Dopamine D1 receptor coupling to Gs/olf and Gq in rat striatum and cortex: a scintillation proximity assay (SPA)/antibody-capture characterization of benzazepine agonists.
Cloned, human dopamine D(1) receptors recruit multiple effectors but the G-protein subtype(s) activated by cerebral populations remain poorly defined, a question addressed using a rapid immunocapture technique. In rat striatum, dopamine (DA) and four selective, benzazepine agonists at D(1) receptors concentration-dependently enhanced [(35)S]GTPgammaS binding to Galphas/olf. For all drugs, Galphaq was also recruited with similar potencies and efficacies. Comparable observations were made in the cortex wherein profiles of Galphas/olf vs Galphaq activation were also highly correlated. In contrast to Galphas/olf and Galphaq, Galphao and Galphai were activated neither in the striatum nor in the cortex, except for SKF82958. As compared to DA, both SKF81297 and SKF82958 were full agonists at Gs/olf and Gq in cortex and striatum, whereas SKF38393 behaved as a partial agonist. Likewise, the "atypical" agonist, SKF83959 only partially activated Galphaq and also Gs/olf in these two regions. In both striatum and cortex, the selective D(1) receptor antagonist, SCH23390, abolished the recruitment of Galphaq and Galphas by DA, and the action of DA was partially attenuated by SKF83959. These findings demonstrate that, in native CNS tissue, DA and other D(1) receptor agonists activate Galphas and Galphaq with similar potencies and efficacies, suggesting their recruitment via pharmacologically-indistinguishable populations of D(1) receptors, and show that SPA technology is well-adapted to study the coupling of native DA receptors.
Mannoury la Cour
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Institut de Recherche Servier, Psychopharmacology Department, 125, chemin de Ronde, 78290 Croissy sur Seine, France. clotilde.mannourylacour@fr.netgrs.com
Vidal
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Pasteau
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Cussac
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Millan
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D000818:Animals; D000906:Antibodies / Q000378:metabolism* / Q000494:pharmacology; D000918:Antibody Specificity; D001552:Benzazepines / Q000494:pharmacology; D001666:Binding Sites, Antibody; D001667:Binding, Competitive / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000276:immunology / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000276:immunology / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D011869:Radioligand Assay / Q000379:methods; D051381:Rats; D017447:Receptors, Dopamine D1 / Q000378:metabolism*
D000906:Antibodies; D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D017447:Receptors, Dopamine D1; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019205:GTP-Binding Protein alpha Subunits, Gs