Bidirectional Modulation of Alcohol-Associated Memory Reconsolidation through Manipulation of Adrenergic Signaling.

Alcohol addiction is a problem of great societal concern, for which there is scope to improve current treatments. One potential new treatment for alcohol addiction is based on disrupting the reconsolidation of the maladaptive Pavlovian memories that can precipitate relapse to drug-seeking behavior. In alcohol self-administering rats, we investigated the effects of bidirectionally modulating adrenergic signaling on the strength of a Pavlovian cue-alcohol memory, using a behavioral procedure that isolates the specific contribution of one maladaptive Pavlovian memory to relapse, the acquisition of a new alcohol-seeking response for an alcohol-associated conditioned reinforcer. The ß-adrenergic receptor antagonist propranolol, administered in conjunction with memory reactivation, persistently disrupted the memory that underlies the capacity of a previously alcohol-associated cue to act as a conditioned reinforcer. By contrast, enhancement of adrenergic signaling by administration of the adrenergic prodrug dipivefrin at reactivation increased the strength of the cue-alcohol memory and potentiated alcohol seeking. These data demonstrate the importance of adrenergic signaling in alcohol-associated memory reconsolidation, and suggest a pharmacological target for treatments aiming to prevent relapse through the disruption of maladaptive memories.

Antagonism at NMDA receptors, but not ß-adrenergic receptors, disrupts the reconsolidation of pavlovian conditioned approach and instrumental transfer for ethanol-associated conditioned stimuli.

RATIONALE: Reconsolidation is the process by which memories require restabilisation following destabilisation at retrieval. Since even old, well-established memories become susceptible to disruption following reactivation, treatments based upon disrupting reconsolidation could provide a novel form of therapy for neuropsychiatric disorders based upon maladaptive memories, such as drug addiction. Pavlovian cues are potent precipitators of relapse to drug-seeking behaviour and influence instrumental drug seeking through at least three psychologically and neurobiologically distinct processes: conditioned reinforcement, conditioned approach (autoshaping) and conditioned motivation (pavlovian-instrumental transfer or PIT). We have previously demonstrated that the reconsolidation of memories underlying the conditioned reinforcing properties of drug cues depends upon NMDA receptor (NMDAR)- and ß-adrenergic receptor (ßAR)-mediated signalling. However, it is unknown whether the drug cue memory representations underlying conditioned approach and PIT depend upon the same mechanisms. OBJECTIVES: Using orally self-administered ethanol as a reinforcer in two separate experiments, we investigated whether the reconsolidation of the memories underlying conditioned approach and PIT requires ßAR- and NMDAR-dependent neurotransmission. RESULTS: For ethanol self-administering but non-dependent rats, the memories underlying conditioned approach and PIT for a pavlovian drug cue were disrupted by the administration of the NMDAR antagonist MK-801, but not the administration of the ßAR antagonist propranolol, when given in conjunction with memory reactivation. CONCLUSIONS: As for natural reinforcers, NMDARs are required for the reconsolidation of all aspects of pavlovian drug memories, but ßARs are only required for the memory representation underlying conditioned reinforcement. These results indicate the potential utility of treatments based upon disrupting cue-drug memory reconsolidation in preventing relapse.