The transition to compulsion in addiction

Development and validation of the Compulsive Substance Use Questionnaire: Attending to substance use automaticity, craving, and continued use despite negative consequences

BACKGROUND

Compulsivity characterizes an important subtype of substance use disorders (SUDs), but there has been variability in how compulsive substance use is defined and measured. The current study was designed to (1) develop a new measure of substance use compulsivity, (2) validate this scale in a community sample of adults who drink alcohol, and (3) evaluate the association between this new measure of compulsivity and substance use severity. We hypothesize that compulsivity will be characterized by automaticity, craving and insensitivity to negative consequences, and greater substance use severity will be associated with higher levels of substance use compulsivity.

METHODS

A preliminary set of items were generated for the novel Compulsive Substance Use Questionnaire (CSUQ) to reflect three conceptual aspects of substance use compulsivity: automaticity, craving, and disregarding negative consequences. The study recruited a total of 253 adults who drink alcohol, with a range of severity. Participants answered online surveys on compulsivity, frequency of alcohol use, craving, and negative consequences of alcohol use.

RESULTS

We obtained a single-factor solution with 22 items that included 3 automaticity items, 10 craving items, and 9 disregarding negative consequences items. The resulting measure had excellent internal consistency (α = 0.96). The CSUQ was associated with substance use severity; specifically, greater compulsivity was associated with heavy alcohol use and higher frequency of negative consequences associated with alcohol use.

CONCLUSIONS

The current study supports the validity of a new measure of substance use compulsivity, composed of items that closely hew to the concept of substance use compulsivity. Future work investigating compulsivity in other substance use populations with varying levels of severity will further our understanding of compulsive substance use and SUD subtypes.

Beyond the Surface: Deep TMS Efficacy in Reducing Craving in Addictive Disorders. A Systematic Review and Meta-analysis

BACKGROUND

Substance use disorders (SUDs) and Gambling Disorder (GD) are addictive diseases with a chronic course. Due to the limited efficacy of conventional treatments, there is growing interest in alternative approaches targeting the altered neural circuits underlying these disorders. Deep Transcranial Magnetic Stimulation (dTMS) has emerged as a promising neuromodulation technique capable of reaching deep and bilateral brain regions. However, no definite recommendation for its use in addiction treatment exists. This study systematically reviewed and quantitatively analyzed dTMS effects in SUDs and GD.

METHODS

Following the PRISMA guidelines, we screened four electronic databases up to February 2024 and selected relevant English-written original research articles. Seventeen papers were included in the systematic review. As only a minority of studies employed a sham-controlled design, we ran the meta-analysis on a subset of 12 studies, computing the pre-post real stimulation standardized mean change (SMCC) as the effect size, using self-reported craving scores as the dependent variable.

RESULTS

The results showed a significant and large effect of real dTMS in reducing craving scores (SMCC = - 1.26, 95% CI [-1.67, - 0.86], p <.001). High heterogeneity across studies was found at both quantitative and qualitative levels.

CONCLUSIONS

Results provide preliminary evidence supporting the effectiveness of dTMS for SUDs treatment. Current limitations and future directions are critically discussed, highlighting the need for further rigorous research to refine the therapeutic potential and develop consensus-based guidelines for dTMS clinical application.

A roadmap for transformative translational research on gambling disorder in the UK

The UK has one of the highest rates of recreational gambling in the world. Some vulnerable individuals progressively lose control over gambling and develop at-risk gambling or gambling disorder (GD), characterised by the compulsive pursuit of gambling. GD destroys lives and incurs massive costs to societies, yet only a few treatments are available. Failure to develop a wider range of interventions is in part due to a lack of funding that has slowed progress in the translational research necessary to understand the individual vulnerability to switch from controlled to compulsive gambling. Current preclinical models of GD do not operationalise the key clinical features of the human condition. The so-called "gambling tasks" for non-human mammals almost exclusively assess probabilistic decision-making, which is not real-world gambling. While they have provided insights into the psychological and neural mechanisms involved in the processing of gains and losses, these tasks have failed to capture those underlying real-world gambling and its compulsive manifestation in humans. Here, we highlight the strengths and weaknesses of current gambling-like behaviour tasks and suggest how their translational validity may be improved. We then propose a theoretical framework, the incentive habit theory of GD, which may prove useful for the operationalisation of the biobehavioural mechanisms of GD in preclinical models. We conclude with a list of recommendations for the development of next-generation preclinical models of GD and discuss how modern techniques in animal behavioural experimentation can be deployed in the context of GD preclinical research to bolster the translational pipeline.

The neurobiology of overeating

Food intake serves to maintain energy homeostasis; however, overeating can result in obesity, which is associated with serious health complications. In this review, we explore the intricate relationship between overeating, obesity, and the underlying neurobiological mechanisms. We review the homeostatic and hedonic feeding systems, highlighting the role of the hypothalamus and reward systems in controlling food intake and energy balance. Dysregulation in both these systems leads to overeating, as seen in genetic syndromes and environmental models affecting appetite regulation when consuming highly palatable food. The concept of "food addiction" is examined, drawing parallels to drug addiction. We discuss the cellular substrate for addiction-related behavior and current pharmacological obesity treatments-in particular, GLP-1 receptor agonists-showcasing synaptic plasticity in the context of overeating and palatable food exposure. A comprehensive model integrating insights from addiction research is proposed to guide effective interventions for maladaptive feeding behaviors. Ultimately, unraveling the neurobiological basis of overeating holds promise for addressing the pressing public health issue of obesity.

Functional magnetic resonance imaging in prurigo nodularis: A call to study neural sensitization phenomena

Prurigo nodularis is a chronic pruritic, inflammatory skin condition characterized by nodular skin lesions in a typical distribution pattern caused by various dermatologic and/or nondermatologic conditions. In recent years, significant advances have been made in the understanding of the cutaneous pathophysiology of prurigo nodularis, resulting in novel treatment options such as interleukin-4, -13, -17, and -31 or Janus kinase inhibitors. Many aspects of the neurophysiology are largely unknown, including the processing in the central structural and functional network involved in prurigo nodularis. Functional neuroimaging allows noninvasive assessment of brain function and structure. Due to its high spatial resolution and temporal precision, functional magnetic resonance imaging has proven to be a suitable method for exploring neural mechanisms and assessing pharmacologic effects in dermatologic research. In this systematic review, the current knowledge of functional magnetic resonance imaging in the context of prurigo nodularis and its centrally active treatment options is summarized.

Disentangling the effects of self-control and the use of tobacco and cannabis on violence perpetration from childhood to early adulthood

Associations among self-control, substance use (e.g., tobacco and cannabis use), and violence perpetration have been documented during the adolescent years, but the direction of these associations is not well understood. Using five assessments (covering 9 years) from a prospective-longitudinal study, we examined self-control as a precursor and subsequent mechanism of associations between adolescent substance use and physical violence perpetration. Data came from a large, ethnically diverse sample (n = 1,056). Youth reported their self-control at ages 11, 13, 15, 17, and 20; and their tobacco and cannabis use, and physical violence perpetration at ages 13, 15, 17, and 20. Cross-lagged panel analyses examined associations between these constructs over time. More self-control in late childhood and early adolescence was associated with less future tobacco and cannabis use and physical violence perpetration. Tobacco use was partially associated with more physical violence over time; these associations were not mediated by self-control. Tobacco use in early adolescence was associated with future cannabis use; during late adolescence, tobacco and cannabis use were reciprocally associated over time. Cannabis use was not associated with future physical violence perpetration. Early adolescent self-control plays an important role in later substance use and violence perpetration, and tobacco use has unique links with both later cannabis use and violence perpetration. Supporting the capacities for self-control in late childhood and early adolescence and preventing the initiation and use of entry-level substances could play an important role in preventing both substance use and violence perpetration and their many costs to society.

