Amygdaloid D sub(1) dopamine receptor involvement in Pavlovian fear conditioning

• Published in: Brain research 1999-05, Vol.827 (1-2), p.28-40
• Main Authors: Guarraci, F A, Frohardt, R J, Kapp, B S
• Format: Article
• Language: English
• ISSN: 0006-8993

The amygdala has long been implicated in conditioned fear. The mesencephalic dopaminergic system provides a rich innervation to the amygdala Specific activation of the mesoamygdaloid dopaminergic system has been reported to occur in response to conditioned fear-arousing stimuli suggesting that dopamine release in the amygdala may contribute to the acquisition and/or expression of conditioned fear. Using a 2 x 2 factorial design, Experiment 1A investigated the effects of bilateral intra-amygdaloid infusions of the selective D sub(1) receptor antagonist, SCH 23390 (2.0 mu g 0.5 mu l super(-1) side super(-1)), on the acquisition and expression of Pavlovian conditioned fear measured by freezing to acoustic and background contextual stimuli. Infusions of SCH 23390 prior to acquisition training, prior to retention testing or prior to both significantly attenuated conditioned freezing during retention testing. Experiment 1B investigated the dose-dependent effects of pre-training infusions of SCH 23390 (0.5, 1.0 and 2.0 mu g) on conditioned fear. Pre-training infusions of SCH 23390 dose-dependently attenuated conditioned freezing during retention testing. Experiment 2A investigated the effects of bilateral infusions of the selective D sub(1) receptor agonist, SKF 82958 (2.0 mu g 0.5 mu l super(-1) side super(-1)) on the acquisition and expression of conditioned fear. Infusions of SKF 82958 prior to training facilitated conditioned freezing during retention testing. Experiment 2B investigated the dose-dependent effects of pre-training infusions of SKF 82958 (1.0, 2.0 and 4.0 mu g) on conditioned fear. Pre-training infusions of SKF 82958 dose-dependently facilitated conditioned freezing during retention testing. In conclusion, these results suggest that dopamine transmission within the amygdala contributes to the acquisition and expression of Pavlovian fear conditioning.