Regional distribution of parkinsonism-preventing endogenous tetrahydroisoquinoline derivatives and an endogenous parkinsonism-preventing substance-synthesizing enzyme in monkey brain

1,2,3,4-Tetrahydroisoquinoline (TIQ) and 1-benzyl-1,2,3,4-tetrahydroisoquin oline (1BnTIQ), which exist in the brain of several mammalian species, are parkinsonism-inducing substances, and 1-methyl-1,2,3,4-tetrahydroisoquinoli ne (1MeTIQ), which is enzymatically synthesized in rat brain, is a parkinso nism-preventing substance. in this study, we examined the regional distribu tion of contents of TIQ, 1MeTIQ, and 1BnTIQ, and activity of 1MeTIQ-synthes izing enzyme in monkey brain. The TIQ and 1BnTIQ contents in cerebrum and s ubstantia nigra, and the 1MeTIQ contents in striatum and substantia nigra w ere higher than those in other brain regions, and 1MeTIQ-synthetic activity was high in cerebrum and thalamus. We speculate that 1MeTIQ-synthesizing e nzyme may play an important role in idiopathic Parkinson's disease. (C) 199 9 Elsevier Science Ireland Ltd. All rights reserved.