Emerging medications and pharmacological treatment approaches for substance use disorders

Medications to treat substance use disorders (SUDs) remain suboptimal or, in the case of stimulants and cannabis, non-existent. Many factors have contributed to this paucity, including the biological complexity of addiction, regulatory challenges, and a historical lack of enthusiasm among pharmaceutical companies to commit resources to this disease space. Despite these headwinds, the recent opioid crisis has highlighted the devastating consequences of SUDs for both individuals and society, stimulating urgent efforts to identify novel treatment approaches. In addition, several neurobiological systems have been recently implicated in unique aspects of drug reward, opening the door to candidate medications with novel mechanisms of action. Here, we provide an overview of efforts to target several of these new systems, with a focus on those that are the subject of ongoing clinical trials as well as being areas of interest among the authors' research groups (MHJ, MTB, NAE). Specifically, we discuss new classes of medications targeting the serotonin 2A receptor (i.e., psychedelics), glucagon-like peptide 1 receptor, cannabidiol, dynorphin/kappa opioid receptor, orexin/hypocretin, and oxytocin receptor systems, as well as emergent approaches for modulating the more canonical dopaminergic system via agonist therapies for stimulant use disorders. Collectively, innovations in this space give reason for optimism for an improved therapeutic landscape for substance use disorders in the near future.

Cathodal Transcranial Direct Current Stimulation Does Not Change Implicit Associations Against Alcohol in Alcohol Use Disorder: A Preregistered Clinical Trial

Addictive behaviour is shaped by the dynamic interaction of implicit, bottom-up and explicit, top-down cognitive processes. In alcohol use disorder (AUD), implicit alcohol-related associations have been shown to predict increased subsequent alcohol consumption and are linked to the risk of relapse. Explicit cognitive processes, exerting prefrontal top-down control, are particularly significant during the critical period following the decision to abstain. This study aims to map implicit and explicit cognitive processes in recently abstinent individuals with AUD and to explore the effect of cathodal transcranial direct current stimulation (tDCS) on implicit associations by modulating top-down control. In this preregistered, double-blind, sham-controlled clinical trial, 30 abstinent individuals with AUD participated in two experimental sessions. They received either 2 mA cathodal tDCS to the left dorsolateral prefrontal cortex (dlPFC) or sham tDCS in a crossover design. During tDCS, participants completed the alcohol approach implicit association test (IAT) and the drinking identity IAT, along with two control tasks. Additionally, we collected explicit ratings of the IAT stimuli and assessed craving before and after each experimental session. Preregistered ANOVAs revealed significant implicit alcohol-avoidance and non-drinking identity biases. Cathodal tDCS did not modulate IAT scores. Explicit ratings showed a preference for non-alcoholic drinks and non-drinking identity, correlating moderately with IAT scores. Exploratory analyses indicated that cathodal tDCS mitigated the increase in nicotine craving during the experimental session. This preregistered clinical trial provides robust evidence that single-session cathodal tDCS to the left dorsolateral prefrontal cortex does not modulate implicit associations in AUD, with Bayesian analyses corroborating the absence of tDCS effects. Our results emphasize the impact of contextual factors on the interplay between explicit and implicit cognitive processes and underscore the importance of investigating multisession stimulation paradigms in future research.

Delineating anticipatory arousal from reward consumption: evaluating fixed-intervals in cocaine seeking-taking response chains

RATIONALE

Anticipation is a critical antecedent to drug use, in which the prospect of imminent drug availability can potently motivate instrumental actions directed to procure it. Models that capture the behavioral dynamics that precede drug access may allow for the dissociation of key neural mechanisms underlying appetitive or consummatory processes in drug self-administration.

OBJECTIVES

We aimed to isolate measurements attributed to the procurement and consumption of a reward by defining distinct actions for each using a chain-schedule of reinforcement.

METHODS

Male Long-Evans rats were trained to self-administer cocaine or saccharin under a chained schedule of reinforcement (FI-FR) in order to dissociate appetitive ('seeking') from consummatory ('taking') behaviors. Completion of a fixed-interval (5 min) was followed by 5 min of continuously reinforced responding (FR1) on another lever.

RESULTS

The FI-FR chain procedure appears to provide sensitive and dissociable dimensions of cocaine self-administration within a single experimental session. Importantly, we demonstrate that responding during the FI (i.e., seeking) link tracks with the incentive value of anticipated reward access - whereby response rates corresponded to expected reward magnitude, degree of reward-specific satiety, and general motivational state.

CONCLUSIONS

The FI component is a sensitive and reliable index of motivational changes induced by either the extrinsic incentive value of reinforcement (i.e., anticipated dose) or intrinsic motive states (i.e., satiety or deprivation). This procedure provides a valuable tool for interrogating the neural dynamics of drug-seeking and -taking behavior, in isolation.

Prelimbic cortex is involved in the regulation of morphine-induced conditioned place preference in both resistant and sensitive mice

A primary behavioral pathology in drug addiction is the overpowering motivational strength and decreased ability to control the desire to obtain drugs, which shows some variation between different individuals. Here, using a morphine-induced conditioned place preference (CPP) model with footshock, we found that mice exhibited significant individual differences in morphine-induced addiction. Despite the consequences of footshock, a small percentage of mice (24%) still showed stable morphine preference, demonstrating resistant to punishment. The majority of mice (76%) were relatively sensitive to punishment and showed termination of morphine preference. As a region of advanced cognitive function in the mammalian brain, the medial prefrontal cortex (mPFC) is involved in regulating drug-induced addictive behaviors. We found that activating the pyramidal neurons in the prelimbic cortex (PrL) could effectively reverse morphine-induced CPP in resistant mice, and inhibiting pyramidal neurons in the PrL could promote morphine-induced CPP in sensitive mice. To further explore the differences between resistant and sensitive mice, we analyzed the differences in gene expression in their PrL regions through RNA-seq analysis. The results showed that compared to sensitive mice, the significantly downregulated differentially expressed genes (DEGs), such as Panx2, Tcf7l2, Htr2c, Htr5a, Orai3, Slc24a4 and Cacnb2, in resistant mice were mainly involved in synaptic formation and neurodevelopment. We speculated that there may be defects in the neuronal system of resistant mice, and caused they are more prone to morphine-induced CPP. These findings are likely to contribute to research in gene therapy, and they may also serve as potential therapeutic targets for drug addiction.

Human brain organoids for understanding substance use disorders

Substance use disorders (SUDs) are complex mental health conditions involving a problematic pattern of substance use. Challenges remain in understanding its neural mechanisms, which are likely to lead to improved SUD treatments. Human brain organoids, brain-like 3D in vitro cultures derived from human stem cells, show unique potential in recapitulating the response of a developing human brain to substances. Here, we review the recent progress in understanding SUD using human brain organoid models focusing on neurodevelopmental perspectives. We first summarize the background of SUD in humans. Moreover, we introduce the development of various human brain organoid models and then discuss current progress and findings underlying the abuse of substances like nicotine, alcohol, and other addictive drugs using organoid models. Furthermore, we review efforts to develop organ chips and microphysiological systems to engineer better human brain organoids for advancing SUD studies. Lastly, we conclude by elaborating on the current challenges and future directions of SUD studies using human brain organoids.

