The effects of intra-amygdaloid infusions of a D-sub-2 dopamine receptor antagonist on Pavlovian fear conditioning.

The present study examined the effects of bilateral intra-amygdaloid infusions of the D2 receptor antagonist, eticlopride, on the acquisition and expression of Pavlovian fear conditioning as measured by freezing to acoustic and background contextual stimuli in the rat. Infusions of eticlopride before acquisition or before both acquisition and retention testing significantly attenuated conditioned freezing to tone presentations during the retention test 24 hr later. No effects, however, were observed on freezing that emerged during acquisition. Furthermore, these effects were not attributable to state-dependent learning effects or alterations in baseline activity or shock reactivity. In conclusion, these results suggest that amygdaloid dopamine transmission at D2 receptors contributes to the formation and/or consolidation of fear memories.