Contribution of ventral tegmental area dopamine neurons to expression of conditional fear: effects of electrical stimulation, excitotoxin lesions, and quinpirole infusion on potentiated startle in rats.

Potentiated startle was used in this study to determine the fear-motivational functions of the ventral tegmental area (VTA). In Experiment 1, electrical stimulation of the VTA increased acoustic startle amplitudes. In subsequent experiments fear-potentiated startle was assessed following axon-sparing N-methyl-D-aspartic acid (NMDA) lesions of the VTA and after bilateral intra-VTA infusion of the dopamine (DA) D2/3 receptor agonist quinpirole. The NMDA lesions produced substantial cell loss in the medial ventral tegmentum and suppressed fear expression. Similarly, inhibition of DA neuronal activity associated with locally administered quinpirole blocked fear-potentiated startle. It was suggested that VTA neurons and their forebrain DA projections regulate levels of aversive emotional arousal within the amygdala-based fear system.