Memory Reconsolidation Updating in Substance Addiction: Applications, Mechanisms, and Future Prospects for Clinical Therapeutics

Persistent and maladaptive drug-related memories represent a key component in drug addiction. Converging evidence from both preclinical and clinical studies has demonstrated the potential efficacy of the memory reconsolidation updating procedure (MRUP), a non-pharmacological strategy intertwining two distinct memory processes: reconsolidation and extinction-alternatively termed "the memory retrieval-extinction procedure". This procedure presents a promising approach to attenuate, if not erase, entrenched drug memories and prevent relapse. The present review delineates the applications, molecular underpinnings, and operational boundaries of MRUP in the context of various forms of substance dependence. Furthermore, we critically examine the methodological limitations of MRUP, postulating potential refinement to optimize its therapeutic efficacy. In addition, we also look at the potential integration of MRUP and neurostimulation treatments in the domain of substance addiction. Overall, existing studies underscore the significant potential of MRUP, suggesting that interventions predicated on it could herald a promising avenue to enhance clinical outcomes in substance addiction therapy.

The modulation of cholecystokinin receptor 1 in the NAc core input from VTA on METH-induced CPP acquisition

BACKGROUND

Methamphetamine (METH) is a potent psychostimulant that interferes the functionality of various brain regions and nervous connections, leading to addiction. The nucleus accumbens core (NAcC), primarily composed of gamma-aminobutyric acid (GABAergic) neurons, serves as a critical nucleus intimately related to addictive behavior. Previous research has indicated the involvement of cholecystokinin (CCK) receptors in drug addiction, yet the precise function of CCK receptors within the neural circuitry mediating METH-induced addiction remains elusive.

METHODS

METH-induced conditioned place preference (CPP) model was established in mice. In CCK receptor 1 conditional knockout (CCK1Rflox/flox) or CCK receptor 2 conditional knockout (CCK2Rflox/flox) mice, we then utilized the adeno-associated virus (AAV) transfection system to knock out the specific CCK receptor subtype and explore the function of the CCK receptors in the ventral tegmental area (VTA) to NAcC circuit during METH-induced CPP acquisition.

RESULTS

During the acquisition of METH-induced CPP, the expression of CCK1R, but not CCK2R, was upregulated specifically in NAcC. Genetic disruption of either CCK1R in the NAcC effectively hindered METH-induced CPP acquisition and prevented the hyper-excitability of neurons triggered by METH. Furthermore, CCK is released by dopaminergic neurons in the VTA, projecting to the NAcC. Notably, specifically knocking out CCK1R in the VTADA → NAcCGABA circuit blocked the presynaptic release and synaptic plasticity enhancement induced by METH.

CONCLUSIONS

These discoveries highlight the critical effect of CCK1R in the VTADA → NAcCGABA circuit on METH-induced CPP acquisition and provide a more comprehensive understanding of the mechanisms underlying CCK receptors contributing to the METH-induced addictive behavior.

Cocaine-Induced Remodeling of the Rat Brain Peptidome: Quantitative Mass Spectrometry Reveals Anatomically Specific Patterns of Cocaine-Regulated Peptide Changes

Addiction to psychostimulants, including cocaine, causes widespread morbidity and mortality and is a major threat to global public health. Currently, no pharmacotherapies can successfully treat psychostimulant addiction. The neuroactive effects of cocaine and other psychostimulants have been studied extensively with respect to their modulation of monoamine systems (particularly dopamine); effects on neuropeptide systems have received less attention. Here, we employed mass spectrometry (MS) methods to characterize cocaine-induced peptidomic changes in the rat brain. Label-free peptidomic analysis using liquid chromatography coupled with tandem MS (LC-MS/MS) was used to describe the dynamic changes of endogenous peptides in five brain regions (nucleus accumbens, dorsal striatum, prefrontal cortex, amygdala, and hypothalamus) following an acute systemic cocaine challenge. The improved sensitivity and specificity of this method, coupled with quantitative assessment, enabled the identification of 1376 peptides derived from 89 protein precursors. Our data reveal marked, region-specific changes in peptide levels in the brain induced by acute cocaine exposure, with peptides in the cholecystokinin and melanin-concentrating hormone families being significantly affected. These findings offer new insights into the region-specific effects of cocaine and could pave the way for developing new therapies to treat substance use disorders and related psychiatric conditions.

Voluntary and involuntary motor behaviours in the varieties of religious experience

Religion is a widespread feature of human life. Religions typically include both distinctive varieties of experience and also a set of foundational beliefs. An additional, but often overlooked, part of many religions is their expression through specific actions, which we here designate religious motor behaviours. Here we describe these religious motor behaviours and offer a taxonomy based on the conceptual schemes of movement neuroscience and neurology. Thus, religious rituals include both behaviours characterized by decreased motor output (e.g. ritualistic silence) and behaviours characterized by increased motor output (e.g. ritual dances). Neurology often also distinguishes between movements that are experienced as voluntary or involuntary. We show that this same distinction can also apply to religious experiences, since these may be characterized either by a heightened sense of personal control or a sense of being controlled by an external, divine source. We then use these conceptual structures of movement neuroscience to investigate examples from a wide range of religious contexts. We thereby categorize religious motor behaviours into different classes, focusing on specific examples: repetitive ritual actions; motor behaviours where the experience of volition is altered, such as automatisms; and possession-like states. We suggest that a scientific approach to these behaviours should include their predominant phenomenological presentation, the accompanying subjective experience of volition and the underlying neurocognitive mechanisms. This investigation shows rich parallels between religious motor behaviours and motor behaviours observed in neurological disorders, including those that present with functional neurological symptoms. Our approach does not and should not pathologize religious motor behaviours, but rather draws attention to a rich set of non-clinical motor phenomena that highlights important social, cultural and psychological elements of human movement control. Movement neuroscience and religious activity have unexplored overlaps and can usefully learn from each other.

Acting with awareness is positively correlated with dorsal anterior cingulate cortex glutamate concentration but both are impaired in Internet gaming disorder

Internet gaming disorder (IGD) is increasingly recognized as a public concern for its adverse impacts on cognition and mental health. In IGD, the transition from goal-directed actions to habitual and eventually compulsive behaviors is accompanied by altered neural response within the dorsal anterior cingulate cortex (dACC), a critical region involved in conscious actions. However, the neurochemical profile of the dACC in IGD and its relationship with behavioral awareness remain poorly understood. In this study, 1H-magnetic resonance spectroscopy was employed to quantify dACC glutamate concentration and examine its association with the capacity for 'acting with awareness' among 21 participants with IGD and 19 recreational game users. Results indicated that dACC glutamate levels and behavioral awareness were significantly lower in the IGD group compared to recreational game users. Moreover, a significant positive correlation between awareness and dACC glutamate concentration emerged in the recreational game users' group, a relationship attenuated in those with IGD. In an independent cohort of 107 participants, the positive association between awareness and dACC glutamate concentration was replicated. These findings suggest that reduced dACC glutamate in IGD may underlie diminished awareness of maladaptive habitual behaviors. Enhancing dACC neural excitability through neuromodulation or mindfulness training could represent a potential intervention to restore behavioral awareness.

The effect of individual differences on Pavlovian conditioning in specific Internet-use disorders

The I-PACE model suggests that Internet-use disorders result from the interplay of individual vulnerabilities and cognitive and affective processes. As in substance use disorders, Pavlovian conditioning processes are attributed a key role. However, and despite progress in identifying individual vulnerabilities, factors influencing appetitive conditioning remain poorly understood. We therefore conducted a Pavlovian conditioning experiment in which individuals with risky as well as non-problematic use of either gaming or buying-shopping applications learned to associate different abstract stimuli with either gaming or buying-shopping. Regression analyses were used to identify individual characteristics influencing awareness of the experimental contingencies, speed of acquisition of awareness and the magnitude of the conditioned emotional responses regarding pleasantness and arousal ratings of the stimuli. Results demonstrated successful Pavlovian conditioning and an attentional bias towards reward-predicting cues. Awareness of the experimental contingencies was linked solely to cognitive abilities, while the speed of acquisition of awareness and the magnitude of conditioned responses was influenced by specific personality characteristics, experiences of compensation from using the application and severity of problematic use. Importantly, certain characteristics specifically predicted the magnitude of the conditioned response towards gaming, while others specifically predicted the response towards buying-shopping, highlighting differing vulnerabilities. These findings underscore the importance of targeted interventions and prevention strategies tailored to these specific vulnerability factors. Further implications and limitations are discussed.

