title: [(3)H]-F13640, a novel, selective and high-efficacy serotonin 5-HT(1A) receptor agonist radioligand.
abstract: F13640 is a selective and high-efficacy serotonin 5-HT(1A) receptor agonist that demonstrates outstanding analgesic potential in different animal models. Here, we use the radiolabelled compound to further characterise its binding properties at 5-HT(1A) receptors. F13640 was tritium-labelled to 47 and 64 Ci/mmol specific activity and used as radioligand at membrane preparations of CHO cells expressing human (h) 5-HT(1A) receptors. The K (d) of [(3)H]-F13640 was 1.8 nM at h5-HT(1A) receptors as determined from saturation binding experiments. In association time-course experiments, k (obs) of [(3)H]-F13640 was 0.06 min(-1). Dissociation experiments performed in the presence of unlabelled F13640 as competing ligand yielded a k (off) value of 0.05 min(-1), resulting in a calculated K (d) of 1.4 nM. In comparison, [(3)H]-8-OH-DPAT had a k (obs) of 0.50 min(-1), a k (off) of 0.25 min(-1) and a calculated K (d) of 0.37 nM. Surprisingly, [(3)H]-F13640 dissociation kinetics were distinctly slower in the presence of WAY-100635 and spiperone as competing ligands when compared with the agonist competitors, F13640 and (+)8-OH-DPAT. The competitive binding profile of [(3)H]-F13640 with eight chemically diverse 5-HT(1A) receptor agonists and antagonists correlated highly (r = 0.996) with that of [(3)H]-8-OH-DPAT. In conclusion, [(3)H]-F13640 is a potent agonist radioligand at 5-HT(1A) receptors and may be a useful tool in pharmacological studies at native and recombinant 5-HT(1A) receptors. In addition, [(3)H]-F13640 dissociates more slowly from h5-HT(1A) receptors than [(3)H]-8-OH-DPAT, a kinetic property that might be related to its powerful analgesic effects as observed in vivo.
authors.affiliation: Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres Cedex, France. peter.heusler@pierre-fabre.com
authors.forename: Peter
authors.initials: P
authors.lastname: Heusler
authors.forename: Christiane
authors.initials: C
authors.lastname: Palmier
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Tardif
authors.forename: Sophie
authors.initials: S
authors.lastname: Bernois
authors.forename: Francis C
authors.initials: FC
authors.lastname: Colpaert
authors.forename: Didier
authors.initials: D
authors.lastname: Cussac
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D010880:Piperidines / Q000494:pharmacology*; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology*; D011869:Radioligand Assay; D044282:Receptor, Serotonin, 5-HT1A / Q000096:biosynthesis / Q000378:metabolism*; D058825:Serotonin 5-HT1 Receptor Agonists / Q000494:pharmacology*; D014316:Tritium
chemical_list: D010880:Piperidines; D011725:Pyridines; D044282:Receptor, Serotonin, 5-HT1A; D058825:Serotonin 5-HT1 Receptor Agonists; D014316:Tritium; C473959:befiradol
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