Effects of adenosine drugs on apomorphine-induced licking in rats.

1. In the present work, the effect of adenosine agonists and antagonists on apomorphine-induced licking has been studied. 2. Subcutaneous (s.c.) injection of apomorphine (0.125, 0.25 and 0.5 mg/kg) produced dose-dependent licking in rats. 3. Adenosine agonists 5'-N-ethylcarboxamide-adenosine (NECA) and N6-cyclohexyladenosine (CHA) decreased or increased the apomorphine response respectively. 4. Adenosine antagonists theophylline and 8-phenyltheophylline (8-PT) decreased the response induced by apomorphine. Potentiation of licking induced by CHA was decreased by 8-PT pretreatment. 5. It is concluded that adenosine receptors may be involved in the licking behaviour.