Neuronal encoding of behaviors and instrumental learning in the dorsal striatum

The dorsal striatum is instrumental in regulating motor control and goal-directed behaviors. The classical description of the two output pathways of the dorsal striatum highlights their antagonistic control over actions. However, recent experimental evidence implicates both pathways and their coordinated activities during actions. In this review, we examine the different models proposed for striatal encoding of actions during self-paced behaviors and how they can account for evidence harvested during goal-directed behaviors. We also discuss how the activation of striatal ensembles can be reshaped and reorganized to support the formation of instrumental learning and behavioral flexibility. Future work integrating these considerations may resolve controversies regarding the control of actions by striatal networks.

The Incentive-Sensitization Theory of Addiction 30 Years On

The incentive-sensitization theory (IST) of addiction was first published in 1993, proposing that (a) brain mesolimbic dopamine systems mediate incentive motivation ("wanting") for addictive drugs and other rewards, but not their hedonic impact (liking) when consumed; and (b) some individuals are vulnerable to drug-induced long-lasting sensitization of mesolimbic systems, which selectively amplifies their "wanting" for drugs without increasing their liking of the same drugs. Here we describe the origins of IST and evaluate its status 30 years on. We compare IST to other theories of addiction, including opponent-process theories, habit theories of addiction, and prefrontal cortical dysfunction theories of impaired impulse control. We also address critiques of IST that have been raised over the years, such as whether craving is important in addiction and whether addiction can ever be characterized as compulsive. Finally, we discuss several contemporary phenomena, including the potential role of incentive sensitization in behavioral addictions, the emergence of addiction-like dopamine dysregulation syndrome in medicated Parkinson's patients, the role of attentional capture and approach tendencies, and the role of uncertainty in incentive motivation.

Mechanisms of nucleus accumbens deep brain stimulation in treating mental disorders

Growing evidence supports the effectiveness of deep brain stimulation (DBS) in treating various psychiatric disorders. DBS has the potential to selectively stimulate specific subcortical brain areas thus providing high-frequency electric stimulation of these regions. The nucleus accumbens (NAc), a frequent DBS target, has shown promise in treating psychiatric conditions like depression, obsessive-compulsive disorder, and addiction. In this review, we provide an overview across studies investigating the effects of NAc DBS in humans and animals and discuss potential mechanisms underlying its clinical efficacy. We address the anatomical properties of NAc and discuss, in particular, the frequently reported differential effects of NAc shell and NAc core DBS. Moreover, by outlining the various NAc cell types, transmitter systems (i.e., predominantly GABAergic and dopaminergic systems) and anatomical pathways that have been shown to be relevant for NAc DBS stimulation effects, we aim to further elucidate the neurobiological determinants of NAc DBS efficacy. Finally, since treatment effects of NAc DBS are most probably also related to alterations in NAc connected circuits or networks, we review studies focusing on the investigation of NAc DBS network effects. By examining these various components that are assumed to be of relevance in the context of NAc DBS, this review will hopefully contribute to increasing our knowledge about the mechanisms underlying NAc DBS and optimizing future selection of optimal DBS targets.

Disrupting heroin-associated memory reconsolidation through actin polymerization inhibition in the nucleus accumbens core

BACKGROUND

Understanding drug addiction as a disorder of maladaptive learning, where drug-associated or environmental cues trigger drug cravings and seeking, is crucial for developing effective treatments. Actin polymerization, a biochemical process, plays a crucial role in drug-related memory formation, particularly evident in conditioned place preference paradigms involving drugs like morphine and methamphetamine. However, the role of actin polymerization in the reconsolidation of heroin-associated memories remains understudied.

METHODS

This study employed a rodent model of self-administered heroin to investigate the involvement of actin polymerization in the reconsolidation of heroin-associated memories. Rats underwent ten days of intravenous heroin self-administration paired with conditioned cues. Subsequently, a 10-day extinction phase aimed to reduce heroin-seeking behaviors. Following this, rats participated in a 15-minute retrieval trial with or without cues. Immediately post-retrieval, rats received bilateral injections of the actin polymerization inhibitor Latrunculin A (Lat A) into the nucleus accumbens core (NACc), a critical brain region for memory reconsolidation.

RESULTS

Immediate administration of Lat A into the NACc post-retrieval significantly reduced cue-induced and heroin-primed reinstatement of heroin-seeking behavior for at least 28 days. However, administering Lat A 6-hour post-retrieval or without a retrieval trial, as well as administering Jasplakionlide prior to memory reactivation did not affect heroin-seeking behaviors.

CONCLUSIONS

Inhibiting actin polymerization during the reconsolidation window disrupts heroin-associated memory reconsolidation, leading to decreased heroin-seeking behavior and prevention of relapse. These effects are contingent upon the presence of a retrieval trial and exhibit temporal specificity, shedding light on addiction mechanisms and potential therapeutic interventions.

Neural signatures of opioid-induced risk-taking behavior in the prelimbic prefrontal cortex

Opioid use disorder occurs alongside impaired risk-related decision-making, but the underlying neural correlates are unclear. We developed an approach-avoidance conflict task using a modified conditioned place preference procedure to study neural signals of risky opioid seeking in the prefrontal cortex, a region implicated in executive decision-making. Following morphine conditioned place preference, rats underwent a conflict test in which fear-inducing cat odor was introduced in the previously drug-paired side of the apparatus. While the saline-exposed control group avoided cat odor, the morphine group included two subsets of rats that either maintained a preference for the paired side despite the presence of cat odor (Risk-Takers) or exhibited increased avoidance (Risk-Avoiders), as revealed by K-means clustering. Single-unit recordings from the prelimbic cortex (PL) demonstrated decreased neuronal activity upon acute morphine exposure in both Risk-Takers and Risk-Avoiders, but this firing rate suppression was absent after repeated morphine administration. Risk-Avoiders also displayed distinct post-morphine excitation in PL which persisted across conditioning. During the preference test, subpopulations of PL neurons in all groups were either excited or inhibited when rats entered the paired side. Interestingly, the inhibition in PL activity was lost during the subsequent conflict test in both saline and Risk-Avoider groups, but persisted in Risk-Takers. Additionally, Risk-Takers showed an increase in the proportion of PL neurons displaying location-specific firing in the drug-paired side from the preference to the conflict test. Together, our results suggest that persistent PL inhibitory signaling in the drug-associated context during motivational conflict may underlie increased risk-taking behavior following opioid exposure.

Dynamic responses of striatal cholinergic interneurons control behavioral flexibility

Striatal cholinergic interneurons (CINs) are key to regulating behavioral flexibility, involving both extinguishing learned actions and adopting new ones. However, the mechanisms driving these processes remain elusive. In this study, we initially demonstrate that chronic alcohol consumption disrupts the burst-pause dynamics of CINs and impairs behavioral flexibility. We next aimed to elucidate the mechanisms by which CIN dynamics control behavioral flexibility. We found that extinction learning enhances acetylcholine (ACh) release and that mimicking this enhancement through optogenetic induction of CIN burst firing accelerates the extinction process. In addition, we demonstrate that disrupting CIN pauses via continuous optogenetic stimulation reversibly impairs the updating of goal-directed behaviors. Overall, we demonstrate that CIN burst firing, which increases ACh release, promotes extinction learning, aiding the extinguishment of learned behaviors. Conversely, CIN firing pauses, which lead to ACh dips, are crucial for reversal learning, facilitating the adaptation of new actions. These findings shed light on how CIN dynamics regulate behavioral flexibility.

