A ROLE FOR D-2, BUT NOT D-1, DOPAMINE-RECEPTORS IN THE RESPONSE-REINSTATING EFFECTS OF FOOD REINFORCEMENT

Although the reinforcing properties of food are reduced in the presenc e of dopamine antagonist drugs, controversy exists about the relative roles of D-1 vs D-2 receptor subtypes in the actions of these drugs. T he current experiment compared the effects of raclopride (a selective D-2 receptor antagonist) and SCH 39166 (a selective D-1 receptor antag onist) in the response-reinstating effects of food reinforcement. Hung ry rats were trained to run a straight-alley for food reinforcement du ring single daily trials. The operant was then extinguished during con secutive daily non-reinforced trials. Subjects were then injected with one of four doses of raclopride (0.0, 1.0, 0.5, and 0.25 mg/kg, IP) o r SCH 39166 (0.0, 1.0, 0.5, and 0.1 mg/kg IP) 30 min prior to a single reinforced treatment trial. Twenty-four h later, a test trial was con ducted in an unbaited runway. The single reinforced trial in the midst of extinction was observed to reinstate operant runway performance. R aclopride, but not SCH 39166, dose-dependently attenuated this reinsta tement. Motor control groups ruled out the possibility that these resu lts were due to differential residual motor effects of the drugs. Resu lts suggest that D-2, but not D-1, dopamine receptors, are involved in the response-reinstating properties of food reinforcement. (C) 1997 E lsevier Science Inc.