Direct cardiac effects of dopamine.

• Dopamine (3,4 dihydroxyphenylethylamine), a biochemical precursor of levarterenol and epinephrine, has been shown in previous studies in intact animals to be pressor in the eat, depressor in the rabbit and guinea pig, and to have a variable, but predominantly pressor effect in the intact dog. Dopamine has been shown by Fowler, Shabetai, and Holmes to produce contraction of the rabbit aortic strip in amounts above 4 fig. It has been reported by Horwitz, Goldberg, and Sjoerdsma that the effects of intravenous infusions of dopamine in man were significantly different from those of levarterenol, for dopamine increased chiefly systolic blood pressure, whereas levarterenol increased both systolic and diastolic pressure. Such results suggest that dopamine produces an elevation in blood pressure by increasing the cardiac output rather than by causing peripheral vosocoustriction.