Dopamine's role in learning Pavlovian cues associated with different rates of reward
An animal's ability to thrive in their environment depends on their ability to identify the numerous cues that are associated with earning a reward. While dopamine is involved in Pavlovian conditioning with a single cue-reward relationship, it is unknown how dopamine neurotransmission is involved in the simultaneous learning of multiple cue-reward relationships. To address this question we used a combination of pharmacology and fast scan cyclic voltammetry (FSCV) to examine dopamine release in the nucleus accumbens in rats trained on a Pavlovian conditioning task with two distinct cue-reward relationships. These cues were associated with different rates of reward. The pattern of dopamine release throughout learning strongly related with the electrode placement in either the Nac core, or shell. Pharmacological manipulations also suggest that dopamine is only necessary for the expression of conditioned responding, and not in the learning, or the performance of this task. These results indicate heterogeneity of dopamine release in the nucleus accumbens during Pavlovian conditioning, as well as an unexpected exclusive role of dopamine in the expression of conditioned responding in the task.