Presence of tetrahydroisoquinoline and 1-methyl-tetrahydro-isoquinoline in foods: compounds related to Parkinson's disease.

This is the first report confirming the presence of 1,2,3,4-tetrahydroisoquinoline (TIQ) and 1-methyl-1,2,3,4-tetrahydroisoquinoline(1MeTIQ) in a number of foods with a high 2-phenylethylamine content. These compounds were determined by gas chromatography-mass spectrometry. This study also confirmed that 1MeTIQ and TIQ can cross the blood-brain barrier in rat. Thus, these compounds, suspected to have relation to parkinson's disease, may accumulate in the brain from food sources.

Metabolism and brain accumulation of tetrahydroisoquinoline (TIQ) a possible parkinsonism inducing substance, in an animal model of a poor debrisoquine metabolizer.

4-Hydroxytetrahydroisoquinoline (4OH-TIQ) was detected as a metabolite of a possible parkinsonism-inducing substance, tetrahydroisoquinoline (TIQ), in rat liver microsomes and rat urine. Urinary excretion of 4OH-TIQ was significantly reduced in female DA rat, an animal model of a poor debrisoquine metabolizer. The female DA rat also showed significantly higher brain accumulation of TIQ. These results suggest that the metabolic detoxication process is depressed and TIQ accumulation in the brain is enhanced in a poor debrisoquine metabolizer, which may be one possible explanation for poor debrisoquine metabolizers being susceptible to Parkinson's disease.

A novel and neurotoxic tetrahydroisoquinoline derivative in vivo: formation of 1,3-dimethyl-1,2,3,4-tetrahydroisoquinoline, a condensation product of amphetamines, in brains of rats under chronic ethanol treatment.

Repeated amphetamine administration to rats under chronic ethanol intoxication resulted in the formation of 1,3-dimethyl-1,2,3,4-tetrahydroisoquinoline (1,3-DiMeTIQ), a novel metabolite of amphetamines. 1,3-DiMeTIQ was quantified with a sensitive, specific assay using gas chromatography-mass spectrometry. It was not found in the brains of rats given repeated amphetamine administration but no ethanol. The chronic ethanol-intoxicated rats subjected to repeated amphetamine administration exhibited behavioral abnormalities, such as repeated convulsions and curving of the back. 1,3-DiMeTIQ contents were markedly higher in the brain or plasma of rats manifesting abnormal behavior in comparison with those in rats behaving normally. Thus, the 1,3-DiMeTIQ content in the rat brain seems to have some relationship with behavioral abnormalities. This study also confirmed that 1,3-DiMeTIQ can cross the blood-brain barrier in the rat. Intraperitoneal 1,3-DiMeTIQ injections to rats caused behavioral symptoms similar to those observed in rats with chronic ethanol intoxication and repeated amphetamine administration. The effect of toxic doses of 1,3-DiMeTIQ on dopaminergic and serotonergic metabolism in the whole rat brain was also investigated.