Acquisition of glucose-conditioned flavor preference requires the activation of dopamine D1-like receptors within the medial prefrontal cortex in rats

In this study, we investigated the role of dopamine transmission within the medial prefrontal cortex (mPFC) in flavor preference learning induced by post-oral glucose. In Experiment 1, rats were trained with a flavor (CS+) paired with intragastric (IG) infusions of 8% glucose and a different flavor (CS-) paired with IG water infusions. The CS+ preference was evaluated in two-bottle tests following bilateral injection of the dopamine D1-like receptor antagonist, SCH23390, into the mPFC at total doses of 0, 12 and 24 nmol. SCH23390 produced dose-dependent reductions in CS+ intake but did not block the CS+ preference. In Experiment 2, new rats were injected daily in the mPFC with either saline or SCH23390 (12 nmol), prior to training sessions with CS+/IG glucose and CS-/IG water. In the two-bottle choice tests, SCH rats, unlike the Control rats, failed to prefer the CS+ (50% vs. 74%). Collectively, the results show that D1-like receptor activation in the medial prefrontal cortex plays a crucial role in the acquisition of flavor preference learning induced by the post-oral reinforcing properties of glucose.