Inhibition of the mesoamygdala dopaminergic pathway impairs the retrieval of conditioned fear associations

Previous findings have demonstrated that systemic dopaminergic manipulation s impair the retrieval of Pavlovian conditioned fear. A second-order fear-c onditioning paradigm was used to test whether the dopaminergic projection f rom the ventral tegmental area (VTA) to the lateral and basal amygdala (LBA ) can affect conditioned fear. Phase I entailed conditioned stimulus-uncond itioned stimulus (CSI-US) pairings. In Phase 2, drugs were infused in eithe r the LBA or VTA prior to pairings of CS2 (a second cue) with CS1. In Phase 3, freezing behavior elicited by CS2 was tested without drugs. Infusions o f the D2 agonist quinpirole into the VTA or of the D1 antagonist SCH 23390 into the LBA caused a decrease in freezing to CS2. Both manipulations decre ase DI receptor activation in the LBA. Infusions of the D1 agonist SKF 3839 3 into the LBA had no effect. This pattern of results is consistent with th e hypothesis that the VTA-LBA dopaminergic projection modulates the retriev al of an association between a CS and footshock US.