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Fluorine-18-FPCT: a PET radiotracer for imaging dopamine transporters
M M Goodman1, R Keil, T M Shoup
1Emory Center for Positron Emission Tomography, Atlanta, Georgia, USA.
Unlabelled:
Fluorine-18-labeled 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)-8-[-3-fluoropropyl) nortropane (FPCT) has been synthesized as a new dopamine transporter imaging agent.
Methods:
Fluorine-18 was introduced into 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)-8-[-3-fluoropropyl) nortropane by preparation of 1-[18F]fluoro-3-iodopropane followed by alkylation of 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)nortropane.
Results:
Tissue distribution studies in rats with [18F]FPCT showed high striatal uptake (0.70% dose/g at 60 min; 0.38% dose/g at 120 min) and good striatal-to-cerebellum ratios (5.5 at 60 min; 6.2 at 120 min). Imaging studies in rhesus monkeys (n = 2) with [18F]FPCT showed high uptake and retention in the putamen (P) (P = 0.03%-0.12% dose/g; at 115 min) and good putamen-to-cerebellum ratios of 3.40-3.43 at 115 min. Plasma metabolites were analyzed in rhesus monkeys (n = 2) by ether extraction and HPLC. The radioactivity in the ether-extractable fraction displayed a single peak that corresponded on HPLC to unmetabolized authentic FPCT.
Conclusion:
These results suggest that [18F]FPCT is an excellent candidate for PET imaging of dopamine transporters.