title: Functional differentiation of multiple dopamine D1-like receptors by NNC 01-0012.
abstract: Although members of the multiple vertebrate/mammalian dopamine D1 receptor gene family can be selectively classified on the basis of their molecular/phylogenetic, structural, and tissue distribution profiles, no subtype-specific discriminating agents have yet been identified that can functionally differentiate these receptors. To define distinct pharmacological/functional attributes of multiple D1-like receptors, we analyzed the ligand binding profiles, affinity, and functional activity of 12 novel NNC compounds at mammalian/vertebrate D1/D1A and D5/D1B, as well as vertebrate D1C/D1D, dopamine receptors transiently expressed in COS-7 cells. Of all the compounds tested, only NNC 01-0012 displayed preferential selectivity for vertebrate D1C receptors, inhibiting [3H]SCH-23390 binding with an estimated affinity (approximately 0.6 nM) 20-fold higher than either mammalian/vertebrate D1/D1A or D5/D1B receptors or the D1D receptor. Functionally, NNC 01-0012 is a potent antagonist at D1C receptors, inhibiting to basal levels dopamine (10 microM)-stimulated adenylyl cyclase activity. In contrast, NNC 01-0012 (10 microM) exhibits weak antagonist activity at D1A receptors, inhibiting only 60% of maximal cyclic AMP production by dopamine, while acting as a partial agonist at vertebrate D1B and D1D receptors, stimulating adenylyl cyclase activity by approximately 33% relative to the full agonist dopamine (10 microM), an effect that was blocked by the selective D1 receptor antagonist NNC 22-0010. These data clearly suggest that the benzazepine NNC 01-0012, despite lacking the N-methyl residue in the R3 position, is a selective and potent D1C receptor antagonist. Moreover, the differential signal transduction properties exhibited by NNC 01-0012 at these receptor subtypes provide further evidence, at least in vertebrates, for the classification of the D1C receptor as a distinct D1 receptor subtype.
authors.affiliation: Department of Pharmacology, University of Toronto, Ontario, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Sugamori
authors.forename: S A
authors.initials: SA
authors.lastname: Hamadanizadeh
authors.forename: M A
authors.initials: MA
authors.lastname: Scheideler
authors.forename: R
authors.initials: R
authors.lastname: Hohlweg
authors.forename: P
authors.initials: P
authors.lastname: Vernier
authors.forename: H B
authors.initials: HB
authors.lastname: Niznik
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D019556:COS Cells; D002645:Chickens; D018491:Dopamine Agonists / Q000378:metabolism / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D050641:Receptors, Dopamine D5; D013329:Structure-Activity Relationship; D014981:Xenopus
chemical_list: D001552:Benzazepines; C493605:DRD5 protein, human; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; C114704:NNC 01-0012; D017447:Receptors, Dopamine D1; D050641:Receptors, Dopamine D5