norepinephrine (NE) /nôr′epinef″rin/ , an adrenergic hormone (catecholamine) that acts to increase blood pressure by vasoconstriction but does not affect cardiac output. It is synthesized by the adrenal medulla, the peripheral sympathetic nerves, and the central nervous system. It is available as a drug, levarterenol, which is used to maintain the blood pressure in acute hypotension secondary to trauma, heart disease, or vascular collapse.