Modulation of methamphetamine memory reconsolidation by neural projection from basolateral amygdala to nucleus accumbens

Greater fatigue, disturbed sleep, persistent memory problems, and reduced CD4+ T cell and B cell percentages in adults with a history of methamphetamine dependence

Methamphetamine (MA) dependence is associated with immunotoxicity and high rates of neuropsychiatric impairments that persist into remission. Although there are currently no FDA-approved pharmacotherapies for MA use disorders, preclinical and clinical studies are beginning to test interventions that directly impact immune signaling. This study was conducted to investigate the relative contribution of immune cell function to the neuropsychiatric sequelae associated with MA dependence and remission. Participants were enrolled into the following study groups: i) control (CTL) group (n = 62): adults with no lifetime history of dependence on any substance other than nicotine or caffeine; and ii) MA group (n = 98) [MA-remission group (n = 55): adults in remission ≥1 month and ≤ 6 months and MA-active group (n = 43): adults actively using MA and meeting criteria for MA dependence]. Participants completed a clinical interview, urine drug analysis, blood sample collection, and questionnaires. Peripheral blood mononuclear cells were analyzed by flow cytometry. Results suggest that early remission from MA dependence is associated with increased fatigue and persistent sleep and prospective and retrospective memory problems, along with reduced B and CD4+ T cell percentages, compared to the CTL group. Preliminary findings support the hypothesis that the immune system modulates the sleep impairments associated with drug actions and provide implications for future research studies and treatment approaches.

Cell-type specific epigenetic and transcriptional mechanisms in substance use disorder

Substance use disorder (SUD) is a chronic and relapse-prone neuropsychiatric disease characterized by impaired brain circuitry within multiple cell types and neural circuits. Recent advancements in single-cell transcriptomics, epigenetics, and neural circuit research have unveiled molecular and cellular alterations associated with SUD. These studies have provided valuable insights into the transcriptional and epigenetic regulation of neuronal and non-neuronal cells, particularly in the context of drug exposure. Critical factors influencing the susceptibility of individuals to SUD include the regulation of gene expression during early developmental stages, neuroadaptive responses to psychoactive substances, and gene-environment interactions. Here we briefly review some of these mechanisms underlying SUD, with an emphasis on their crucial roles in in neural plasticity and maintenance of addiction and relapse in neuronal and non-neuronal cell-types. We foresee the possibility of integrating multi-omics technologies to devise targeted and personalized therapeutic strategies aimed at both the prevention and treatment of SUD. By utilizing these advanced methodologies, we can gain a deeper understanding of the fundamental biology of SUD, paving the way for more effective interventions.

NMDA-induced lesions of the nucleus accumbens core increase the innately rewarding saccharin solution intake and methamphetamine-induced conditioned place preference but not conditioned taste aversion in rats

The role of the nucleus accumbens (NAc) core in determining the valence of innately rewarding saccharin solution intake, methamphetamine (MAMPH)-induced conditioned taste aversion (CTA), and conditioned place preference (CPP) reward remains unclear. The present study utilized the "pre- and post-association" experimental paradigm (2010) to test whether the rewarding and aversive properties of MAMPH can be modulated by an N-methyl-D-aspartic acid (NMDA) lesion in the NAc core. Moreover, it tested how an NAc core NMDA lesion affected the innate reward of saccharin solution intake. The results demonstrate that MAMPH could simultaneously induce an aversive CTA and a rewarding CPP effect, supporting the paradoxical effect hypothesis of abused drugs, in particular amphetamine. Meanwhile, the NMDA-lesioned NAc core increased the reward effect of CPP but did not alter the aversive CTA effect. The NAc core NMDA lesion also enhanced the innate reward of saccharin solution intake. The NAc core therefore seemingly plays an inhibitory role in the innate reward of saccharin solution intake and in the CPP effect. The paradoxical effect hypothesis of abused drugs provides some explanations for the present data in the case of MAMPH administrations. The NAc core may play an essential role in modulating the rewarding but not the aversive properties of MAMPH. The present findings could contribute to the understanding and eventual advancement of clinical interventions for drug addiction and the development of novel pharmacological treatments.

Dorsal raphe to basolateral amygdala corticotropin-releasing factor circuit regulates cocaine-memory reconsolidation

