Translational and reverse translational research on the role of stress in drug craving and relapse

Fos expression in the periaqueductal gray, but not the ventromedial hypothalamus, is correlated with psychosocial stress-induced cocaine-seeking behavior in rats

Psychosocial stressors are known to promote cocaine craving and relapse in humans but are infrequently employed in preclinical relapse models. Consequently, the underlying neural circuitry by which these stressors drive cocaine seeking has not been thoroughly explored. Using Fos expression analyses, we sought to examine whether the ventromedial hypothalamus (VMH) or periaqueductal gray (PAG), two critical components of the brain's hypothalamic defense system, are activated during psychosocial stress-induced cocaine seeking. Adult male and female rats self-administered cocaine (0.5 mg/kg/inf IV, fixed-ratio 1 schedule, 2 h/session) over 20 sessions. On sessions 11, 14, 17, and 20, a tactile cue was present in the operant chamber that signaled impending social defeat stress (n=16, 8/sex), footshock stress (n=12, 6/sex), or a no-stress control condition (n=12, 6/sex) immediately after the session's conclusion. Responding was subsequently extinguished, and rats were tested for reinstatement of cocaine seeking during re-exposure to the tactile cue that signaled their impending stress/no-stress post-session event. All experimental groups displayed significant reinstatement of cocaine seeking, but Fos analyses indicated that neural activity within the rostrolateral PAG (rPAGl) was selectively correlated with cocaine-seeking magnitude in the socially-defeated rats. rPAGl activation was also associated with active-defense coping behaviors during social defeat encounters and with Fos expression in prelimbic prefrontal cortex and orexin-negative cells of the lateral hypothalamus/perifornical area in males, but not females. These findings suggest a potentially novel role for the rPAGl in psychosocial stress-induced cocaine seeking, perhaps in a sex-dependent manner.

Dehumanization of stigmatized targets of ostracism

The study explored people's reactions to observing the ostracism of stigmatized targets. Participants (n = 198) who observed ostracism experienced need threat regardless of the target's identity. Participants regarded included addicts more positively than ostracized addicts, especially on traits that are considered unique to humans. As for dehumanization, subtle measures demonstrate that ostracized targets are perceived as less human. In contrast, our original measure of blatant dehumanization suggests that targets of ostracism are perceived as more human. The study stresses the inconsistency between dehumanization measurements and the need to specify what each measure taps into and how each contributes to the theory.

The anxiogenic drug yohimbine is a reinforcer in male and female rats

The indole alkaloid yohimbine is an anxiogenic drug that activates stress-responsive systems in the brain. However, because yohimbine also elicits approach behaviors, this study employed male and female Sprague-Dawley rats to explore its potential reinforcing effects. Thus, it was first determined if intravenous (IV) infusions of yohimbine (0.25 mg/kg/infusion) could maintain lever pressing, whether intake could be modulated by dose/infusion, and if lever pressing would persist in the absence of yohimbine or yohimbine-paired cues. Next, to assess yohimbine's effect on memory consolidation, 0.3, 1.25 or 3 mg/kg yohimbine was administered post-training using an object recognition memory task. Finally, place conditioning assessed whether doses of yohimbine that elevate blood serum corticosterone levels (1.25 or 3 mg/kg) could elicit a conditioned place preference. It was found that both sexes acquired yohimbine IV self-administration, that intake was modulated by dose/infusion, and that lever pressing persisted during extinction and in the absence of the yohimbine-paired cue. As well, post-training injections of 1.25 mg/kg yohimbine enhanced consolidation of object memory, and 1.25 and 3 mg/kg elevated corticosterone levels and elicited a place preference in both sexes. Finally, in behavioral tests of psychomotor functions, acute yohimbine increased lever pressing for a visual cue and elevated locomotor activity. These findings reveal a profile of yohimbine's behavioral effects that is consistent with that of psychostimulant reinforcing drugs.

"They're not mentally ill, their lives are just shit": Stakeholders' understanding of deaths of despair in a deindustrialised community in North East England

The rise in mortality in high-income countries from drug, suicide, and alcohol specific causes, referred to collectively as 'deaths of despair', has received growing interest from researchers. In both the US and UK, mortality rates from deaths of despair are higher in deprived, deindustrialised communities. In this qualitative study, we sought to learn how stakeholders working with vulnerable populations in Middlesbrough, a deindustrialised town in North East England with above average mortality from deaths of despair, understand and explain the prevalence of deaths from these causes in their area. Participants identified a number of structural and socio-cultural determinants that they believe drive deaths of despair in their community, including the effects of austerity, deindustrialisation, communal identity, and collective trauma; we argue that these determinants are themselves a product of structural violence.

