Validation of midbrain positron emission tomography measures for nigrostriatal neurons in macaques

Christopher A. Brown, Morvarid K. Karimi, Linlin Tian, Hugh Flores, Yi Su, Samer D. Tabbal, Susan K. Loftin, Stephen M. Moerlein, Joel S. Perlmutter

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


Objective: Development of an effective therapy to slow the inexorable progression of Parkinson disease requires a reliable, objective measurement of disease severity. In the present study, we compare presynaptic positron emission tomography (PET) tracer uptake in the substantia nigra (SN) to cell loss and motor impairment in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated nonhuman primates. Methods: Presynaptic PET tracers 6-[18F]- fluorodopa (FD), [11C]-2β-methoxy-3β-4-fluorophenyltropane (CFT), and [11C]-dihydrotetrabenazine (DTBZ) were used to measure specific uptake in the SN and striatum before and after a variable dose of MPTP in nonhuman primates. These in vivo PET-based measures were compared with motor impairment, as well as postmortem tyrosine hydroxylase-positive cell counts and striatal dopamine concentration. Results: We found the specific uptake of both CFT and DTBZ in the SN had a strong, significant correlation with dopaminergic cell counts in the SN (R2 = 0.77, 0.53, respectively, p < 0.001), but uptake of FD did not. Additionally, both CFT and DTBZ specific uptake in the SN had a linear relationship with motor impairment (rs = -0.77, -0.71, respectively, p < 0.001), but FD uptake did not. Interpretation: Our findings demonstrate that PET-measured binding potentials for CFT and DTBZ for a midbrain volume of interest targeted at the SN provide faithful correlates of nigral neuronal counts across a full range of lesion severity. Because these measures correlate with both nigral cell counts and parkinsonian ratings, we suggest that these SN PET measures are relevant biomarkers of nigrostriatal function.

Original languageEnglish
Pages (from-to)602-610
Number of pages9
JournalAnnals of neurology
Issue number4
StatePublished - Oct 2013


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