Stimulation of a D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland decreases the responsiveness of the beta-adrenoceptor: biochemical mechanism.
In experiments using a cell-free homogenate of the intermediate lobe of the hypophysis of the rat, apomorphine, a dopaminergic agonist, diminished both basal and L-isoproterenol-stimulated adenylate cyclase activity; dopaminergic antagonists from several chemical families reversed these inhibitory effects of apomorphine. Apomorphine diminished the ability of GTP to enhance both basal and L-isoproterenol-stimulated adenylate cyclase activity but did not directly interfere with the interaction between the beta-adrenoceptor and L-isoproterenol. The affinity of the D-2 dopamine receptor in the intermediate lobe for each dopaminergic antagonist used in this study was estimated from a mathematical analysis of the data. (Endocrinology 108: 420, 1981)
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D002474:Cell-Free System; D004305:Dose-Response Relationship, Drug; D005476:Fluphenazine / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D011954:Receptors, Dopamine / Q000378:metabolism*
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D011954:Receptors, Dopamine; D006160:Guanosine Triphosphate; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D001058:Apomorphine; D005476:Fluphenazine