DOPA decarboxylase (aromatic L-amino acid decarboxylase, AADC, DDC) catalyzes the second reaction in the biosynthesis of catecholamines and serotonin (Waymire and Haycock, 2002, Berry et al., 1996, Haycock et al., 2003). It is also involved in the biosynthesis of trace amines. DDC antibodies can therefore be used as markers for dopaminergic, noradrenergic and serotonergic neurons in a variety of applications including depression, schizophrenia, Parkinson’s disease and drug abuse (Kish et al., 2001, Zhu et al., 2000, Zhu et al., 1999). Anti-DOPA Decarboxylase Western blot of 5 (g of bovine adrenal medulla lysate showing specific immunolabeling of the ~55k DOPA decarboxylase protein.