Aromatic Amino Acids and Modification of Parkinsonism

THE known biochemical abnormalities in Parkinson's disease consist of a decrease of melanin pigment in the substantia nigra1 , 2 and a decrease of some biogenic amines in the substantia nigra and the corpus striatum.3 These 2 defects might be interrelated, as suggested by the fact that in both melanocytes4 and sympathetic cells5 tyrosine is hydroxylated to dihydroxyphenylalanine, a common precursor in the synthesis of both melanin and catecholamines. Furthermore, both melanocytes and sympathetic cells originate from the neural crest.6 It was suggested earlier7 , 8 that the interrelations between melanogenesis and extrapyramidal disease might be of fundamental importance. It was noted that chronic . . .