Involvement of septal and striatal dopamine D-2 receptors in yawning behavior in rats.
A behavioral study was performed in an attempt to understand the neuronal mechanisms involved in yawning behavior in rats. Subcutaneous injections of low doses of apomorphine (0.05-0.25 mg/kg) or piribedil (0.2-1.0 mg/kg), which preferentially activate presynaptic dopamine autoreceptors at those doses, evoked yawning. Marked yawning responses were also elicited by both 3-PPP (5-20 mg/kg, SC) and TL-99 (1-2 mg/kg, SC). SK & F 38393, a dopamine D-1 receptor agonist, at doses ranging from 0.1 to 8.0 mg/kg (SC) induced neither yawning nor stereotypy. However, bromocriptine (0.5-32.0 mg/kg, SC), a dopamine D-2 receptor agonist, induced yawning for which the dose-response curves showed a bell-shaped form. After a higher dose of 32 mg/kg (SC) bromocriptine, some rats occasionally showed sniffing and sawdust chewing. Yawning responses induced by systemic injection of apomorphine, piribedil, 3-PPP or bromocriptine were wholly suppressed after treatment with sulpiride (10 mg/kg SC), a dopamine D-2 receptor antagonist. Bilateral injections of apomorphine (20 micrograms/side X 2), piribedil (100 micrograms/side X 2) or 3-PPP (50, 100 micrograms/side X 2) into the striatum or septum also elicited marked yawning. The results indicate that low doses of apomorphine, piribedil, 3-PPP, TL-99 or bromocriptine elicit yawning by stimulating dopamine D-2 receptors and striatal and septal dopaminergic systems may be related to the occurrence of yawning behavior.
D000818:Animals; D001921:Brain / Q000502:physiology*; D003342:Corpus Striatum / Q000502:physiology*; D007267:Injections; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017448:Receptors, Dopamine D2; D015000:Yawning / Q000187:drug effects*
D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2