title: Characterization of [3H]YM060, a potent and selective 5-HT3 receptor radioligand, in the cerebral cortex of rats.
abstract: The binding properties of a new radioligand, [methyl-3H]-(-)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl]-4,5,6,7- tetrahydro-1H-benzimidazole monohydrochloride ([3H]YM060), were studied in membranes of the rat cerebral cortex. [3H]YM060 rapidly associated with its binding sites in membranes and reversibly dissociated. Saturation analysis revealed that the specific binding of [3H]YM060 was saturable and non-specific binding was low. Scatchard analysis yielded a linear plot, suggesting a single population of binding sites with a dissociation constant (Kd) of 8.4 +/- 0.2 pM (n = 3) and the kinetic Kd determined from the association constant (K+1) and the dissociation rate constant (K-1) was similar. The maximum number of binding sites (Bmax) was 37.0 +/- 0.8 fmol/mg protein (n = 3). [3H]YM060 binding was potently and stereospecifically inhibited by serotonin (5-HT)3 receptor agonists and antagonists. Other 5-HT receptor ligands such as 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), methysergide and ketanserin were inactive to inhibit specific binding at 10(-4) M. These results suggest that [3H]YM060 is a highly potent and selective 5-HT3 receptor radioligand and will be useful in the further analysis of 5-HT3 receptors.
authors.affiliation: Department of Internal Medicine, University of Tsukuba, Ibaraki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Akuzawa
authors.forename: K
authors.initials: K
authors.lastname: Miyata
authors.forename: H
authors.initials: H
authors.lastname: Fukutomi
mesh_terms: D000818:Animals; D001562:Benzimidazoles / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology*; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism / Q000648:ultrastructure*; D007700:Kinetics; D008297:Male; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism*; D012680:Sensitivity and Specificity; D012702:Serotonin Antagonists / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology; D014316:Tritium
chemical_list: D001562:Benzimidazoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D014316:Tritium; C071315:ramosetron