title: Dopamine receptor agonist activity of some 5-(2-aminoethyl)carbostyril derivatives.
abstract: The potency of beta-adrenoreceptor agonists, e.g., isoproterenol, is strikingly increased by substitution of the meta catecholic hydroxyl group with the NH group of a carbostyril system. To explore the possibility that comparable potency enhancement might occur upon similar modification of the catechol ring of dopamine, a series of 5-(2-aminoethyl)carbostyril derivatives was prepared and examined for D-1 and D-2 dopamine receptor-stimulating activity. Only the parent compound, 5-(2-aminoethyl)-8-hydroxycarbostyril (2), produced measurable activation of dopamine-sensitive adenylate cyclase (29% at a concentration of 10 microM). Some of the compounds, however, did produce significant activity in tests, namely displacement of [3H]spiroperidol binding from bovine pituitary homogenate and an isolated perfused rabbit ear artery preparation, that measure interaction with D-2 receptors. Potency of the carbostyrils was enhanced by 8-hydroxylation and by appropriate substitution of the amino group of the ethylamine side chain. The most potent member of the series was 8-hydroxy-5-[2-[[2-(4-hydroxyphenyl)ethyl]-n-propylamino]ethyl] carbostyril (16b). This compound was about 3 times more effective than dopamine in the D-2 receptor tests. Clearly, the results of this study indicate that potency of dopamine receptor agonists is not increased by carbostyril replacement of the m-hydroxyl as is noted with the beta-adrenergic receptor agonists.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001158:Arteries / Q000502:physiology; D001667:Binding, Competitive; D002417:Cattle; D002421:Caudate Nucleus / Q000201:enzymology; D055598:Chemical Phenomena; D002621:Chemistry; D004298:Dopamine / Q000494:pharmacology; D004423:Ear / Q000098:blood supply; D006912:Hydroxyquinolines / Q000138:chemical synthesis / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D013134:Spiperone / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D006912:Hydroxyquinolines; D011954:Receptors, Dopamine; D013134:Spiperone; D000262:Adenylyl Cyclases; D004298:Dopamine