The role of the nucleus accumbens OXR1 in cocaine-induced locomotor sensitization

Identification of the circRNA-miRNA-mRNA network for treating methamphetamine-induced relapse and behavioral sensitization with cannabidiol

AIMS

This study aims to investigate the pharmacological effects and the underlying mechanism of cannabidiol (CBD) on methamphetamine (METH)-induced relapse and behavioral sensitization in male mice.

METHODS

The conditioned place preference (CPP) test with a biased paradigm and open-field test were used to assess the effects of CBD on METH-induced relapse and behavioral sensitization in male mice. RNA sequencing and bioinformatics analysis was employed to identify differential expressed (DE) circRNAs, miRNAs, and mRNAs in the nucleus accumbens (NAc) of mice, and the interaction among them was predicted using competing endogenous RNAs (ceRNAs) network analysis.

RESULTS

Chronic administration of CBD (40 mg/kg) during the METH withdrawal phase alleviated METH (2 mg/kg)-induced CPP reinstatement and behavioral sensitization in mice, as well as mood and cognitive impairments following behavioral sensitization. Furthermore, 42 DEcircRNAs, 11 DEmiRNAs, and 40 DEmRNAs were identified in the NAc of mice. The circMeis2-miR-183-5p-Kcnj5 network in the NAc of mice is involved in the effects of CBD on METH-induced CPP reinstatement and behavioral sensitization.

CONCLUSIONS

This study constructed the ceRNAs network for the first time, revealing the potential mechanism of CBD in treating METH-induced CPP reinstatement and behavioral sensitization, thus advancing the application of CBD in METH use disorders.

Use of drug purchase tasks in medications development research: orexin system regulation of cocaine and drug demand

Commodity purchase tasks provide a useful method for evaluating behavioral economic demand in the human laboratory. Recent research has shown how responding to purchase tasks for blinded drug administration can be used to study abuse liability. This analysis uses data from a human laboratory study to highlight how similar procedures may be particularly useful for understanding momentary changes in drug valuation when screening novel interventions. Eight nontreatment-seeking participants with cocaine use disorder (one with partial data) were enrolled in a cross-over, double-blind, randomized inpatient study. Participants were maintained on the Food and Drug Administration-approved insomnia medication suvorexant (oral; 0, 5, 10, 20 mg/day) in randomized order with experimental sessions completed after at least 3 days of maintenance on each suvorexant dose. Experimental sessions included administration of a sample dose of 0, 10 and 30 mg/70 kg intravenous cocaine. Analyses focused on purchase tasks for the blinded sample dose as well as alcohol, cigarettes and chocolate completed 15 min after the sample dose. As expected based on abuse liability, near zero demand was observed for placebo with dose-related increases in cocaine demand. Suvorexant maintenance increased cocaine demand in a dose-related manner with the greatest increase observed for the 10 mg/kg cocaine dose. Increased demand under suvorexant maintenance was also observed for alcohol. No effect of cocaine administration was observed for alcohol, cigarette, or chocolate demand. These data support the validity of demand procedures for measuring blinded drug demand. Findings also parallel self-administration data from this study by showing increases in cocaine use motivation under suvorexant maintenance.

Choline-Sigma-1R as an Additional Mechanism for Potentiation of Orexin by Cocaine

Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX1 and OX2, Gq-coupled GPCRs. We examined the effect of a selective OX1 agonist, OXA (17-33) on cytosolic calcium concentration, [Ca2+]i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca2+]i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX1 receptors antagonist. In Ca2+-free saline, the OXA (17-33)-induced increase in [Ca2+]i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP3) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca2+]i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca2+]i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX1 via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine-orexin A interaction in nucleus accumbens neurons.

The orexin (hypocretin) neuropeptide system is a target for novel therapeutics to treat cocaine use disorder with alcohol coabuse

An estimated 50-90% of individuals with cocaine use disorder (CUD) also report using alcohol. Cocaine users report coabusing alcohol to 'self-medicate' against the negative emotional side effects of the cocaine 'crash', including the onset of anxiety. Thus, pharmaceutical strategies to treat CUD would ideally reduce the motivational properties of cocaine, alcohol, and their combination, as well as reduce the onset of anxiety during drug withdrawal. The hypothalamic orexin (hypocretin) neuropeptide system offers a promising target, as orexin neurons are critically involved in activating behavioral and physiological states to respond to both positive and negative motivators. Here, we seek to describe studies demonstrating efficacy of orexin receptor antagonists in reducing cocaine, alcohol- and stress-related behaviors, but note that these studies have largely focused on each of these phenomena in isolation. For orexin-based compounds to be viable in the clinical setting, we argue that it is imperative that their efficacy be tested in animal models that account for polysubstance use patterns. To begin to examine this, we present new data showing that rats' preferred level of cocaine intake is significantly increased following chronic homecage access to alcohol. We also report that cocaine intake and motivation are reduced by a selective orexin-1 receptor antagonist when rats have a history of cocaine + alcohol, but not a limited history of cocaine alone. In light of these proof-of-principle data, we outline what we believe to be the key priorities going forward with respect to further examining the orexin system in models of polysubstance use. This article is part of the special issue on Neurocircuitry Modulating Drug and Alcohol Abuse.