Cerebral Metabolism of 6–[18F]Fluoro‐l‐3,4‐Dihydroxyphenylalanine in the Primate

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.