A synthetic precursor and prodrug of norepinephrine; increases norepinephrine levels in the rat heart following intraperitoneal administration and in the brain following intracerebroventricular administration at doses of 125 and 100 μg/animal, respectively; increases arterial pressure and mesenteric arterial resistance in rats with ligated portal vein or biliary ducts when used at doses of 25-50 mg/kg; crosses the blood brain barrier but works through a peripheral mechanism