Involvement of beta-adrenoceptors in regulation of the yawning induced by neuropeptides, oxytocin and alpha-melanocyte-stimulating hormone, in rats.
The present study was undertaken to investigate whether beta-adrenoceptors are involved in regulation of yawning responses to oxytocin and alpha-melanocyte-stimulating hormone (alpha-MSH) in rats. Oxytocin administered intracerebroventricularly (ICV) at doses of 50 and 100 ng/rat elicited yawning. alpha-MSH (20 micrograms/rat, ICV) elicited not only yawning but also stretching and body shaking. RS-86 (2-ethyl-8-methyl-2,8-diazaspiro-(4,5)-decan-1,3-dion hydrobromide), a putative muscarinic M1 receptor agonist, administered ICV at a lower dose of 100 micrograms/rat and subcutaneously (SC) at doses of 0.25-2.5 mg/kg also elicited yawning. The yawning responses produced by these agents were markedly increased by intraperitoneal (IP) pretreatment with a beta-adrenoceptor antagonist, pindolol (20 mg/kg), which per se did not elicit yawning. The yawning induced by oxytocin (50 ng/rat, ICV) plus pindolol, but not that by alpha-MSH (20 micrograms/rat, ICV) or RS-86 (0.5 mg/kg, SC) plus pindolol, was inhibited by [d(CH2)5,Tyr(Me)2,Orn8]-vasotocin (100 ng/rat, ICV), an oxytocin receptor antagonist. The yawning induced by oxytocin, alpha-MSH, or RS-86 administered in combination with pindolol was inhibited by scopolamine (0.5 mg/kg, SC), a mucarinic receptor antagonist, without being affected by spiperone (0.5 mg/kg, SC), a dopamine D2 receptor antagonist. The results suggest that the yawning produced by the neuropeptides oxytocin and alpha-MSH is modulated by beta-adrenoceptor activity in an inhibitory manner as that produced by muscarinic M1 receptor agonists, and that it involves cholinergic, but not dopaminergic, activation.
Fujikawa
M
M
Department of Pharmacology, School of Medicine, Fukuoka University, Japan.
Yamada
K
K
Nagashima
M
M
Furukawa
T
T
D000818:Animals; D007276:Injections, Intraventricular; D008297:Male; D018721:Muscarinic Agonists; D010121:Oxytocin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010869:Pindolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013388:Succinimides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015000:Yawning / Q000187:drug effects*; D000521:alpha-MSH / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D018721:Muscarinic Agonists; D011943:Receptors, Adrenergic, beta; D013388:Succinimides; C001886:2-ethyl-8-methyl-2,8-diazaspiro(4,5)decane-1,3-dione; D010121:Oxytocin; D000521:alpha-MSH; D010869:Pindolol