Influence of SCH23390 and Spiperone on the Expression of Conditioned Place Preference Induced by d-Amphetamine or Cocaine in the Rat

The present study investigated the effects of selective dopamine D1 and D2 receptor antagonists, SCH23390 and spiperone, on the expression of conditioned place preference (CPP) induced by either d-amphetamine or cocaine. The CPP protocol consisted of three phases: pre-conditioning exploration, conditioning, and a post-conditioning test. The data indicated that CPP was significantly induced by intraperitoneal injection of either d-amphetamine (2 mg/kg) or cocaine (10 mg/kg). The expression of d-amphetamine CPP was significantly inhibited by SCH23390 (0.08, 0.16 mg/kg) and spiperone (0.15 mg/kg) when given alone before the post-conditioning test session. In contrast, such pretreatment to produce antagonistic effects was not observed for cocaine CPP. However, the expression of cocaine CPP was significantly attenuated by a combination of SCH23390 and spiperone administered prior to the test session. These data indicate that the rewarding properties of d-amphetamine and cocaine as expressed under the CPP task may depend upon different neural substrates. The degrees of D1 and D2 receptors involved in mediating the expression of CPP induced by d-amphetamine and cocaine are different.