Pauwels P J, Dupuis D S, Perez M, Halazy S
Centre de Recherche Pierre Fabre, Département de Biologie Cellulaire et Moléculaire, Castres, France.
Naunyn Schmiedebergs Arch Pharmacol. 1998 Oct;358(4):404-10. doi: 10.1007/pl00005271.
[35S]GTPgammaS binding responses can be used to measure differences between the intrinsic activity of ligands at human 5-hydroxytrypamine-(1A) (h 5-HT1A) receptors expressed in recombinant cell lines. The maximal [35S]GTPgammaS binding response to 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was lower than that to 5-HT in a recombinant C6-glial membrane preparation and dependent on the GDP concentration: it was attenuated by about 60% vs 5-HT by increasing the concentration of GDP from 0.3 to 30 and 300 microM. Whereas dimerization of 8-OH-DPAT almost did not affect its potency at h 5-HT1A receptors (pEC50: 7.45 and 7.40 for 8-OH-DPAT and its dimer at 30 microM GDP), it increased efficacy at h 5-HT1A receptors. The maximal response to the 8-OH-DPAT dimer was systematically greater than the response to 8-OH-DPAT and identical to that to 5-HT; moreover in contrast to the 8-OH-DPAT monomer, the maximal response to the dimer was unaffected by increasing the GDP concentration. An enhanced 135S]GTPgammaS binding response (44 to 63% vs 8-OH-DPAT) was also observed in the hippocampus, lateral septum, dorsal raphe and cingulate cortex of guinea-pig brain sections using autoradiography of 5-HT1A receptor-activated G-proteins. Hence, the 8-OH-DPAT dimer shows increased efficacy at 5-HT1A receptors compared to 8-OH-DPAT. The differential regulation of the maximal agonist responses by GDP suggests that the [35S]GTPgammaS binding responses to these two ligands could be mediated by different G-protein subtypes upon activation of the 5-HT1A receptor.
[35S]GTPγS结合反应可用于测量配体在重组细胞系中表达的人5-羟色胺-(1A)（h 5-HT1A）受体上的内在活性差异。在重组C6-胶质细胞膜制剂中，对8-羟基-2-(二正丙基氨基)四氢萘（8-OH-DPAT）的最大[35S]GTPγS结合反应低于对5-羟色胺（5-HT）的反应，且依赖于GDP浓度：当GDP浓度从0.3微摩尔增加到30微摩尔和300微摩尔时，与5-HT相比，其反应减弱约60%。虽然8-OH-DPAT二聚化几乎不影响其在h 5-HT1A受体上的效力（在30微摩尔GDP时，8-OH-DPAT及其二聚体的pEC50分别为7.45和7.40），但它增加了在h 5-HT1A受体上的效能。对8-OH-DPAT二聚体的最大反应系统性地大于对8-OH-DPAT的反应，且与对5-HT的反应相同；此外，与8-OH-DPAT单体不同，对二聚体的最大反应不受GDP浓度增加的影响。使用5-HT1A受体激活的G蛋白的放射自显影技术，在豚鼠脑切片的海马体、外侧隔区、中缝背核和扣带回皮质中也观察到[35S]GTPγS结合反应增强（相对于8-OH-DPAT增加44%至63%）。因此，与8-OH-DPAT相比，8-OH-DPAT二聚体在5-HT1A受体上显示出增加的效能。GDP对最大激动剂反应的差异调节表明，对这两种配体的[35S]GTPγS结合反应可能在5-HT1A受体激活后由不同的G蛋白亚型介导。
