Biochemicals are in plain text and processes in italics. The colored rectangles represent (blue) vesicles and two cytoplasmic compartments, one involving processes proximal to cytoplasmic dopamine (banana color) and the other distal to cytoplasmic dopamine production (pink). Abbreviations: ALDH=aldehyde dehydrogenase; AR=aldehyde/aldose reductase; COMT=catechol-O-methyltransferase; Cys-DOPA=5-S-cysteinyldopa; Cys-DA=5-S-cysteinyldopamine; DA=dopamine; DHPG=3,4-dihydroxyphenylglycol; DOPA=3,4-dihydroxyphenylalanine; DOPAL=3,4-dihydroxyphenylacetaldehyde; DOPEGAL=3,4-dihydroxyphenyglycolaldehyde; HVA=homovanillic acid; LAAAD=L-aromatic-amino-acid decarboxylase; MAO=monoamine oxidase; MHPG=3-methoxy-4-hydroxyphenylglycol; NE=norepinephrine; Ox.=spontaneous oxidation; TH=tyrosine hydroxylase; VMAT=vesicular monoamine transporter.