UNLABELLED: (11)C-ABP688 (3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-(11)C-methyl-oxime), a noncompetitive and highly selective antagonist for the metabotropic glutamate receptor subtype 5 (mGluR5), was evaluated for its potential as a PET agent. METHODS: ABP688 was radiolabeled with (11)C by reacting (11)C-methyl iodide with the sodium salt of desmethyl-ABP688 (3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone oxime). The affinity of (11)C-ABP688 for mGluR5 was determined by Scatchard analysis using rat whole-brain membranes (without cerebellum). Ex vivo autoradiography, biodistribution, and PET studies with (11)C-ABP688 were performed on rats, wild-type mice, and mGluR5-knock-out mice. RESULTS: The overall synthesis time was 45-50 min from the end of radionuclide production. (11)C-ABP688 was obtained in good radiochemical yield (35% +/- 8%, n = 17, decay corrected), and the specific radioactivity was 150 +/- 50 GBq/mumol (n = 17) at the end of the synthesis. Scatchard analysis revealed a single high-affinity binding site with a dissociation constant of 1.7 +/- 0.2 nmol/L and a maximum number of binding sites of 231 +/- 18 fmol/mg of protein. Ex vivo autoradiography in wild-type mice and rats showed a heterogeneous distribution pattern consistent with the known distribution of mGluR5 in the brain, with the highest uptake in hippocampus, striatum, and cortex. Blocking studies by coinjection of (11)C-ABP688 and unlabeled 2-methyl-6-(3-methoxyphenyl)ethynyl-pyridine (1 mg/kg), an antagonist for mGluR5, revealed up to 80% specific binding in rat brain. In mGluR5-knock-out mouse brain, a homogeneous and markedly reduced accumulation of (11)C-ABP688 was observed. PET studies on rats and mice using a small-animal PET scanner also demonstrated radioactivity uptake in the brain regions known to be rich in mGluR5. In contrast, radioactivity uptake in mGluR5-knock-out mice was fairly uniform, substantiating the specificity of (11)C-ABP688 binding to mGluR5. CONCLUSION: (11)C-ABP688 is a selective tracer for imaging mGluR5 in vivo in rodents and may offer a future tool for imaging mGluR5 in humans using PET.
UNLABELLED: (11)C-ABP688 (3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-(11)C-methyl-oxime), a noncompetitive and highly selective antagonist for the metabotropic glutamate receptor subtype 5 (mGluR5), was evaluated for its potential as a PET agent. METHODS:ABP688 was radiolabeled with (11)C by reacting (11)C-methyl iodide with the sodium salt of desmethyl-ABP688 (3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone oxime). The affinity of (11)C-ABP688 for mGluR5 was determined by Scatchard analysis using rat whole-brain membranes (without cerebellum). Ex vivo autoradiography, biodistribution, and PET studies with (11)C-ABP688 were performed on rats, wild-type mice, and mGluR5-knock-out mice. RESULTS: The overall synthesis time was 45-50 min from the end of radionuclide production. (11)C-ABP688 was obtained in good radiochemical yield (35% +/- 8%, n = 17, decay corrected), and the specific radioactivity was 150 +/- 50 GBq/mumol (n = 17) at the end of the synthesis. Scatchard analysis revealed a single high-affinity binding site with a dissociation constant of 1.7 +/- 0.2 nmol/L and a maximum number of binding sites of 231 +/- 18 fmol/mg of protein. Ex vivo autoradiography in wild-type mice and rats showed a heterogeneous distribution pattern consistent with the known distribution of mGluR5 in the brain, with the highest uptake in hippocampus, striatum, and cortex. Blocking studies by coinjection of (11)C-ABP688 and unlabeled 2-methyl-6-(3-methoxyphenyl)ethynyl-pyridine (1 mg/kg), an antagonist for mGluR5, revealed up to 80% specific binding in rat brain. In mGluR5-knock-out mouse brain, a homogeneous and markedly reduced accumulation of (11)C-ABP688 was observed. PET studies on rats and mice using a small-animal PET scanner also demonstrated radioactivity uptake in the brain regions known to be rich in mGluR5. In contrast, radioactivity uptake in mGluR5-knock-out mice was fairly uniform, substantiating the specificity of (11)C-ABP688 binding to mGluR5. CONCLUSION: (11)C-ABP688 is a selective tracer for imaging mGluR5 in vivo in rodents and may offer a future tool for imaging mGluR5 in humans using PET.
Authors: Christine DeLorenzo; Matthew S Milak; Kathleen G Brennan; J S Dileep Kumar; J John Mann; Ramin V Parsey Journal: Eur J Nucl Med Mol Imaging Date: 2011-01-29 Impact factor: 9.236
Authors: Alexandra Deschwanden; Beata Karolewicz; Anteneh M Feyissa; Valerie Treyer; Simon M Ametamey; Anass Johayem; Cyrill Burger; Yves P Auberson; Judit Sovago; Craig A Stockmeier; Alfred Buck; Gregor Hasler Journal: Am J Psychiatry Date: 2011-04-15 Impact factor: 18.112
Authors: Samuel A Barnes; Douglas J Sheffler; Svetlana Semenova; Nicholas D P Cosford; Anton Bespalov Journal: Biol Psychiatry Date: 2018-03-09 Impact factor: 13.382
Authors: Funda Akkus; Simon M Ametamey; Valerie Treyer; Cyrill Burger; Anass Johayem; Daniel Umbricht; Baltazar Gomez Mancilla; Judit Sovago; Alfred Buck; Gregor Hasler Journal: Proc Natl Acad Sci U S A Date: 2012-12-17 Impact factor: 11.205
Authors: William B Mathews; Hiroto Kuwabara; Kirstie Stansfield; Heather Valentine; Mohab Alexander; Anil Kumar; John Hilton; Robert F Dannals; Dean F Wong; Fabrizio Gasparini Journal: Synapse Date: 2014-08-19 Impact factor: 2.562