The conditioned place preference paradigm was used to examine the role of the D2 receptor in mediating the reinforcing effects of dopamine (DA) agonists. 2. During the 3-day pre-exposure phase, rats explored two distinctive end compartments which were adjoined by a small tunnel. During the 8-day conditioning phase, groups of rats were treated with the selective D2 receptor agonists, quinpirole (0.01, 0.025, 0.05, 0.10, 0.25, 1.0 and 5.0 mg/kg IP) or bromocriptine (0, 0.01, 0.1, 0.5, 1.0, 5.0 and 10.0 mg/kg IP) and confined to one compartment for 30 min. On alternate days, rats received vehicle injections and were placed in the opposite compartment. Test days occurred over the remaining 3 days during which untreated animals explored both compartments. 3. Rats conditioned with quinpirole or bromocriptine showed significant increases in time spent in the drug-paired environment from pre-exposure to test indicating the establishment of conditioned place preferences. 4. This suggests a functional role for the D2 receptor in mediating the rewarding effects of DA agonists.
