RT Journal Article
SR Electronic
T1 The PET Radioligand [<em>carbonyl</em>-<sup>11</sup>C]Desmethyl-WAY-100635 Binds to 5-HT<sub>1A</sub> Receptors and Provides a Higher Radioactive Signal Than [<em>carbonyl</em>-<sup>11</sup>C]WAY-100635 in the Human Brain
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 292
OP 303
VO 43
IS 3
A1 Andrée, Bengt
A1 Halldin, Christer
A1 Pike, Victor W.
A1 Gunn, Roger N.
A1 Olsson, Hans
A1 Farde, Lars
YR 2002
UL http://jnm.snmjournals.org/content/43/3/292.abstract
AB 5-Hydroxytryptamine (serotonin)-1A (5-HT1A) receptors are of key interest in research on the pathophysiology and treatment of psychiatric disorders. The PET radioligand [carbonyl-11C]WAY-100635 (11C-WAY), where WAY-100635 is 3H-(N-(2-(1-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridyl) cyclohexane-carboxamide, is commonly used for quantitation of 5-HT1A receptors in the human brain. The aim of this PET study was to compare 11C-WAY with the putative metabolite and selective radioligand [carbonyl-11C]desmethyl-WAY-100635 (11C-DWAY). Methods: A PET examination was performed on each of 5 healthy male volunteers after intravenous injection of 11C-WAY and 11C-DWAY on separate occasions. Radioactive metabolites in plasma were determined with high-performance liquid chromatography. The plasma metabolite–corrected input function was used in a kinetic compartment analysis. The simplified reference tissue model and peak equilibrium method, using the cerebellum as reference region, was applied for comparison of data. Results: For both radioligands, the highest radioactivity was observed in the neocortex and the raphe nuclei, whereas radioactivity was low in the cerebellum. The regional binding potentials were similar for the 2 radioligands. The brain uptake was more than 2-fold higher for 11C-DWAY than for 11C-WAY, in part because of higher delivery (first-order rate constant K1, 0.38 vs. 0.16). The time–activity curves were well described by a 3-compartment model for all regions, whereas uptake in the cerebellum could not be described by a 2-compartment model, supporting the existence of kinetically distinguishable nonspecific binding in the cerebellum or radioactive metabolites in the brain for both radioligands. Both radioligands were rapidly metabolized, and &lt;10% of the radioactivity in plasma represented unchanged 11C-WAY or 11C-DWAY at 10 min after injection. The metabolic pattern was similar for both radioligands, with the formation of radiolabeled cyclohexanecarboxylic acid and more polar components. For 11C-WAY, small amounts of an additional labeled metabolite comigrated with reference desmethyl-WAY-100635. Conclusion: The advantages of 11C-DWAY over 11C-WAY for research on central 5-HT1A receptors is supported by a significantly higher radioactivity signal at equipotent doses, providing improved imaging statistics and advantages in biomathematic modeling and the preclusion of 11C-DWAY as a metabolite interfering with PET measurements.