title: Effects of the putative D-1 antagonist SCH 23390 on stereotyped behaviour induced by the D-2 agonist RU24213.
abstract: The effects of the putative selective dopamine D-1 antagonist benzazepine SCH 23390 and of the selective dopamine D-2 antagonist Ro22-2586 on stereotypy induced by the selective D-2 agonist RU24213 were compared. RU24213 (0.5-15 mg/kg) dose-dependently induced stereo-typed behaviour characterised by continuous downward sniffing and locomotion. These responses were antagonised, as expected, by 40-200 micrograms/kg Ro22-2586, but surprisingly blocked by 40-200 micrograms/kg SCH 23390. The selectivities of these compounds for dopamine receptor subtypes were verified in terms of their relative abilities to displace the in vitro binding of 3H-piflutixol to striatal D-1 receptors and of 3H-spiperone to D-2 receptors. As SCH 23390 fails to influence D-2 mediated prolactin secretion or emesis in vivo, there appears to be no significant formation of an active metabolite of SCH 23390 with D-2 antagonist activity. Because SCH 23390 has some affinity for 5-hydroxytryptamine receptors, any effect on the serotonergic behavioural syndrome induced by 10 mg/kg 5-methoxy-N,N-dimethyltryptamine was also studied. The serotonergic responses of hind limb abduction, reciprocal forepaw treading and Straub tail were unaltered after 40-200 micrograms/kg SCH 23390, indicating no significant 5-HT blockade or non-specific depressant action at these doses which might influence the expression of stereotypy. Thus, these data are consistent with blockade of tonic D-1 dopaminergic activity that may influence the expression of behaviours initiated by D-2 dopaminergic stimulation.
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism; D004347:Drug Interactions; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology*; D008297:Male; D010627:Phenethylamines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects* / Q000378:metabolism; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D013239:Stereotyped Behavior / Q000187:drug effects*
chemical_list: D001552:Benzazepines; D007546:Isoquinolines; D010627:Phenethylamines; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C016868:N-n-propyl-N-phenylethyl-4(3-hydroxyphenyl)ethylamine hydrochloride; C032412:Ro 22-1319