Pargyline‐Sensitive selective accumulation of a radiolabeled MPTP analog in the primate cerebral cortex and basal ganglia

The distribution of radioiodinated N‐methyl‐4‐(4‐hyroxy‐3‐iodobenzyl)‐1,2,3,6‐tetrahydropyridine (MHTP), an analog of the reportedly nontoxic N‐methyl‐4‐benzyl‐1,2,3,6‐tetrahydropyridine, (4‐homo‐MPTP), has been studied in the primate. [¹²³I]‐MHTP‐derived radioactivity exhibited a progressive accumulation and prolonged retention within the primateeye. Following injection, [¹²³I]MHTP rapidly accumulated within the primate brain and was subssequently oxidized to a radiolabeled metabolite. The half‐life of [¹²³I]MHTP‐derived radioactivity within the primate brain was 50 min. The highest concentrations of radioactivity were found in the caudate‐putamen and the frontal, temproal and cingulate cortices; the substantia nigra and inferior olivary nucleus were labeled with medium intensity. Very low concentrations of radiolabel were detected in the cerebellum and white matter, Selective accumulation of [¹²⁵I]MHTP‐derived radioactivity within these structures was blocked by pretreatment with pargyline, suggesting that nonoamine oxidase B is involved in the bioactivation of radioiodinated MHTP.