Definition of Vasoconstrictor:

A nerve or agent that causes constriction of blood vessels by promoting the contracton of vascular smooth muscle [ORWJr]. Also called vasopressor. Cold, fear, stress, and nicotine are common exogenous vasoconstrictors. Internally secreted epinephrine and norepinephrine cause blood vessels to contract by stimulating alpha-adrenergic receptors on the vascular smooth muscle. Other endogenous vasoconstrictors are angiotensin, which is formed in the blood through the action of renin, and antidiuretic hormone, which is secreted by the pituitary. Alpha-adrenergic sympathomimetic drugs also cause vasoconstriction, and several of these agents are used for this action in maintaining blood pressure during anesthesia and in treating pronounced hypotension resulting from hemorrhage, myocardial infarction, septicemia, sympathectomy, or drug reactions. Among these therapeutic agents are phenylephrine, metaraminol, and norepinephrine [Mosby2009].

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