Opposing roles of D1 and D2 receptors in appetitive conditioning.

Previous studies have shown that D(1) receptor blockade disrupts and D(2) receptor blockade enhances long-term potentiation. These data lead to the prediction that D(1) antagonists will attenuate and D(2) antagonists will potentiate at least some types of learning. The prediction is difficult to test, however, because disruptions in either D(1) or D(2) transmission lead to reduced locomotion, exploration, and response execution and are therefore likely to impair learning that requires behavioral responding (including exploration of an environment) during the learning episode.