Methylxanthine-induced attenuation of pecking in chickens.

1. Apomorphine induced dose-dependent pecking in chickens. 2. The response was decreased by theophylline or caffeine in a dose-dependent manner. 3. Administration of theophylline or caffeine alone did not exert any effect on pecking behaviour. 4. Dipyridamole administration neither induced pecking nor altered the pecking induced by apomorphine. 5. Administration of 5-N-ethylcarboxamide-adenosine to animals caused variable effects on pecking induced by apomorphine. The drug did not induce pecking by itself. 6. It is concluded that the inhibitory response to methylxanthines may be mediated through blockade of adenosine receptors. However, to prove this, more experiments are needed.