Peripheral and intraamygdalar administration of the dopamine D1 receptor antagonist SCH 23390 blocks fear-potentiated startle but not shock reactivity or the shock sensitization of acoustic startle.

Central dopamine (DA) activity is thought to play a role in fear motivation. The aim of the present study was to assess the involvement of DA D1 receptors in emotional learning. The authors report that peripheral and intraamygdalar administration of the specific D1 receptor antagonist SCH 23390 blocked the acquisition of fear-potentiated startle. Analysis of shock reactivity during footshock administration revealed that the learning impairment could not be explained by a diminution in the aversive properties of the unconditioned stimulus. Additionally, systemic and intraamygdalar injection of SCH 23390 did not alter fear expression as measured with the shock sensitization of acoustic startle. The potential contribution of mesoamygdaloid DA to the acquisition and retrieval of conditioned fear responses is discussed.