title: Dopamine D1 receptors with enhanced agonist affinity and reduced antagonist affinity revealed by chemical modification.
abstract: In order to investigate the possibility that there may be two conformationally distinct dopamine D1 binding sites, the effect of lysine-modifying agents on striatal dopamine D1 receptors was investigated. Treatment with the distilbene derivative, 4,4'-diisothiocyanostilbene-2,2'-disulfonate, (DIDS), resulted in an irreversible D1 receptor inactivation that was associated with a 70% loss of binding sites. The remaining DIDS-insensitive sites displayed both a decreased affinity (approximately 5 fold) for the D1 antagonist SCH-23390 and an enhanced affinity of dopaminergic agonists (approximately 10 fold) for the agonist high-affinity form of the receptor. Pretreatment with Gpp(NH)p, a non-hydrolysable guanine nucleotide, prevented the formation of the agonist high-affinity form, indicating that these sites are G-protein-linked. Prior occupancy of D1 receptors with dopaminergic agonists and antagonists afforded no protection against DIDS inactivation, suggesting that a site outside the ligand binding subunit of the D1 receptor was modified. Taken together, these data suggest that [3H]SCH-23390 labels two conformationally distinct populations of dopamine D1 receptors.
authors.affiliation: Department of Pharmacology, University of Toronto, Ontario, Canada.
authors.forename: N H
authors.initials: NH
authors.lastname: Bzowej
authors.forename: H B
authors.initials: HB
authors.lastname: Niznik
authors.forename: P
authors.initials: P
authors.lastname: Seeman
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D011954:Receptors, Dopamine / Q000187:drug effects* / Q000378:metabolism; D017447:Receptors, Dopamine D1; D013267:Stilbenes / Q000494:pharmacology*
chemical_list: D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D013267:Stilbenes; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C022306:4,4'-dinitro-2,2'-stilbenedisulfonic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid