CORRELATION OF STRIATAL FLUORODOPA UPTAKE IN THE MPTP MONKEY WITH DOPAMINERGIC INDEXES

Striatal F-18-6-fluorodopa (FD) uptake constants were measured by posi tron emission tomography in (1) normal cynomolgus monkeys and (2) a se ries of cynomolgus and rhesus monkeys that had received intracarotid i nfusions of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). After the animals were killed, the number and average size of dopaminergic neurons in the substantia nigra pars compacta were measured. Striatal levels of dopamine and its metabolites, and the striatal activities of the dopaminergic synthetic enzymes, were also determined. The striata l FD uptake constants showed highly significant positive corrrelations with both number and size of dopaminergic neurons, indicating atrophy of surviving neurons in MPTP-treated animals. The uptake constants al so showed significant positive correlations with striatal levels of do pamine, total catecholamines, and the activities of the synthetic enzy mes. Both histochemical and biochemical data on tyrosine hydroxylase s uggested some contralateral enzyme loss in these MPTP-treated monkeys, as well as decreased enzyme activity in surviving neurons on the lesi oned side. However, residual enzyme activities were apparently not rat e limiting to striatal FD uptake. It is concluded that PET-FD measurem ents by positron emission tomography provide a good index of the integ rity of the nigrostriatal pathway.