D-2 DOPAMINE-RECEPTOR INVOLVEMENT IN THE ROUGH-AND-TUMBLE PLAY-BEHAVIOR OF JUVENILE RATS

By using dorsal contacts and pinning to quantify play behavior in juve nile rats, it was found that the D-2 agonist, quinpirole, reduced both measures of play at doses greater than 0.05 mg/kg. Eticlopride, a D-2 antagonist, also reduced both measures of play and blocked the reduct ion caused by quinpirole. The effect of quinpirole on play was largely unaffected by concurrent administration of either a D-1 agonist (SKF 38393) or a D-1 antagonist (SCH 23390), suggesting that D-1 and D-2 re ceptors are functionally independent with respect to play behavior. Qu inpirole also reduced overall activity, suggesting that the effects on play may net be selective to neural circuitry responsible for play be havior. Although low doses of quinpirole (0.001-0.03 mg/kg) had a tend ency to increase pinning, this effect was not very robust. These data suggest that D-2 dopamine receptors may not have a major role in the c ontrol of play behavior in juvenile rats.