Migration of tetrahydroisoquinoline, a possible parkinsonian neurotoxin, into monkey brain from blood as proved by gas chromatography-mass spectrometry.

1,2,3,4-Tetrahydroisoquinoline (TIQ) was quantitated by use of gas chromatography-mass spectrometry in brains and livers of marmosets which showed parkinsonism after daily subcutaneous injection of TIQ. TIQ showed greatly increased levels in the brains and livers of the TIQ-treated marmosets, with no detectable metabolites of TIQ. TIQ was present as an endogenous amine in the brains and livers of saline-treated marmosets at very low concentrations. It thus seems that TIQ can pass easily through the blood-brain barrier but cannot be metabolized in the brain or the liver. It is possible that TIQ accumulated in the brain may produce parkinsonism.