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(also noradrenaline, arterenol, 3,4-dihydroxyphenylethanolamine), a biologically active catecholamine. Norepinephrine has the following structure:
In animals and man, norepinephrine is in part produced by the chromaffin cells of the adrenal medulla, but it is mostly secreted by the adrenergic nerve elements of the sympathetic nervous system, where it serves as a chemical transmitter, or mediator substance, in nerve excitation. Judging by its action on the heart, blood vessels, smooth muscles, and carbohydrate metabolism, norepinephrine possesses the properties of hormones and is similar to its N-methyl derivative—adrenaline. The level of norepinephrine in the blood, organs, and excretions of the body is an indicator of the tone and reactivity of the sympathetic nervous system.
Norepinephrine can be produced synthetically. It is used in medicine to treat such conditions as low blood pressure, collapse, shock, and hemorrhage.