Environmental stimuli elicit drug craving and relapse in cocaine users by triggering the retrieval of strong cocaine-related contextual memories. Retrieval can also destabilize drug memories, requiring reconsolidation, a protein synthesis-dependent storage process, to maintain memory strength. Corticotropin-releasing factor (CRF) signaling in the basolateral amygdala (BLA) is necessary for cocaine-memory reconsolidation. We have hypothesized that a critical source of CRF in the BLA is the dorsal raphe nucleus (DR) based on its neurochemistry, anatomical connectivity, and requisite involvement in cocaine-memory reconsolidation. To test this hypothesis, male and female Sprague-Dawley rats received adeno-associated viruses to express Gi-coupled designer receptors exclusively activated by designer drugs (DREADDs) selectively in CRF neurons of the DR and injection cannulae directed at the BLA. The rats were trained to self-administer cocaine in a distinct environmental context then received extinction training in a different context. Next, they were briefly re-exposed to the cocaine-predictive context to destabilize (reactivate) cocaine memories. Intra-BLA infusions of the DREADD agonist deschloroclozapine (DCZ; 0.1 mM, 0.5 µL/hemisphere) immediately after memory reactivation attenuated cocaine-memory strength, relative to vehicle infusion. This was indicated by a selective, DCZ-induced and memory reactivation-dependent decrease in drug-seeking behavior in the cocaine-predictive context in DREADD-expressing males and females at test compared to respective controls. Notably, BLA-projecting DR CRF neurons that exhibited increased c-Fos expression during memory reconsolidation co-expressed the glutamatergic neuronal marker, vesicular glutamate transporter 3. Together, these findings suggest that the DRCRF → BLA circuit is engaged to maintain cocaine-memory strength after memory destabilization, and this phenomenon may be mediated by DR CRF and/or glutamate release in the BLA.

Dorsal Raphe to Basolateral Amygdala Corticotropin-Releasing Factor Circuit Regulates Cocaine-Memory Reconsolidation

Environmental stimuli elicit drug craving and relapse in cocaine users by triggering the retrieval of strong cocainerelated contextual memories. Retrieval can also destabilize drug memories, requiring reconsolidation, a protein synthesis-dependent storage process, to maintain memory strength. Corticotropin-releasing factor (CRF) signaling in the basolateral amygdala (BLA) is necessary for cocainememory reconsolidation. We have hypothesized that a critical source of CRF in the BLA is the dorsal raphe nucleus (DR) based on its neurochemistry, anatomical connectivity, and requisite involvement in cocaine-memory reconsolidation. To test this hypothesis, male and female Sprague-Dawley rats received adeno-associated viruses to express Gi-coupled designer receptors exclusively activated by designer drugs (DREADDs) selectively in CRF neurons of the DR and injection cannulae directed at the BLA. The rats were trained to self-administer cocaine in a distinct environmental context then received extinction training in a different context. They were then briefly reexposed to the cocaine-predictive context to destabilize (reactivate) cocaine memories. Intra-BLA infusions of the DREADD agonist deschloroclozapine (DCZ; 0.1 mM, 0.5 μL/hemisphere) after memory reactivation attenuated cocaine-memory strength, relative to vehicle infusion. This was indicated by a selective, DCZ-induced and memory reactivation-dependent decrease in drug-seeking behavior in the cocaine-predictive context in DREADD-expressing males and females at test compared to respective controls. Notably, BLA-projecting DR CRF neurons that exhibited increased c-Fos expression during memory reconsolidation co-expressed glutamatergic and serotonergic neuronal markers. Together, these findings suggest that the DRCRF → BLA circuit is engaged to maintain cocaine-memory strength after memory destabilization, and this phenomenon may be mediated by DR CRF, glutamate, and/or serotonin release in the BLA.

Restoring GABAB receptor expression in the ventral tegmental area of methamphetamine addicted mice inhibits locomotor sensitization and drug seeking behavior

Repeated exposure to psychostimulants such as methamphetamine (METH) induces neuronal adaptations in the mesocorticolimbic dopamine system, including the ventral tegmental area (VTA). These changes lead to persistently enhanced neuronal activity causing increased dopamine release and addictive phenotypes. A factor contributing to increased dopaminergic activity in this system appears to be reduced GABAB receptor-mediated neuronal inhibition in the VTA. Dephosphorylation of serine 783 (Ser783) of the GABAB2 subunit by protein phosphatase 2A (PP2A) appears to trigger the downregulation GABAB receptors in psychostimulant-addicted rodents. Therefore, preventing the interaction of GABAB receptors with PP2A using an interfering peptide is a promising strategy to restore GABAB receptor-mediated neuronal inhibition. We have previously developed an interfering peptide (PP2A-Pep) that inhibits the GABAB receptors/PP2A interaction and thereby restores receptor expression under pathological conditions. Here, we tested the hypothesis that restoration of GABAB receptor expression in the VTA of METH addicted mice reduce addictive phenotypes. We found that the expression of GABAB receptors was significantly reduced in the VTA and nucleus accumbens but not in the hippocampus and somatosensory cortex of METH-addicted mice. Infusion of PP2A-Pep into the VTA of METH-addicted mice restored GABAB receptor expression in the VTA and inhibited METH-induced locomotor sensitization as assessed in the open field test. Moreover, administration of PP2A-Pep into the VTA also reduced drug seeking behavior in the conditioned place preference test. These observations underscore the importance of VTA GABAB receptors in controlling addictive phenotypes. Furthermore, this study illustrates the value of interfering peptides targeting diseases-related protein-protein interactions as an alternative approach for a potential development of selective therapeutic interventions.