Characterisation of a cloned human 5-HT1A receptor cell line using [35S]GTP gamma S binding.
Compound potencies and efficacies depend upon receptor reserve and hence estimating this parameter in assay systems allows for a more meaningful interpretation of the data generated. This study describes a method whereby the degree of receptor reserve, with respect to 5-hydroxytryptamine (5-HT), was determined for a HeLa cell line expressing the human 5-HT1A receptor using the agonist-induced [35S]guanosine 5'[gamma-thio]triphosphate ([35S]GTP gamma S) binding assay, followed by a comparison of the potencies and relative efficacies of several compounds. Following irreversible antagonism with benextramine 5-HT yielded a pKA of 7.3, compared with a pKobs of 8.4 from saturation analysis, indicating the presence of high and low affinity state receptors. A 20% receptor occupancy elicited a half-maximal functional response consistent with the presence of receptor reserve. 5-HT, 5-carboxamidotryptamine (5-CT), 8-hydoxy-dipropylamino-tetralin (8-OH-DPAT), 5-methoxy-3-(1,2,3,6-tetrahydropyridin-4-yl)-1 H-indole (RU24969), buspirone, gepirone, mesulergine and sumatriptan were equally efficacious. 1-(2-Methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine (NAN 190) displayed reduced relative efficacy and methiothepin inverse agonism.
Stanton
J A
JA
Merck, Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, UK.
Beer
M S
MS
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000378:metabolism / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D002999:Clone Cells; D003538:Cystamine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D011869:Radioligand Assay; D011985:Receptors, Serotonin / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D014316:Tritium
D000317:Adrenergic alpha-Antagonists; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D014316:Tritium; D012701:Serotonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C029998:benextramine; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D003538:Cystamine