The effects of selective dopamine D1 or D2 receptor antagonists on the establishment of agonist-induced place conditioning in rats.

The ability of the dopamine D1 antagonist, SCH 23390 (0.01, 0.1, 1.0, 2.0 mg/kg) or the D2 antagonist, metoclopramide (1.0, 10.0, 20.0 mg/kg), to block the establishment of place conditioning with either the nonselective dopamine agonist, amphetamine (2.0 mg/kg), the D1 agonist, SKF 38393 (10.0 mg/kg), or the D2 agonist, quinpirole (1.0 mg/kg), was evaluated in rats. The experimental protocol consisted of three phases. During the preexposure phase, rats explored two distinctive compartments joined by a small tunnel. During the 8-day conditioning phase, rats were pretreated with either saline, SCH 23390 or metoclopramide; 1 hr later the animals were treated with an agonist and confined to one compartment for 30 min. On alternate days, rats received saline and were placed in the opposite compartment. Test days occurred over the remaining 3 days during which drug-free animals were allowed access to both compartments. A significant increase or decrease in the amount of time spent in the drug-paired environment was indicative of a place preference or aversion, respectively. SCH 23390 and metoclopramide were effective in blocking amphetamine-induced place preference and SKF 38393-induced place aversion. At lower doses, the D1 and D2 antagonist blocked the place preference induced by quinpirole, however, higher doses were not effective. In general, these data suggest that both receptor subtypes participate in the establishment of place conditioning with amphetamine, SKF 38393 or quinpirole.