Role of adenosine A2a receptors in the nucleus accumbens.

Adult male mice were stereotaxically implanted with permanent indwelling guide cannulae for bilateral injections into the nucleus accumbens (ACB). The effects on spontaneous locomotor activity of selective agonists for adenosine receptor subtypes were examined following bilateral injections into the ACB. Intra-ACB injections of CGS 21680, a potent and selective agonist at striatal adenosine A2a receptors, elicited pronounced, dose-related reductions in locomotor activity whereas similar bilateral dosages of CPA, a selective agonist at adenosine A1 receptors, did not significantly affect locomotor activity. The pronounced locomotor depression elicited by intra-ACB injections of CGS 21680 were completely blocked by I.P. pretreatment with DMPX, an adenosine receptor antagonist exhibiting selectivity for striatal A2 receptors, at a dosage which alone had no significant effect on locomotor activity. Adenosine A2a receptors in the nucleus accumbens may selectively modulate dopamine-mediated mesolimbic behavioral circuits involved in spontaneous locomotion.