A major metabolite of l-dopa in man and animals, which has a considerably longer biological half-life than l-dopa: Pletscher et al., Brain Res. 4, 106 (1967); Bartholini, Pletscher, J. Pharmacol. Exp. Ther. 161, 14 (1968); Kuruma et al., Eur. J. Pharmacol. 10, 189 (1970). Proposed as a precursor of dopamine via its partial demethylation in the organism: Bartholini et al., Nature 230, 533 (l971); Chalmers et al., Br. J. Pharmacol. 43, 455P (1971); Bartholini et al., Life Sci. 14, 323 (1974). See also Carlsson, Waldeck, Arch. Pharmacol. 272, 441 (l972); Bartholini, Pletscher, ibid. 274, 404 (1972). Metabolic pathways: Bartholini et al., J. Pharmacol. Exp. Ther. 183, 65 (1972). Parkinsonism treatment studies: Calne et al., Clin. Pharmacol. Ther. 14, 386 (1973).