Activation or frustration of anti-tumor responses by T-cell-based immune modulation

Cataleptogenic effects of haloperidol (1 mg/kg i.p.) in rats was antagonized by caffeine and theophylline (10-50 mg/kg i.p.), and by selective adenosine A2 receptor antagonist (3,7-dimethyl-1-propargylxanthine) (3 and 6 mg/kg i.p.). Selective A1-adenosine receptor antagonist (8-cyclopentyltheophylline) (1.5 and 3 mg/kg i.p.) was not able to reduce this effect of haloperidol. These results confirm the antagonistic interaction between adenosine A2A and dopamine D2 receptors, and suggest the involvement of adenosine A2 receptors in the mechanisms of catalepsy.