Effects of adenosine receptor agonists and antagonists on physostigmine-induced yawning.

The effect of adenosine receptor agonists and antagonists on physostigmine-induced yawning was investigated in intact or cannulated rats. Intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) administration of physostigmine to rats induced yawning dose dependently. I.p. or i.c.v. treatment of the animals with atropine, theophylline, 5-N-ethylcarboxamidoadenosine (NECA) or N6-cyclohexyladenosine reduced the yawning induced by i.p. injection of physostigmine. I.p. administration of theophylline decreased the yawning induced by i.c.v. injection of physostigmine. The inhibitory action of N6-cyclohexyladenosine (i.p.) also was decreased by 8-phenyltheophylline (i.p.) pretreatment. It is concluded that yawning induced by a central cholinergic mechanism and a central adenosine mechanism interacts with the cholinergic-induced behaviour.