascular Research Institute, University of California San Francisco Medical Center, San Francisco, California

Simultaneous measurements of regional blood flow and resistaisce were made in unanesthetized monkeys with the radioactive microsphere method before and after 20- to 40-minute i.v. infusions of norepinephrine, tymamine and methoxamine. Equipressor doses of norepinepisrine and tyramine caused redistribution of the cardiac output with increased vascular resistance in brain, skin, gastrointestinal tract. liver and bone but resistance in heart and skeletal muscle was unaltered. The major difference was in adipose tissue in which norepinephrine produced increased blood flow and vasodilatation whereas tyramine caused vasoconstriction and a reduction in blood flow. Metisoxamine, on the other hand, which has solely alpha adrenergic receptor stimulating properties evoked a widespread, more or less uniform, increase in vascular resistance wit no significant changes in the distribution of cardiac output.