Stanton J A, Beer M S
Merck, Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, UK.
Eur J Pharmacol. 1997 Feb 12;320(2-3):267-75. doi: 10.1016/s0014-2999(96)00914-4.
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.
化合物的效价和效能取决于受体储备，因此在分析系统中估算该参数能够更有意义地解释所产生的数据。本研究描述了一种方法，通过该方法，使用激动剂诱导的[35S]鸟苷5'-[γ-硫代]三磷酸（[35S]GTPγS）结合试验，测定表达人5-羟色胺1A受体的HeLa细胞系相对于5-羟色胺（5-HT）的受体储备程度，随后比较几种化合物的效价和相对效能。在用苄非他明进行不可逆拮抗后，5-HT产生的pKA为7.3，而饱和分析得出的pKobs为8.4，表明存在高亲和力和低亲和力状态的受体。20%的受体占有率引发了与受体储备存在相一致的半数最大功能反应。5-HT、5-羧酰胺色胺（5-CT）、8-羟基-二丙基氨基-四氢萘（8-OH-DPAT）、5-甲氧基-3-（1,2,3,6-四氢吡啶-4-基）-1H-吲哚（RU24969）、丁螺环酮、吉哌隆、美舒麦角和舒马曲坦具有同等效力。1-（2-甲氧基苯基）-4-[4-（2-邻苯二甲酰亚胺基）丁基]哌嗪（NAN 190）显示出相对效能降低和甲硫哒嗪反向激动作用。
