The term catecholamine refers to a group of substances with low molecular weight that contain a catechol nucleus (i.e., two hydroxyl ions, on the 3- and 4-positions) and an amine on the side chain (Fig. 1). The numbering system begins with the carbon adjacent to the side chain (with the first carbon atom called alpha, the second beta, etc.) and rotates counterclockwise within the phenol ring. Monoamine is an ambiguous term that applies to any aliphatic, aromatic, or heterocyclic compound in which a hydrogen atom has been replaced by an amine group. In the field of cerebral research, however, the term has been used to refer specifically to four substances found in the brain and the rest of the central nervous system: two primary amines, dopamine and noradrenaline; one secondary amine, adrenaline; and an indolealkylamine, serotonin. For the purpose of standardization, monoamine in this text will refer only to these four compounds.
KeywordsTyrosine Hydroxylase Monoamine Oxidase Nerve Ending Adrenal Medulla Tryptophan Hydroxylase
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