• Dopamine;
  • 6–[18F]Fluoro-1-3,4-dihy-droxyphenylalanine;
  • Parkinson's disease;
  • Positron emission tomography)

Abstract: The tracers 6-[18F]fluoro-1-3,4-dihydroxyphenyl-alanine (6–[18F]fluoro-l-DOPA) and 1-[14C]DOPA were injected simultaneously into rhesus monkeys, and the time course of their metabolites was measured in the striatum and in the occipital and frontal cortices. In the striatum, 6-[18F]fluoro-L-DOPA was metabolized to 6–[18F]fluorodo-pamine, 3,4-dihydroxy-6–[18F]fluorophenylaceticacid, and 6–[18F]fluorohomovanillic acid. The metabolite pattern was qualitatively similar to that of 1-[14C]DOPA. 6–[18F]Fluorodopamine was synthesized faster than [14C]do-pamine. In the frontal cortex, the major metabolite was also 6–[18F]fluorodopamine or [14C]dopamine. In the occipital cortex, the major metabolite was 3-O-methyl-6–[18F]fluoro-L-DOPA. On the basis of these data, the images obtained with 6–[l8F]fluoro-l-DOPA and positron emission tomography in humans can now be interpreted in neurochemical terms.