Calcineurin Promotes Neuroplastic Changes in the Amygdala Associated with Weakened Cocaine-Cue Memories.

Interfering with memory reconsolidation or inducing memory extinction are two approaches for weakening maladaptive memories in disorders such as addiction and post-traumatic stress disorder. Both extinction and reconsolidation are regulated by intracellular protein kinases and phosphatases, and interfering with these signaling molecules can alter memory strength. The calcium-dependent protein phosphatase, calcineurin (CaN), has been implicated in both the consolidation and extinction of fear memories. However, the role of CaN in regulating drug-cue associative memories has not been investigated. Prior studies have demonstrated that plasticity at thalamo-lateral amygdala (T-LA) synapses is critically involved in the regulation of cocaine-cue memories. Therefore, in the present study, we tested the effects of LA administration of an activator of CaN, chlorogenic acid (CGA), on behavioral and electrophysiological indices of cocaine cue memory reconsolidation and extinction. Male, Sprague-Dawley rats were trained to self-administer cocaine paired with an audiovisual cue. The cue memory was then either briefly reactivated, extinguished, or not manipulated, followed immediately by LA infusion of CGA. Rats were tested 24 h later for cue-induced reinstatement, or LA slices were prepared for electrophysiological recordings. We found that intra-LA infusions of CGA following cue extinction or reconsolidation reduced cue-induced reinstatement, which was blocked by co-infusion of the CaN inhibitor, FK-506. Similarly, CGA infusions following cue re-exposure significantly attenuated EPSC amplitude at T-LA synapses, suggesting that CaN affects cocaine-cue memory reconsolidation and extinction by altering T-LA synaptic strength. Therefore, CaN signaling in the LA may represent a novel target for disrupting cocaine-associated memories to reduce relapse.SIGNIFICANCE STATEMENT Repetitive drug use induces synaptic plasticity that underlies the formation of long-lasting associative memories for environmental cues paired with the drug. We previously identified thalamo-amygdala synapses (T-LA) that project via the interal capsule, as an important locus for the regulation of cocaine-cue memories. These synapses are strengthened by repeated cocaine-cue pairings, but this is reversed by extinction training or by optogenetic induction of in vivo long-term depression (LTD). Here, we demonstrate that activating calcineurin, a calcium-dependent phosphatase, following the reactivation or extinction of a cocaine-cue memory, induces LTD-like changes at T-LA synapses, and a corresponding decrease in cue-induced reinstatement, suggesting that calcineurin may be a potential therapeutic target for relapse prevention.