Involvement of protein phosphatases in the destabilization of methamphetamine-associated contextual memory.

Abstract

Destabilization refers to a memory that becomes unstable when reactivated and is susceptible to disruption by amnestic agents. Here we delineated the cellular mechanism underlying the destabilization of drug memory. Mice were conditioned with methamphetamine (MeAM) for 3 d, and drug memory was assessed with a conditioned place preference (CPP) protocol. Anisomycin (ANI) was administered 60 min after the CPP retrieval to disrupt reconsolidation. We found that destabilization of MeAM CPP after the application of ANI was blocked by the N-methyl-d-aspartate receptor (NMDAR) antagonist MK-801 and the NR2B antagonist ifenprodil (IFN) but not by the NR2A antagonist NVP-AAM077 (NVP). In addition, decrease in the phosphorylation of GluR1 at Serine845 (p-GluR1-Ser845), decrease in spine density, and a reduction in the AMPAR/NMDAR ratio in the basolateral amygdala (BLA) were reversed after the MK-801 treatment. The effect of ANI on destabilization was prevented by the protein phosphatase 2B (calcineurin, CaN) inhibitors cyclosporine A (CsA) and FK-506 and the protein phosphatase 1 (PP1) inhibitors calyculin A (CA) and okadaic acid (OA). These results suggest that memory destabilization involves the activation of NR2B-containing NMDARs, which in turn allows the influx of Ca2+. Increased intracellular Ca2+ stimulates CaN, leading to the dephosphorylation and inactivation of inhibitor 1 and the activation of PP1. PP1 then dephosphorylates p-GluR1-Ser845 to elicit AMPA receptor (AMPAR) endocytosis and destabilization of the drug memory.