caa a22 4500 469078391 CHVBK 20180323132942.0 cr unu---uuuuu 170328e19921001xx s 000 0 eng 10.1007/BF00171076 doi (NATIONALLICENCE)springer-10.1007/BF00171076 Differential coupling of 5-HT1A receptors occupied by 5-HT or 8-OH-DPAT to adenylyl cyclase [Elektronische Daten] [Annie Varrault, Joel Bockaert] Summary: Human serotonin (5-hydroxytryptamine, 5-HT)-1A receptors have been transfected in NIH-3T3 cells, and their coupling to adenylyl cyclase was analysed depending on (1) the number of receptor expressed, (2) the experimental conditions used, (3) the nature of the agonists. Two monoclonal cell lines were used, expressing low (45 fmol/mg) and high (500 fmol/mg) levels of 5-HT1A receptor. Two methods were tested to study the negative coupling of the transfected 5-HT1A receptors to adenylyl cyclase: (1) measurement of CAMP production in intact cells, (2) measurement of adenylyl cyclase activity in vitro on membrane preparations. Studies on intact cells revealed that an increase in the receptor concentration was followed by (1) an increase in the efficacies of 5-HT, 5-CT (5-carboxamidotryptamine) and 8-hydroxy2-(di-n-propylamino)tetralin (8-OH-DPAT), (2) a 2 to 3-fold increase in the potency of 5-CT and 8-OH-DPAT, but no change in the potency of 5-HT. In membrane preparations, 8-OH-DPAT dose-response curve was shifted leftwards when the receptor concentration became higher whereas the corresponding shift was smaller for 5-HT and absent for 5-CT. Surprisingly, on membrane preparations, 8-OH-DPAT was a partial agonist relative to 5-HT. The relative efficacy of 8-OH-DPAT was lower in the clone expressing the lowest level of receptor. This partial agonist behavior of 8-OH-DPAT could be modulated by the ionic conditions under which the adenylyl cyclase activity was measured. When physiological intracellular concentrations of Na+, Mg2+ and K+ were used, 8-OH-DPAT became an almost full agonist relative to 5-HT. These data indicate that (1) the classical pharmacological models do not exactly fit with characteristics of the negative coupling between transfected 5-HT1A receptors and adenylyl cyclase; (2) on membranes, the experimental procedures (ionic conditions) can modify this coupling differently depending on the nature of the agonist. Springer-Verlag, 1992 Serotonin-1A receptor nationallicence Adenylyl cyclase nationallicence 8-OH-DPAT nationallicence Partial agonism nationallicence 5-HT : 5-hydroxytryptamine (serotonin) nationallicence 8-OHDPAT : 8-hydroxy-2-(di-n-propylamino)-tetraline nationallicence 5-CT : 5-carboxamidotryptamine nationallicence IBMX : isobutyl methyl xanthine nationallicence BSA : bovine serum albumine nationallicence EC50 : half maximal efficacy nationallicence DXM : dexamethasone nationallicence PTX : Bordetella pertussis toxin nationallicence G protein : GTP-binding protein nationallicence Varrault Annie Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Rue de la Cardonille, F-34094, Montpellier Cedex 5, France aut Bockaert Joel Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Rue de la Cardonille, F-34094, Montpellier Cedex 5, France aut Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/4(1992-10-01), 367-374 0028-1298 346:4<367 1992 346 210 https://doi.org/10.1007/BF00171076 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00171076 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Varrault Annie Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Rue de la Cardonille, F-34094, Montpellier Cedex 5, France aut NATIONALLICENCE 700 1- Bockaert Joel Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Rue de la Cardonille, F-34094, Montpellier Cedex 5, France aut NATIONALLICENCE 773 0- Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/4(1992-10-01), 367-374 0028-1298 346:4<367 1992 346 210 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer