Place preference conditioning reveals the involvement of D1-dopamine receptors in the motivational properties of mu- and kappa-opioid agonists.

The role of D1 dopamine receptors in mediating the motivational properties of opioid agonists was investigated by use of place preference conditioning. Administration of the D1 receptor antagonist SCH 23390 (0.001-0.5 mg/kg) or the kappa-opioid receptor agonist U-69593 (0.16 mg/kg) produced conditioned place aversions. In contrast, the mu-opioid agonist, morphine (3.0 mg/kg) was appetitively reinforcing. Chronic infusion of SCH 23390 (1.0 mg/kg/day) during conditioning abolished the effects of both opioid agonists. These data demonstrate the specific involvement of D1 receptors in the motivational properties of mu- and kappa-opioid agonists and suggest that dopaminergic systems are crucial for the expression of both reinforcing and aversive motivational states.