Noradrenergic β-receptor antagonism in the basolateral amygdala impairs reconsolidation, but not extinction, of alcohol self-administration: Intra-BLA propranolol impairs reconsolidation of alcohol self-administration.

Abstract

A critical barrier to recovery from alcohol addiction is relapse propensity. Alcohol cues can trigger relapse, and pharmacologically facilitating processes such as extinction, which decreases cue associations, may help prevent relapse. The noradrenergic system mediates extinction learning for alcohol; however, the neural locus of this effect is unknown. This study sought to determine whether the basolateral amygdala (BLA), a region critical for fear extinction, also mediates extinction of alcohol seeking. Hooded Wistar rats (N = 12-15 per experiment) were implanted with bilateral cannula targeting the BLA and trained to lever press for 10% ethanol during auditory or visual cues. Infusions of the β-receptor antagonist propranolol (2 µg/side) were administered prior to extinction (Experiment 1), and rats assessed for relapse-like behaviour two weeks later, thus allowing for spontaneous recovery. We expected intra-BLA propranolol to impair extinction learning; however, propranolol-treated rats exhibited reduced responding in the test of spontaneous recovery, suggesting enhanced extinction. We investigated this unexpected result by determining if propranolol treatment affected memory processes other than extinction. In a subsequent experiment, rats were infused with propranolol immediately after extinction to target consolidation of extinction (Experiment 2a), and assessed for spontaneous recovery. Propranolol was also infused after self-administration to target reconsolidation of the original learning (Experiment 2b). Propranolol treatment had no effect on consolidation of extinction learning, but impaired reconsolidation of self-administration. Propranolol administered prior to a self-administration session did not affect reinforced responding (Experiment 2c). Extinction and reconsolidation are opposing processes triggered by specific test conditions. We suggest our test conditions induced reconsolidation of self-administration memory by propranolol, rather than modulation of extinction. Thus, our data implicates intra-BLA noradrenergic β-receptors in reconsolidation of alcohol self-administration memory.