Background: Dopamine signaling in the nucleus accumbens (NAc) is essential for goal-directed behaviors and primarily arises from burst firing of ventral tegmental area neurons. However, the role of associative neural substrates such as the basolateral amygdala (BLA) in regulating phasic dopamine release in the NAc, particularly during reward seeking, remains unknown.
Methods: Male Sprague-Dawley rats learned to discriminate two cues: a discriminative stimulus (DS) that predicted sucrose reinforcement contingent upon a lever press and a nonassociated stimulus (NS) that predicted a second lever never reinforced with sucrose. Following training, a test session was completed in which NAc dopamine was measured using fast-scan cyclic voltammetry in conjunction with inactivation of the ipsilateral BLA (gamma-aminobutyric acid agonists; baclofen/muscimol) to determine the contribution of BLA activity to dopamine release in the NAc core during the task.
Results: Under vehicle conditions, DS and NS presentation elicited dopamine release within the NAc core. The DS evoked significantly more dopamine than the NS. Inactivation of the BLA selectively attenuated the magnitude of DS-evoked dopamine release, concurrent with an attenuation of DS-evoked conditioned approaches. Other behavioral responses (e.g., lever pressing) and dopamine release concomitant with those events were unaltered by BLA inactivation. Furthermore, neither ventral tegmental area electrically stimulated dopamine release nor the probability of high concentration dopamine release events was altered following BLA inactivation.
Conclusions: These results demonstrate that the BLA terminally modulates dopamine signals within the NAc core under specific, behaviorally relevant conditions, illustrating a functional mechanism by which the BLA selectively facilitates responding to motivationally salient environmental stimuli.
Copyright 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.