Reconditioning of heroin place preference requires the basolateral amygdala

To investigate the role of the basolateral amygdala (BLA) in the reacquisition of heroin seeking, we studied the effect of BLA inactivation after heroin re-exposure in the presence of drug-conditioned cues. We employed a heroin conditioned place preference task [Leri F, Rizos Z, 2005. Reconditioning of drug-related cues: a potential contributor to relapse after drug re-exposure. Pharmacol Biochem Behav 2005;80:621-30.], where after initial conditioning and subsequent extinction, rats received a single reconditioning session (explicit compartment-heroin re-pairing), followed by a test of heroin seeking 24 h later. Rats were infused with GABAA/GABAB agonists (muscimol and baclofen, 0.03 and 0.3 nmol, respectively/0.3 μl) or vehicle, either 15 min or 6 h following the heroin reconditioning session. Animals that received vehicle infusions, whether they were given 15 min or 6 h following reconditioning, showed a significant preference for the heroin-paired compartment 24 h later. However, inactivation of the BLA 15 min post-reconditioning, but not 6 h following reconditioning, completely blocked the reacquisition of heroin seeking. These results suggest that the BLA plays an important role in a putative learning process initiated by drug re-exposure which may underlie the process of relapse.