ABSTRACT
The present experiments were performed to investigate effects of a Kampo (Japanese herbal) medicine, Kambaku-taiso-to (Gan-mai-da-zao-tang), on incidence of yawning in rats. Physostigmine, a cholinesterase inhibitor, 0.05-0.1mg/kg s. c., induced yawning responses with a marked effect at 0.05mg/kg. Pilocarpine, a muscarinic receptor agonist, 1-2mg/kg s. c., also induced yawning responses, the maximum effect being observed at a dose of 2mg/kg. Talipexole, a dopaminergic D-2 receptor agonist, 0.02mg/kg s. c., also induced yawning. Kambaku-taiso-to, 250-1, 000mg/kg, was orally administered 30min before injection of physostigmine, pilocarpine or talipexole. The yawning induced by both cholinergic and dopaminergic agents was reduced in a dose-dependent manner by Kambaku-taiso-to. All the yawning responses to cholinergic and dopaminergic agents were also reduced by rauwolscine 0.5mg/kg, yohimbine 2.5mg/kg, α-2 adrenoceptor antagonists, and by scopolamine 0.5mg/kg—muscarinic receptor antagonist. The present findings thus suggest that Kambaku-taiso-to exerts a suppressive effect on the incidence of yawning, and dopaminergic and cholinergic suppression and the indirect suppressive mechanism mediated by the central adrenergic nerve are associated with this suppression.
ABSTRACT
The present experiments were performed to investigate the potential role of Kambaku taiso-to (Gan mai da zao tang) in modifying the occurrence of yawning in rats. Subcutaneous injection of talipexole, a selective dopamine D-2 receptor agonist, at 5-100μg/kg, elicits yawning behavior for over one hour, the maximal effect being observed at a dose of 25μg/kg. Kambaku-taiso-to significantly suppressed the incidence of yawning induced by talipexole. These results suggest that Kambaku-taiso-to exerts a suppressive effect on the incidence of yawning.