title: Interaction of cholinergic and dopaminergic influences on yawning behavior.
abstract: The possible interaction between cholinergic and dopaminergic influences in the induction of yawning behavior in the rat is explored resorting to several experimental approaches: comparison of the ontogeny of yawning behavior induced by physostigmine (0.15 mg/kg) and apomorphine (0.05 mg/kg); simultaneous injection of both drugs; "crossed blocking" experiments, in which the action of the cholinomimetic agent is examined after injection of spiroperidol (0.05 mg/kg) and that of apomorphine after scopolamine (0.25 mg/kg). While physostigmine-elicited yawning is highest in early postnatal days and tends to decline from the 7th day onwards, reaching its lowest level around 3 wk, yawning induced by apomorphine begins around the 9th day and increases thereafter to a plateau that is reached in the third week. No synergism on yawning behavior is observed by simultaneous injection of optimal or suboptimal doses of physostigmine and apomorphine. Scopolamine blocks apomorphine-induced yawning; spiroperidol blocks apomorphine- but potentiates physostigmine-induced yawning, both in 15-day-old and young adult rats. Two 5-HT uptake blockers, citalopram (10-20 mg/kg) and fluoxetin (10-20 mg/kg) potentiate physostigmine - but not apomorphine-elicited yawning. On the basis of these results a tentative model of "in series" organization of dopaminergic and cholinergic influences on yawning behavior is proposed.
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D001572:Benzofurans / Q000494:pharmacology; D015283:Citalopram; D005473:Fluoxetine / Q000494:pharmacology; D008711:Metergoline / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D011437:Propylamines / Q000494:pharmacology; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000502:physiology*; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D012601:Scopolamine / Q000494:pharmacology; D013134:Spiperone / Q000494:pharmacology
chemical_list: D001572:Benzofurans; D011437:Propylamines; D011950:Receptors, Cholinergic; D011954:Receptors, Dopamine; D005473:Fluoxetine; D015283:Citalopram; D008711:Metergoline; D013134:Spiperone; D010830:Physostigmine; D012601:Scopolamine; D001058:Apomorphine