Nunez, C. | Search bioRxiv

bioRxiv2022

Disentangling the molecular mechanisms underlying the retrieval and extinction of morphine withdrawal-associated memories in the basolateral amygdala and dentate gyrus.

Despite their indisputable efficacy for pain management, opiates prescription remains highly controversial due to their elevated addictive potential. Relapse in drug use is one of the principal problems for addiction treatment, being drug-associated memories among its main triggers. Consequently, the extinction of these memories has been proposed as a useful therapeutic tool. Hence, by using the conditioned place aversion (CPA) paradigm in rats we investigated some of the molecular mechanisms that occurred during the retrieval and extinction of morphine withdrawal memories in the basolateral amygdala (BLA) and the hippocampal dentate gyrus (DG), which control emotional and episodic memories, respectively. The retrieval of aversive memories associated with the abstinence syndrome paralleled with decreased mTOR activity and increased Arc and GluN1 expressions in the DG. Additionally, Arc mRNA levels in this nucleus very strongly correlated with the CPA score exhibited by the opiate-treated rats. On the other hand, despite the unaltered mTOR phosphorylation Arc augmented in the BLA. After the extinction test, Arc and GluN1 expressions raised in both the DG and BLA of control and morphine-treated animals. Remarkably, Homer1 expression in both areas correlated almost perfectly with the extinction showed by morphinedependent animals. Also, Arc expression in the DG correlated strongly with the extinction of the CPA manifested by the group treated with the opiate. Finally, our results support coordinated activity of some of these neuroplastic proteins for the extinction of morphine activity in a regional-dependent manner. Present data provide evidence of differential expression and activity of synaptic molecules during the retrieval and extinction of aversive memories of opiate withdrawal in amygdalar and hippocampal regions that will likely permit the development of therapeutic strategies able to minimize relapses induced by drug-associated aversive memories.

pharmacology and toxicology↗

bioRxiv2021

Distinct regulation of dopamine D3 receptor in the basolateral amygdala and dentate gyrus during the reinstatement of cocaine CPP induced by drug priming and social stress

Relapse in cocaine seeking and intake is one of the main challenges when treating its addiction. Among the triggering factors for recurrence of cocaine use are the re-exposure to the drug and stressful events. Cocaine relapse engages the activity of memory-related nuclei, such as the basolateral amygdala (BLA) and the hippocampal dentate gyrus (DG), which are responsible for emotional and episodic memories. Besides, D3 receptor (D3R) antagonists have recently arisen as a potential treatment for preventing drug relapse. Thus, we have assessed the impact of D3R blockade in the expression of some dopaminergic markers and in the activity of the mTOR pathway, that is modulated by D3R, in the BLA and DG during the reinstatement of cocaine-induced CPP evoked by drug priming and social stress. Reinstatement of cocaine-CPP paralleled with a trend to increase of D3R and dopamine transporter (DAT) levels in the BLA. Social stress-but not drug-induced reactivation of cocaine memories was prevented by systemic administration of SB-277011-A (a selective D3R antagonist), that was able, however, to impede D3R and DAT up-regulation in the BLA during CPP reinstatement evoked by both stress and cocaine. Concomitantly with cocaine-CPP reactivation occurred a diminution of mTOR phosphorylation (activation) in the BLA and DG that was inhibited by D3R blockade in both nuclei before the social stress episode, and only in the BLA when CPP reinstatement was provoked by a cocaine prime. Our data, while support a main role for D3R signalling in the BLA in the reactivation of cocaine memories evoked by social stress, indicates that different neural circuits and signalling mechanisms might mediate in the reinstatement of cocaine-seeking behaviours depending upon the triggering stimuli.

neuroscience↗