title: Effects of apomorphine, TL-99 and 3-PPP on yawning in rats.
abstract: Dopaminergic agonists, apomorphine (APO) (0.025-0.25 mg/kg, s.c.), TL-99 (0.5-3 mg/kg, s.c.) and 3-PPP (0.15-10 mg/kg, s.c.) elicited yawning in rats and the dose-response curves of all 3 compounds showed a bell-shaped form. Haloperidol (0.02 mg/kg, s.c.) reduced the yawning induced by DA-agonists to about 50%. The potencies of the DA-agonists in inducing yawning were APO greater than TL-99 greater than 3-PPP (comparable to potencies obtained in other in vivo tests, determining DA-ergic activity). The findings support the validity of the yawning phenomenon as a screening test for DA-agonists. Additionally, it was found that apomorphine induced yawning was significantly and dose-dependently enhanced by the beta-agonist, formoterol. This effect was counteracted by scopolamine, not changed by metergoline and further increased by l-propranolol. These data support the hypothesis of cholinergic involvement in yawning and indicate a role, though unclear at present, of beta-receptors in this behaviour.
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D051381:Rats; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D009281:Naphthalenes; D010880:Piperidines; D013764:Tetrahydronaphthalenes; C016893:2-(N,N-dimethylamino)-6,7-dihydroxytetralin; C026539:preclamol; D006220:Haloperidol; D001058:Apomorphine