Subjective Assessment of Rdoc-Related Constructs in Addiction and Compulsive Disorders: A Scoping Review

Objective

Obsessive-compulsive and related disorders (OCRDs) and disorders due to addictive behavior (DABs) are prevalent conditions that share common neurobiological and behavioral characteristics. This scoping review aims to identify and map the range of subjective assessment tools (e.g., interviews and self-report instruments) for assessing Research Domain Criteria (RDoC) and related constructs underlying DABs and OCRDs, such as impaired response inhibition, habit formation, and compulsivity.

Method

A scoping review was performed following the PRISMA Extension for Scoping Reviews (PRISMA ScR). The search was conducted in Medline, Web of Science, PsycINFO, and EMBASE databases. No constraints of data or document type were adopted.

Results

The search yielded 615 instruments, of which 79 were deemed transdiagnostic and capable of assessing at least one of the target constructs. Noteworthy tools included are the Cambridge-Chicago Compulsivity Trait Scale, the Self-report Habit Index, the Reward Probability Index, the Threat-Related Reassurance-Seeking Scale, and the recent Positive Valence Systems Scale.

Conclusions

Despite the growing body of literature on OCRDs and DABs as new diagnostic chapters and the number of tools with the potential to assess their transdiagnostic constructs clinically, most instruments were designed to capture dimensions or psychopathology not directly (or primarily) related to OCRDs, DABs and the concepts of impaired response inhibition, habit formation, and compulsivity in the context of these conditions. Further studies exploring the correlation between subjective assessments, corresponding behavior paradigms, and neuroimaging data would be of great value in the translation of RDoC constructs and domains into clinical settings.

Distinct populations suppress or escalate intake of cocaine paired with aversive quinine

BACKGROUND

Only a subset of individuals who encounter illicit drugs become persons with a substance use disorder. Individual differences in aversive reactions to drug-associated phenomena like smoke inhalation and unpleasant taste are predictors for continued use. While several preclinical studies have explored self-administration involving aversive cues, none have simultaneously introduced aversion with the initial drug self-administration. We aimed to develop such a model by pairing intravenous cocaine with intraoral quinine self-administration from the outset and investigate whether repeated exposure to an aversive stimulus would alter its hedonic value under laboratory conditions.

METHODS

Twenty-seven male and female Sprague Dawley rats self-administered intravenous/intraoral (cocaine/quinine) for 2h/day over 14 days. This was followed by a 1-day quinine-only extinction session, a 3-day return to self-administration, and an intraoral infusion session to assess quinine taste reactivity (TR).

RESULTS

We identified three distinct groups. The first self-administered very little cocaine, while the second sharply escalated cocaine intake. Both groups had similar aversive TR to quinine, suggesting that the escalating group did not habituate to the aversive cue but pursued drug despite it. We also identified a third group with high initial intake that decreased over time. This decrease predicted high aversive TR, and we argue this group may represent individuals who engage in excessive use on their first encounter and subsequently find self-administration to be aversive.

CONCLUSIONS

Our novel model yields three distinct groups that differ in self-administration patterns and aversive cue valuation.

Within-episode relations among simultaneous alcohol and cannabis use and continued drinking: The role of momentary subjective responses, craving, and drinking context

BACKGROUND

Simultaneous alcohol and cannabis use is associated with riskier daily drinking. However, little research has tested momentary mechanisms through which simultaneous use predicts continued drinking during acute drinking episodes. The current study tested whether simultaneous use moments predicted within-episode increases in subjective responses, craving, and continued drinking, and whether these relations were potentiated in social versus solitary settings.

METHODS

Emerging adults who co-use alcohol and cannabis (N = 85) completed 21 days of ecological momentary assessment with event-contingent reports during drinking episodes. Three-level multilevel models tested whether simultaneous (vs. alcohol-only) use moments indirectly predicted subsequent, continued drinking through subjective responses (i.e., high-arousal positive/stimulant, high-arousal negative/aggression, low-arousal positive/relaxation, low-arousal negative/impairment) and alcohol craving, and whether relations differed by social versus solitary contexts.

RESULTS

Within drinking episodes, simultaneous (vs. alcohol-only) use moments were associated with increased stimulation, which was indirectly associated with continued drinking through increased alcohol craving. Additionally, the relation between simultaneous (vs. alcohol-only) use and stimulating effects was potentiated during solitary drinking moments, whereas the relation between stimulating effects and craving was potentiated during social drinking moments. However, stimulating effects were higher in social contexts across all moments. Finally, simultaneous (vs. alcohol-only) use moments were associated with increased relaxation, which was indirectly associated with a lower likelihood of continued drinking through lesser craving.

CONCLUSIONS

Simultaneous use predicted both continued within-episode drinking and cessation of drinking, with acute subjective effects and craving as mechanisms, dependent upon context. Just-in-time interventions should consider targeting affect, craving, and context in event-specific interventions.

KETAMINE: Neural- and network-level changes

Ketamine is a widely used clinical drug that has several functional and clinical applications, including its use as an anaesthetic, analgesic, anti-depressive, anti-suicidal agent, among others. Among its diverse behavioral effects, it influences short-term memory and induces psychedelic effects. At the neural level across different brain areas, it modulates neural firing rates, neural tuning, brain oscillations, and modularity, while promoting hypersynchrony and random connectivity between neurons. In our recent studies we demonstrated that topical application of ketamine on the visual cortex alters neural tuning and promotes vigorous connectivity between neurons by decreasing their firing variability. Here, we begin with a brief review of the literature, followed by results from our lab, where we synthesize a dendritic model of neural tuning and network changes following ketamine application. This model has potential implications for focused modulation of cortical networks in clinical settings. Finally, we identify current gaps in research and suggest directions for future studies, particularly emphasizing the need for more animal experiments to establish a platform for effective translation and synergistic therapies combining ketamine with other protocols such as training and adaptation. In summary, investigating ketamine's broader systemic effects, not only provides deeper insight into cognitive functions and consciousness but also paves the way to advance therapies for neuropsychiatric disorders.

G protein-coupled receptor modulation of striatal dopamine transmission: Implications for psychoactive drug effects

Dopamine transmission in the striatum is a critical mediator of the rewarding and reinforcing effects of commonly misused psychoactive drugs. G protein-coupled receptors (GPCRs) that bind a variety of neuromodulators including dopamine, endocannabinoids, acetylcholine and endogenous opioid peptides regulate dopamine release by acting on several components of dopaminergic circuitry. Striatal dopamine release can be driven by both somatic action potential firing and local mechanisms that depend on acetylcholine released from striatal cholinergic interneurons. GPCRs that primarily regulate somatic firing of dopamine neurons via direct effects or modulation of synaptic inputs are likely to affect distinct aspects of behaviour and psychoactive drug actions compared with those GPCRs that primarily regulate local acetylcholine-dependent dopamine release in striatal regions. This review will highlight mechanisms by which GPCRs modulate dopaminergic transmission and the relevance of these findings to psychoactive drug effects on physiology and behaviour.

The Neurocircuitry of Substance Use Disorder, Treatment, and Change: A Resource for Clinical Psychiatrists

Substance use disorder (SUD) is common in psychiatric patients and has a negative impact on health and well-being. However, SUD often goes untreated, and there is a need for psychiatrists, of all specialties, to address this pervasive clinical problem. In this review, the authors' goal is to provide a resource that describes treatments for SUD, using neuroscience as a framework. They discuss the effect of pharmacotherapy on craving, intoxication, and withdrawal and its ability to interrupt the cycle of substance use in SUD. The neuroscience of stress is reviewed, including medications targeting neurotransmitter systems activated by alarm and fear. Neuroplasticity and promising treatments that use this mechanism, including ketamine, psilocybin, and transcranial magnetic stimulation (TMS), are discussed. The authors conclude by listing resources and practice guidelines for physicians interested in learning more about treatments for SUD.

