title: Permissive role of D-1 receptor stimulation by endogenous dopamine for the expression of postsynaptic D-2-mediated behavioural responses. Yawning in rats.
abstract: Low doses of BHT 920, LY 171555 and (+)3PPP, three dopamine agonists selective for D-2 receptors, induced yawning in rats. This effect was reduced by the selective D-1 antagonist SCH 23390 but the antagonism did not exceed a 50% reduction from the control values. In contrast, the selective D-2 antagonist (-)sulpiride completely abolished agonist-induced yawning. A 6 h reserpine pretreatment (5 mg/kg i.p.), which depletes brain dopamine (DA) by about 95%, reduced agonist-induced yawning by an extent similar to SCH 23390; in the reserpinized rats, SCH 23390 completely lost the property of blocking agonist-induced yawning while (-)sulpiride retained it. Two 5HT receptor antagonist, ketanserin and metergoline failed to influence agonist-induced yawning. The reportedly selective D-1 agonist, SKF 38393, failed to induce yawning in normal rats as well as in rats pretreated with reserpine 6 or 16 h earlier. If one excludes that SCH 23390 and the D-2 agonists interact with the same DA-receptors, the data are consistent with the possibility that stimulation of D-1 receptors by endogenous DA plays a permissive-facilitatory role for the behavioural expression of D-2 receptor activation.
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D001923:Brain Chemistry / Q000187:drug effects; D004298:Dopamine / Q000502:physiology*; D004873:Ergolines / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008711:Metergoline / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D019257:Quinpirole; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D012110:Reserpine / Q000494:pharmacology; D013469:Sulpiride / Q000494:pharmacology; D015000:Yawning / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D001381:Azepines; D001552:Benzazepines; D004873:Ergolines; D010880:Piperidines; D011954:Receptors, Dopamine; D008711:Metergoline; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; C024763:talipexole; D013469:Sulpiride; D012110:Reserpine; D007650:Ketanserin; C026539:preclamol; D007608:Kainic Acid; D004298:Dopamine