Involvement of central beta-adrenoceptors in the regulation of yawning responses.

A behavioral study was performed in an attempt to understand the role of central beta-adrenoceptors in yawning in rats. Yawning was evoked by apomorphine and piribedil, mixed dopamine D1/D2-receptor agonists, but not by SK&F 38393 [1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol], a dopamine D1-receptor agonist. The apomorphine-induced yawning was increased by pindolol, propranolol, indenolol, alprenolol and bukumolol which block the central beta-adrenoceptors, but not by the peripheral beta-adrenoceptor antagonists, carteolol and atenolol. These beta-adrenoceptor antagonists given alone did not elicit yawning. Conversely, the yawning was inhibited by salbutamol, a beta-adrenoceptor agonist, without being affected by prazosin, an alpha-adrenoceptor antagonist. The combined administration of SK&F 38393 and the beta-adrenoceptor antagonists did not induce yawning. The yawning elicited by either apomorphine or piribedil in combination with pindolol was suppressed by spiperone and YM-09151-2 [cis-N-(1-benzyl-2-methyl-pyrrolidin-3-yl)-5- chloro-2-methoxy-4-methylamino-benzamide], dopamine D2-receptor antagonists, and scopolamine, a muscarinic receptor antagonist, but not by SCH 23390 [R(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3- benzazepine-7-ol], a dopamine D1-receptor antagonist. Physostigmine or pilocarpine induced yawning, which was also enhanced by pindolol and propranolol. This enhanced yawning was inhibited by scopolamine, but not by spiperone, YM-09151-2 and SCH 23390.(ABSTRACT TRUNCATED AT 250 WORDS)