title: Selective blockade of dopamine D-1 receptor by SCH 23390 affects dopamine agonist binding to 3H-spiperone labeled D-2 receptors in rat striatum.
abstract: This study investigated the effects of selective blockade of dopamine D-1 receptors by SCH 23390 and selective stimulation of the receptors by SKF 38393 on the binding characteristics of 3H-spiperone labeled D-2 receptors in rat striatum. Selective blockade of D-1 receptors by 50 nM SCH 23390 significantly decreased the affinity of dopamine agonist for 3H-spiperone labeled D-2 receptors, but did not influence dopamine antagonist binding to D-2 receptors. Selective stimulation of D-1 receptors by SKF 38393 (100 nM) did not affect either dopamine agonist or antagonist binding to D-2 receptors. The characteristics of the effect of SCH 23390 on dopamine agonist binding to D-2 receptors was similar to those of GTP, but different from those of sodium ion. This effect could not be due to a direct modification of D-2 receptors by SCH 23390. Pertussis toxin (IAP) treatment significantly decreased the affinity of dopamine agonist for D-2 receptors and reduced the abilities of both SCH 23390 and GTP to decrease the affinity of dopamine agonist for D-2 receptors. These results suggest, therefore, putative interregulatory mechanism between dopamine D-1 and D-2 receptors and the possible involvement of a pertussis toxin sensitive protein in this mechanism.
authors.affiliation: Department of Pharmacology, Hiroshima University School of Medicine, Japan.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Segawa
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D001667:Binding, Competitive / Q000187:drug effects; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D015259:Dopamine Agents / Q000494:pharmacology*; D004873:Ergolines / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D037342:Pertussis Toxin; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D012964:Sodium / Q000494:pharmacology; D013134:Spiperone; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D015259:Dopamine Agents; D004873:Ergolines; D011954:Receptors, Dopamine; D010566:Virulence Factors, Bordetella; D019257:Quinpirole; D013134:Spiperone; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D006160:Guanosine Triphosphate; D012964:Sodium; D037342:Pertussis Toxin; D004298:Dopamine