Disrupting reconsolidation of conditioned withdrawal memories in the basolateral amygdala reduces suppression of heroin seeking in rats

Abstract

Recent data from our laboratory have demonstrated that appetitive drug memories undergo protein synthesis-dependent reconsolidation in the basolateral amygdala (BLA), an area important in the formation of emotional memories. We here investigated the importance of the BLA in the reconsolidation of opiate conditioned withdrawal memories. Rats with bilateral cannulas implanted in the BLA were trained to respond for heroin (0.12 mg/kg, i.v.) under a seeking-taking schedule, which required responding on a seeking lever to gain the opportunity to self-administer heroin by a single response on a taking lever. After induction of opiate dependence with subcutaneously implanted, heroin-filled osmotic minipumps (3 mg x kg(-1) x d(-1) heroin), rats received five consecutive pairings of a conditioned stimulus (CS) (tone, light, and odor compound) paired with naloxone (0.10 mg/kg, s.c.)-precipitated withdrawal. We replicated our previous findings that heroin seeking is suppressed in the presence of the withdrawal-associated CS. However, infusion of Zif268 antisense oligodeoxynucleotide into the BLA before reactivation of the CS-withdrawal association abolished this conditioned suppression in a reactivation-dependent manner. We also report that reconsolidation of CS-withdrawal memories upregulates Zif268 protein in the basolateral but not central nucleus of the amygdala and that Zif268 knockdown occurs selectively in the BLA. These results demonstrate that drug withdrawal memories undergo protein synthesis-dependent reconsolidation in the BLA and suggest a common mechanism for the reconsolidation of both appetitive and aversive drug memories.

Figure 1.

BLA cannulations. Schematic representation of the amygdala at five different rostrocaudal planes. Numbers represent the posterior coordinate from bregma (in millimeters). Injector tips for each cannulation are represented by filled circles.

Figure 2.

Intra-BLA Zif268 ASOs impairs conditioned suppression to a CS previously associated with naloxone-precipitated withdrawal. Bars represent the mean ± SEM suppression ratio of heroin-seeking responses [CS On/(CS On + CS Off); suppression ratio of 0.5 represents no suppression and <0.5 indicates CS-induced suppression] before reactivation, after reactivation, and in a non-reactivated control group. Infusion of Zif268 ASOs impaired subsequent conditioned suppression of heroin seeking relative to both control MSO infusions and baseline pre-reactivation levels. Reconsolidation of the conditioned withdrawal memories is reactivation dependent: animals that did not receive reactivation with the CS, but did receive ASO infusions, showed no difference in suppression ratios compared with MSO-infused controls. *p < 0.05

Figure 3.

A, Zif268 protein levels after reexposure to a conditioned withdrawal stimulus. Zif268 protein was upregulated 2 h after stimulus reexposure in the BLA but not in the CeN; p < 0.05. Data are presented as mean ± SEM. B, Zif268 protein levels after reexposure to a conditioned withdrawal stimulus and Zif268 ASO infusion. Zif268 ASOs resulted in a significant decrease in Zif268 expression compared with rats infused with Zif268 MSOs, 2 h after stimulus reexposure in the BLA but not in the CeN; p < 0.05. Data are presented as mean ± SEM.