Conditional deletion of the AMPA-GluA1 and NMDA-GluN1 receptor subunit genes in midbrain D1 neurons does not alter cocaine reward in mice

Synaptic plasticity in the mesolimbic dopamine (DA) system contributes to the neural adaptations underlying addictive behaviors and relapse. However, the specific behavioral relevance of glutamatergic excitatory drive onto dopamine D1 receptor (D1R)-expressing neurons in mediating the reinforcing effect of cocaine remains unclear. Here, we investigated how midbrain AMPAR and NMDAR function modulate cocaine reward-related behavior using mutant mouse lines lacking the glutamate receptor genes Gria1 or Grin1 in D1R-expressing neurons (GluA1D1CreERT2 or GluN1D1CreERT2, respectively). We found that conditional genetic deletion of either GluA1 or GluN1 within this neuronal sub-population did not impact the ability of acute cocaine injection to increase intracranial self-stimulation (ICSS) ratio or reduced brain reward threshold compared to littermate controls. Additionally, our data demonstrate that deletion of GluA1 and GluN1 receptor subunits within D1R-expressing neurons did not affect cocaine reinforcement in an operant self-administration paradigm, as mutant mice showed comparable cocaine responses and intake to controls. Given the pivotal role of glutamate receptors in mediating relapse behavior, we further explored the impact of genetic deletion of AMPAR and NMDAR onto D1R-expressing neurons on cue-induced reinstatement following extinction. Surprisingly, deletion of AMPAR and NMDAR onto these neurons did not impair cue-induced reinstatement of cocaine-seeking behavior. These findings suggest that glutamatergic activity via NMDAR and AMPAR in D1R-expressing neurons may not exclusively mediate the reinforcing effects of cocaine and cue-induced reinstatement.

Resveratrol by elevating the SIRT1 BDNF, GDNF and PSD95 levels reduce heroin addiction related behaviors

OBJECTIVE

To study the effects of resveratrol on heroin addiction-related behaviors and to preliminarily explore the possible intervention mechanism of resveratrol in heroin dependence.

METHODS

The effects of resveratrol on heroin withdrawal symptoms were observed by naloxone; The effect of resveratrol on heroin reward memory acquisition was detected by CPP paradigm; The effect of resveratrol on the mental excitability of heroin was tested by open field experiment; The effect of resveratrol on heroin spatial learning and memory was tested by water maze test. Western blot was used to detect Sirtuin 1 (SIRT1) Expression of brain-derived neurotrophic factor (BDNF), glial cell derived neurotrophic factor (GDNF), and postsynaptic density protein (PSD95).

RESULTS

The behavioral results showed that the withdrawal behavior of the resveratrol intervention group was reduced compared with the heroin chronic dependence group (P<0.05), and the shift score of the conditioned place preference test of the resveratrol intervention group was reduced compared with the heroin chronic dependence group (P<0.05) The spatial learning and memory ability of the water maze in the resveratrol intervention group was improved compared with the heroin chronic dependence group (P<0.05), and the mental excitability of the resveratrol intervention group was lower than that of the heroin chronic dependence group (P<0.05), but higher than that of the saline group (P<0.05); SIRT1 The expression levels of BDNF, GDNF and PSD95 protein were significantly increased (P<0.05).

CONCLUSION

The behavioral results of this study suggest that resveratrol can be used as a potential drug to treat heroin dependence. At the same time, SIRT1 The expression of BDNF, GDNF, and PSD95 increased; SIRT1, BDNF, GDNF, and PSD95 play an essential role in heroin addiction.

Frustrative Nonreward: Behavior, Circuits, Neurochemistry, and Disorders

The surprising omission or reduction of vital resources (food, fluid, social partners) can induce an aversive emotion known as frustrative nonreward (FNR), which can influence subsequent behavior and physiology. FNR is an integral mediator of irritability/aggression, motivation (substance use disorders, depression), anxiety/fear/threat, learning/conditioning, and social behavior. Despite substantial progress in the study of FNR during the twentieth century, research lagged in the later part of the century and into the early twenty-first century until the National Institute of Mental Health's Research Domain Criteria initiative included FNR and loss as components of the negative valence domain. This led to a renaissance of new research and paradigms relevant to basic and clinical science alike. The COVID-19 pandemic's extensive individual and social restrictions were correlated with increased drug and alcohol use, social conflict, irritability, and suicide, all potential consequences of FNR. This article highlights animal models related to these psychiatric disorders and symptoms and presents recent advances in identifying the brain regions and neurotransmitters implicated.

Enhancing translation: A need to leverage complex preclinical models of addictive drugs to accelerate substance use treatment options

Preclinical models of addictive drugs have been developed for decades to model aspects of the clinical experience in substance use disorders (SUDs). These include passive exposure as well as volitional intake models across addictive drugs and have been utilized to also measure withdrawal symptomatology and potential neurobehavioral mechanisms underlying relapse to drug seeking or taking. There are a number of Food and Drug Administration (FDA)-approved medications for SUDs, however, many demonstrate low clinical efficacy as well as potential sex differences, and we also note gaps in the continuum of care for certain aspects of clinical experiences in individuals who use drugs. In this review, we provide a comprehensive update on both frequently utilized and novel behavioral models of addiction with a focus on translational value to the clinical experience and highlight the need for preclinical research to follow epidemiological trends in drug use patterns to stay abreast of clinical treatment needs. We then note areas in which models could be improved to enhance the medications development pipeline through efforts to enhance translation of preclinical models. Next, we describe neuroscience efforts that can be leveraged to identify novel biological mechanisms to enhance medications development efforts for SUDs, focusing specifically on advances in brain transcriptomics approaches that can provide comprehensive screening and identification of novel targets. Together, the confluence of this review demonstrates the need for careful selection of behavioral models and methodological parameters that better approximate the clinical experience combined with cutting edge neuroscience techniques to advance the medications development pipeline for SUDs.

Traumatic Brain Injury Exacerbates Alcohol Consumption and Neuroinflammation with Decline in Cognition and Cholinergic Activity

Traumatic brain injury (TBI) is a global health challenge, responsible for 30% of injury-related deaths and significantly contributing to disability. Annually, over 50 million TBIs occur worldwide, with most adult patients at emergency departments showing alcohol in their system. TBI is also a known risk factor for alcohol abuse, yet its interaction with alcohol consumption remains poorly understood. In this study, we demonstrate that the fluid percussion injury (FPI) model of TBI in mice significantly increases alcohol consumption and impairs cognitive function. At cellular levels, FPI markedly reduced the number and activity of striatal cholinergic interneurons (CINs) while increasing microglial cells. Notably, depleting microglial cells provided neuroprotection, mitigating cholinergic loss and enhancing cholinergic activity. These findings suggest that TBI may promote alcohol consumption and impair cognitive abilities through microglia activation and consequently reduced cholinergic function. Our research provides critical insights into the mechanisms linking TBI with increased alcohol use and cognitive deficits, potentially guiding future therapeutic strategies.

