The role of different subregions of the basolateral amygdala in cue-induced reinstatement and extinction of food-seeking behavior.

Reinstatement of previously extinguished instrumental responding for drug-related cues has been used as an animal model for relapse of drug abuse, and is disrupted by inactivation of the basolateral amygdala (BLA). However, the role that the BLA plays in reinstatement induced by cues associated with natural rewards is unclear. The present study assessed the effects of inactivation of different regions of the BLA in cue-induced reinstatement of food-seeking behavior and in the extinction of instrumental responding for food. In experiment 1, rats acquired a lever pressing response for food reward paired with a light/tone conditioned stimulus (CS). They were then subjected to extinction training, where both food and the CS were withheld. Reinstatement of extinguished responding was measured during response-contingent presentations of the CS alone. Following saline infusions into the caudal or rostral BLA, rats displayed a significant increase in lever pressing during reinstatement sessions. Inactivation of these subregions with bupivacaine did not attenuate responding for the CS in the absence of food delivery. In fact, inactivation of the caudal BLA potentiated responding relative to vehicle treatments. Analysis of within-session responding revealed that caudal BLA inactivation retarded extinction of lever pressing in response to the CS. In experiment 2, inactivation of the caudal BLA on the first or second day of extinction training significantly retarded the acquisition of extinction learning on the following day. These data indicate that that the caudal BLA may play a specific role in the extinction of appetitive conditioned responses, by monitoring changes in the reinforcing value of pavlovian conditioned stimuli linked to action-outcome associations once these associations have been formed. Moreover, these findings support a growing body of evidence indicating that separate neural circuits incorporating the BLA may play different roles in mediating reinstatement of reward-seeking behaviors induced by either drug or food related stimuli.