norepinephrine

any agent that causes a narrowing of an opening of a blood vessel: cold or stress or nicotine or epinephrine or norepinephrine or angiotensin or vasopressin or certain drugs; maintains or increases blood pressure

a monoamine that is functionally important in neural transmission

any of a group of chemicals including epinephrine and norepinephrine that are produced in the medulla of the adrenal gland