Involvement of adenosine A1 receptors in antitussive effect in mice.

The effects of N6-cyclohexyladenosine, a selective adenosine A1 receptor agonist, on the capsaicin-induced cough reflex in mice were examined. I.c.v. administration of N6-cyclohexyladenosine in doses that ranged from 0.03 to 0.3 nmol decreased the number of coughs in a dose-dependent manner. Pretreatment with 8-cyclopentyl-1,3-theophylline, a selective adenosine A1 receptor antagonist, significantly reduced the antitussive effect of N6-cyclohexyladenosine. On the other hand, CGS21680 (0.3 and 1 nmol, i.c.v.), a selective adenosine A2 receptor agonist, had no significant effect on the number of capsaicin-induced coughs. These data suggest that adenosine A1 agonists may have a marked antitussive effect in mice.