Atypical effective connectivity from the frontal cortex to striatum in alcohol use disorder

Alcohol use disorder (AUD) is a profound psychiatric condition marked by disrupted connectivity among distributed brain regions, indicating impaired functional integration. Previous connectome studies utilizing functional magnetic resonance imaging (fMRI) have predominantly focused on undirected functional connectivity, while the specific alterations in directed effective connectivity (EC) associated with AUD remain unclear. To address this issue, this study utilized multivariate pattern analysis (MVPA) and spectral dynamic causal modeling (DCM). We recruited 32 abstinent men with AUD and 30 healthy controls (HCs) men, and collected their resting-state fMRI data. A regional homogeneity (ReHo)-based MVPA method was employed to classify AUD and HC groups, as well as predict the severity of addiction in AUD individuals. The most informative brain regions identified by the MVPA were further investigated using spectral DCM. Our results indicated that the ReHo-based support vector classification (SVC) exhibits the highest accuracy in distinguishing individuals with AUD from HCs (classification accuracy: 98.57%). Additionally, our results demonstrated that ReHo-based support vector regression (SVR) could be utilized to predict the addiction severity (alcohol use disorders identification test, AUDIT, R2 = 0.38; Michigan alcoholism screening test, MAST, R2 = 0.29) of patients with AUD. The most informative brain regions for the prediction include left pre-SMA, right dACC, right LOFC, right putamen, and right NACC. These findings were validated in an independent data set (35 patients with AUD and 36 HCs, Classification accuracy: 91.67%; AUDIT, R2 = 0.17; MAST, R2 = 0.20). The results of spectral DCM analysis indicated that individuals with AUD exhibited decreased EC from the left pre-SMA to the right putamen, from the right dACC to the right putamen, and from the right LOFC to the right NACC compared to HCs. Moreover, the EC strength from the right NACC to left pre-SMA and from the right dACC to right putamen mediated the relationship between addiction severity (MAST scores) and behavioral measures (impulsive and compulsive scores). These findings provide crucial evidence for the underlying mechanism of impaired self-control, risk assessment, and impulsive and compulsive alcohol consumption in individuals with AUD, providing novel causal insights into both diagnosis and treatment.

Associations of Reversal Learning Performance With Personality Disorder Profile and Drug Abuse History in a Sample of Prison Inmates

Prison inmate samples present a high prevalence of impulsivity- and compulsivity-related behavioral problems. The Probabilistic Reversal Learning Task (PRLT) is a useful tool to assess decision-making, and we explore its associations with inmates' personality disorder (antisocial personality disorder, APD; obsessive-compulsive personality disorder, OCPD; or both) and history of drug abuse. Mixed-effects methods were used to model acquisition and reacquisition curves across PRLT, in a sample of 275 prison inmates diagnosed with OCPD, APD, or both. Two aspects were assessed: general discrimination learning and decision-making inflexibility. Participants with a mixed personality disorder profile showed a clear pattern of decisional inflexibility. A history of drug abuse was associated with a general poorer performance but not with decision-making inflexibility. Inability to adapt to changing contingencies, and thus to adverse consequences of previously rewarded choices, was not linked to compulsivity, as hypothesized to be present in OCPD and substance use disorders, but to the mixed APD/OCPD profile.

Cross-species brain-wide mapping reveals a conserved and coordinated network engaged by NAc DBS

Nucleus accumbens (NAc) deep brain stimulation (DBS) has been increasingly explored as a treatment modality for refractory neuropsychiatric disorders. Uncovering the accumbens network that is engaged by DBS is a critical step forward in understanding how modulating this important node impacts the broader mesocorticolimbic circuit. Using whole-brain clearing and unbiased, brain-wide neural activity mapping, we found that NAc DBS increases neural activity in a coordinated mesocorticolimbic network in mice. Simultaneous intracranial electrophysiology recordings from the human NAc and brief stimulation epochs of homologous mesocorticolimbic nodes revealed similar connectivity. Altogether, these results identify specific connectivity conserved across species within the mesocorticolimbic circuit that may underlie mechanisms of NAc DBS.

Understanding the shift to compulsion in addiction: insights from personality traits, social factors, and neurobiology

Compulsion stands as a central symptom of drug addiction; however, only a small fraction of individuals who use drugs exhibit compulsive characteristics. Differences observed in Sign-trackers (ST) and Goal-trackers (GT) during Pavlovian conditioning may shed light on individual variances in drug addiction. Here, we focus on the behavioral attributes, formation processes, and neural mechanisms underlying ST and how they drive addiction toward compulsivity in humans. We will explore addiction from three interconnected levels: individual personality traits, social factors, and neurobiology. Furthermore, we distinguish between the processes of sensitization and habituation within ST. These nuanced distinctions across various aspects of addiction will contribute to our understanding of the addiction development process and the formulation of targeted preventive strategies.

Decreased consumption of natural rewards in rhesus monkeys with prolonged methamphetamine abstinence

Rationale

Relapse to drug use is a major clinical challenge in the treatment of addictive disorders, including psychostimulant use and may be exacerbated by reduced sensitivity to natural, non-drug reward. Given the relatively limited set of outcomes, and short withdrawal time in rodent studies, we conducted a more detailed assessment of the response to natural rewards in methamphetamine (METH) naive versus exposed monkeys during long-term abstinence.

Methods

This study introduced an improved sucrose preference test (iSPT) to assess natural reward seeking and consumption in monkeys with long-term abstinence after methamphetamine (METH) use. The test was administered to sixteen naive monkeys and five METH exposed monkeys that had been abstinent for at least 3 months.

Results

METH exposed monkeys showed a lower sucrose preference score in both the iSPT (z = -2.10, p = 0.036) and the sucrose preference test (z = -2.61, p = 0.009). The sucrose preference score was significantly correlated with the latency of the establishment of stable sucrose-preference (r = -0.76, df = 46, p < 0.001) but not with the other variables. Furthermore, water-sucrose switch latency and switch times were significantly negatively correlated (r = -0.50, df = 20, p = 0.02).

Conclusion

These results show reductions in natural reward consumption during long-term methamphetamine abstinence.

Sex-specific differences in brain activity dynamics of youth with a family history of substance use disorder

An individual's risk of substance use disorder (SUD) is shaped by a complex interplay of potent biosocial factors. Current neurodevelopmental models posit vulnerability to SUD in youth is due to an overreactive reward system and reduced inhibitory control. Having a family history of SUD is a particularly strong risk factor, yet few studies have explored its impact on brain function and structure prior to substance exposure. Herein, we utilized a network control theory approach to quantify sex-specific differences in brain activity dynamics in youth with and without a family history of SUD, drawn from a large cohort of substance-naïve youth from the Adolescent Brain Cognitive Development Study. We summarize brain dynamics by calculating transition energy, which probes the ease with which a whole brain, region or network drives the brain towards a specific spatial pattern of activation (i.e., brain state). Our findings reveal that a family history of SUD is associated with alterations in the brain's dynamics wherein: i) independent of sex, certain regions' transition energies are higher in those with a family history of SUD and ii) there exist sex-specific differences in SUD family history groups at multiple levels of transition energy (global, network, and regional). Family history-by-sex effects reveal that energetic demand is increased in females with a family history of SUD and decreased in males with a family history of SUD, compared to their same-sex counterparts with no SUD family history. Specifically, we localize these effects to higher energetic demands of the default mode network in females with a family history of SUD and lower energetic demands of attention networks in males with a family history of SUD. These results suggest a family history of SUD may increase reward saliency in males and decrease efficiency of top-down inhibitory control in females. This work could be used to inform personalized intervention strategies that may target differing cognitive mechanisms that predispose individuals to the development of SUD.

Emerging drugs in phase II and III clinical development for the treatment of alcohol use disorder

INTRODUCTION

Alcohol Use Disorder (AUD) poses an ongoing significant global health burden. AUD is highly prevalent and affects not only the individuals with AUD, but also their communities and society at large. Even though pharmacotherapy is an integral part of AUD treatment, the few available substances show limited efficacy and limited clinical impact. Thus, there is a need for new innovative pharmacotherapeutic approaches.

AREAS COVERED

This paper provides a comprehensive review of drugs approved for the treatment of AUD as well as those currently in phase II and III development. Data from recent clinical trials has been reviewed and supplemented by additional literature based on a systematic search of the PubMed database and clinical trials registries. Compounds discussed include disulfiram, naltrexone, nalmefene, acamprosat, baclofen, sodium oxybate, doxazosin, varenicline, zonisamide, gabapentin, apremilast, ibudilast, ivermectin, tolcapone, mifepristone, suvorexant, ketamine, psilocybin, semaglutide, oxytocin and cannabidiol.

