The influence of nitric oxide (NO) on adenosine release was investigated by the push-pull technique in the ventral striatum of the urethane-anaesthetized rat. Superfusion with the NO donor diethylamine-NO enhanced, whereas superfusion with the NO synthase inhibitor L-NG-nitroarginine methyl ester decreased the output of adenosine. The effect of L-NG-nitroarginine methyl ester was abolished by L-arginine methyl ester. These findings indicate that, in the ventral striatum of the rat, NO modulates adenosine release.