The effect of adenosine receptor ligands on dizocilpine-induced locomotion was studied in mice. Dizocilpine-induced hyperactivity (0.1 mg/kg i.p.) in mice was antagonized by all adenosine receptor agonists: CPA--A1 receptor agonist, CGS 21680--A2 receptor agonist, and NECA--A1/A2 receptor agonist, but the effect of NECA was the most apparent. Locomotion induced by the threshold dose of dizocilpine (0.05 mg/kg i.p.) was enhanced by DPMX (A2A adenosine receptor antagonist) and by the theophylline (A1 and A2 receptor antagonist), but not by A1 receptor antagonist--CPT. These data suggest that adenosinergic system is involved in the mechanism of dizocilpine-induced hyperactivity, and it seems that A2A adenosine receptor plays a more important role.