Role of nucleus accumbens dopamine D-1 and D-2 receptors in instrumental and Pavlovian paradigms of conditioned reward

Rationale: This study investigated the role of nucleus accumbens dopamine D -1 and D-2 receptors in two different paradigms of conditioned reward. Obje ctive: We addressed the question whether accumbal dopamine is important for the motor or for the motivational components of reward. Methods: We compar ed the effects of intra-accumbal infusion of the dopamine D-1 receptor anta gonist SCH23390 (0.3, 1.0, 3.0 mu g) and the D-2 receptor antagonist sulpir ide (0.3, 1.0, 3.0 mu g) on conditioned lever pressing for food, with the e ffects on the inhibition of the startle response by a conditioned reward si gnal. Results: Both the D-1 and the D-2 antagonist dose-dependently attenua ted conditioned lever pressing for reward under a fixed-ratio of responding and increased the consumption of freely available lab chow. However, the p reference for freely available pellets, and the attenuation of the startle response in the presence of a conditioned stimulus predicting reward were n ot impaired by blockade of accumbal dopamine receptors. Conclusions: Our da ta support the idea that dopamine in the nucleus accumbens is necessary for instrumental response selection in the context of reward rather than for t he mere motor performance of behavior or for the evaluation of the hedonic properties of rewarding stimuli.