EXPERT OPINION

Even though the majority of the discussed compounds lack sufficient evidence to support their efficacy, multiple promising new treatment options are currently under investigation. Future research has to consider specific phenotypes and subgroups of AUD as well as a possible enhancement of the effects of psychotherapy through combination with pharmacotherapy. Practitioners should be encouraged to use available compounds to support existing therapeutic regimens.

Optogenetic inhibition of light-captured alcohol-taking striatal engrams facilitates extinction and suppresses reinstatement

BACKGROUND

Alcohol use disorder (AUD) is a complex condition, and it remains unclear which specific neuronal substrates mediate alcohol-seeking and -taking behaviors. Engram cells and their related ensembles, which encode learning and memory, may play a role in this process. We aimed to assess the precise neural substrates underlying alcohol-seeking and -taking behaviors and determine how they may affect one another.

METHODS

Using FLiCRE (Fast Light and Calcium-Regulated Expression; a newly developed technique which permits the trapping of acutely activated neuronal ensembles) and operant self-administration (OSA), we tagged striatal neurons activated during alcohol-taking behaviors. We used FLiCRE to express an inhibitory halorhodopsin in alcohol-taking neurons, permitting loss-of-function manipulations.

RESULTS

We found that the inhibition of OSA-tagged alcohol-taking neurons decreased both alcohol-seeking and -taking behaviors in future OSA trials. In addition, optogenetic inhibition of these OSA-tagged alcohol-taking neurons during extinction training facilitated the extinction of alcohol-seeking behaviors. Furthermore, inhibition of these OSA-tagged alcohol-taking neurons suppressed the reinstatement of alcohol-seeking behaviors, but, interestingly, it did not significantly suppress alcohol-taking behaviors during reinstatement.

CONCLUSIONS

Our findings suggest that alcohol-taking neurons are crucial for future alcohol-seeking behaviors during extinction and reinstatement. These results may help in the development of new therapeutic approaches to enhance extinction and suppress relapse in individuals with AUD.

Alcohol consumption does not impact delta and kappa opioid receptor-mediated synaptic depression in dorsolateral striatum of adult male mice

Many drugs of abuse, including alcohol, disrupt long-term synaptic depression (LTD) at dorsal striatal glutamate synapses. This disruption is common to many forms of LTD that are mediated by G protein coupled receptors (GPCRs) that signal through the inhibitory Gi/o class of G proteins. A loss of LTD is thought to mediate behavioral changes associated with the development of substance use disorders. We have previously shown in multiple studies that LTD mediated by the Gi/o-coupled mu opioid receptor is disrupted by in vivo opioid and alcohol exposure in adolescent and adult mice. One of our previous studies suggested that LTD mediated by delta and kappa opioid receptors was resistant to the LTD-disrupting properties of in vivo opioid exposure. We hypothesized that delta and kappa opioid receptor-mediated LTD would be exceptions to the generalizable observation that forms of dorsal striatal Gi/o-coupled receptor LTD are disrupted by drugs of abuse. Specifically, we predicted that these forms of LTD would be resistant to the deleterious effects of alcohol consumption, just as they were resistant to opioid exposure. Indeed, in adult male mice that drank alcohol for 3 weeks, delta and kappa opioid receptor-mediated LTD at glutamatergic inputs to direct pathway and indirect pathway medium spiny neurons in the dorsolateral striatum was unaffected by alcohol. These data demonstrate that alcohol effects on GPCR-mediated LTD are not generalizable across all types of Gi/o-coupled GPCRs.

GABA system in the prefrontal cortex involved in psychostimulant addiction

Drug addiction is a chronic and relapse brain disorder. Psychostimulants such as cocaine and amphetamine are highly addictive drugs. Abuse drugs target various brain areas in the nervous system. Recent studies have shown that the prefrontal cortex (PFC) plays a key role in regulating addictive behaviors. The PFC is made up of excitatory glutamatergic cells and gamma-aminobutyric acid (GABAergic) interneurons. Recently, studies showed that GABA level was related with psychostimulant addiction. In this review, we will introduce the role and mechanism of GABA and γ-aminobutyric acid receptors (GABARs) of the PFC in regulating drug addiction, especially in psychostimulant addiction.

Going beyond video game consumption when considering Internet Gaming Disorder

BACKGROUND

Recognizing the crucial importance of understanding the impact of video games on health in today's gaming-dominated world, our study aimed to investigate the relationship between gaming time and Internet Gaming Disorder (IGD). Despite the widespread assumption that a connection exists between both, previous studies have revealed highly variable associations, highlighting significant weaknesses in establishing a robust link.

METHODS

To unravel this complex relationship, we recruited two independent samples of League of Legends players. We combined the collection of self-reported and actual gameplay data, together with assessments of mental health, personality traits, and cognitive abilities.

RESULTS

Surprisingly, none of the gaming variables demonstrated a robust and stable association with IGD, regardless of whether players spent less than or more than 30 hours per week gaming-a threshold suggested by the American Psychiatric Association as a potential indicator of disordered gaming. Notably, mental health factors, such as anxiety, depression and ADHD, emerged as the most influential predictors of IGD.

CONCLUSION

These findings, replicated across two independent samples, challenge the prevailing belief that limiting screen time alone effectively combats IGD. Instead, mental health factors play a crucial role in mitigating risks associated with gaming. Policies focusing solely on restricting screen time are insufficient in reducing the prevalence or symptoms of IGD. Rather, a comprehensive approach that considers mental health and key personality traits must be adopted to safeguard the well-being of individuals engaged in gaming.

Disruption of positive- and negative-feature morphine interoceptive occasion setters by dopamine receptor agonism and antagonism in male and female rats

RATIONALE

Internally perceived stimuli evoked by morphine administration can form Pavlovian associations such that they can function as occasion setters (OSs) for externally perceived reward cues in rats, coming to modulate reward-seeking behaviour. Though much research has investigated mechanisms underlying opioid-related reinforcement and analgesia, neurotransmitter systems involved in the functioning of opioids as Pavlovian interoceptive discriminative stimuli remain to be disentangled despite documented differences in the development of tolerance to analgesic versus discriminative stimulus effects.

OBJECTIVES

Dopamine has been implicated in many opioid-related behaviours, so we aimed to investigate the role of this neurotransmitter in expression of morphine occasion setting.

METHODS

Male and female rats were assigned to positive- (FP) or negative-feature (FN) groups and received an injection of morphine or saline before each training session. A 15-s white noise conditioned stimulus (CS) was presented 8 times during every training session; offset of this stimulus was followed by 4-s access to liquid sucrose on morphine, but not saline, sessions for FP rats. FN rats learned the reverse contingency. Following stable discrimination, rats began generalization testing for expression of morphine-guided sucrose seeking after systemic pretreatment with different doses of the non-selective dopamine receptor antagonist, flupenthixol, and the non-selective dopamine receptor agonist, apomorphine, combined with training doses of morphine or saline in a Latin-square design.

RESULTS

The morphine discrimination was acquired under both FP and FN contingencies by males and females. Neither flupenthixol nor apomorphine at any dose substituted for morphine, but both apomorphine and flupenthixol disrupted expression of the morphine OS. This inhibition was specific to sucrose seeking during CS presentations rather than during the period before CS onset and, in the case of apomorphine more so than flupenthixol, to trials on which access to sucrose was anticipated.

CONCLUSIONS

Our findings lend support to a mechanism of occasion setting involving gating of CS-induced dopamine release rather than by direct dopaminergic modulation by the morphine stimulus.