Basal cortisol level modulates stress-induced opioid-seeking behavior

In preclinical studies and our human laboratory, the α2-noradrenergic autoreceptor antagonist yohimbine was found to promote drug-seeking behavior. This study evaluated effects of dose-combinations of yohimbine and the glucocorticoid receptor agonist hydrocortisone to model intensity-dependent effects of stimulating each neurochemical system, alone and together, on stress-reactivity and opioid-seeking. Twelve regular heroin-using participants diagnosed with opioid use disorder (OUD) were stabilized on sublingual buprenorphine (8-mg/day), then passed a hydromorphone 18-mg vs. placebo intramuscular reinforcement screen. Across 9 experimental conditions (3 × 3 within-subject, randomized crossover, placebo-controlled, double-blind design) during inpatient buprenorphine maintenance, combinations of oral pretreatment doses of yohimbine (0, 27, 54-mg; t = 0 min) then hydrocortisone (0, 20, 40-mg; t = 45 min) were administered. In each condition, subjective drug and mood effects, cardiovascular responses, and saliva cortisol and α-amylase levels were assessed to evaluate stress-reactivity, and participants completed a 12-trial choice progressive ratio task during which they could earn units of hydromorphone (1.5-mg intramuscular) and/or money ($2.00). Yohimbine dose-dependently increased blood pressure, α-amylase, and anxiety scores, and decreased opioid agonist symptoms; hydrocortisone dose-dependently increased cortisol levels. Yohimbine/hydrocortisone dose-combinations significantly shifted within-session responding from money to opioid-seeking among participants with lower basal cortisol levels. These findings replicate yohimbine effects on stress biomarkers and demonstrate that noradrenergic/glucocorticoid-potentiated opioid-seeking is modulated by basal cortisol level. In persons with OUD stabilized on buprenorphine, basal HPA-axis activity and acute stressors can enhance opioid relative reinforcing efficacy. These factors may limit OUD treatment efficacy and highlight the need for novel interventions that prevent stress-induced opioid-seeking.

Self-control as mediator and social support as moderator in stress-relapse dynamics of substance dependency

Substance Use Disorders (SUDs) present a significant challenge to global public health, with prolonged drug use not only impairing individual health but also hindering social development. Despite various interventions aimed at addressing drug abuse and dependence, a high relapse rate remains a prominent issue. In light of this, this study aims to explore the impact of perceived stress on the relapse of individuals with SUDs, as well as the mediating role of self-control and the moderating role of social support, in hopes of providing new perspectives for interventions to reduce the risk of relapse among individuals with SUDs. By utilizing a convenience sampling method, 420 male individuals with SUDs were recruited from detoxification centers in Guangxi, China. They completed questionnaires on perceived stress, self-control, social support, and tendencies towards relapse. A total of 401 valid datasets were obtained and analyzed using the SPSS Process plugin to conduct a moderated mediation model analysis. Results: (1) Perceived stress had a positive impact on the relapse of individuals with SUDs, (2) Self-control played a partial mediating role between perceived stress and the relapse, (3) The direct effect of perceived stress on the relapse and its first half of the indirect effect were moderated by social support. The research emphasize the critical importance of learning stress management strategies, enhancing self-control, and receiving comprehensive social support in the prevention and treatment of substance dependence. By strengthening self-control and social support as both internal and external resources, the likelihood of relapse among individuals with SUDs can be reduced, contributing to more effective and comprehensive drug rehabilitation strategies.

A large-scale c-Fos brain mapping study on extinction of cocaine-primed reinstatement

Individuals with cocaine addiction can experience many craving episodes and subsequent relapses, which represents the main obstacle to recovery. Craving is often favored when abstinent individuals ingest a small dose of cocaine, encounter cues associated with drug use or are exposed to stressors. Using a cocaine-primed reinstatement model in rat, we recently showed that cocaine-conditioned interoceptive cues can be extinguished with repeated cocaine priming in the absence of drug reinforcement, a phenomenon we called extinction of cocaine priming. Here, we applied a large-scale c-Fos brain mapping approach following extinction of cocaine priming in male rats to identify brain regions implicated in processing the conditioned interoceptive stimuli of cocaine priming. We found that cocaine-primed reinstatement is associated with increased c-Fos expression in key brain regions (e.g., dorsal and ventral striatum, several prefrontal areas and insular cortex), while its extinction mostly disengages them. Moreover, while reinstatement behavior was correlated with insular and accumbal activation, extinction of cocaine priming implicated parts of the ventral pallidum, the mediodorsal thalamus and the median raphe. These brain patterns of activation and inhibition suggest that after repeated priming, interoceptive signals lose their conditioned discriminative properties and that action-outcome associations systems are mobilized in search for new contingencies, a brain state that may predispose to rapid relapse.

The estrous cycle has no effect on incubation of methamphetamine craving and associated Fos expression in dorsomedial striatum and anterior intralaminar nucleus of thalamus

Relapse is a major challenge in treating drug addiction, and drug seeking progressively increases after abstinence, a phenomenon termed "incubation of drug craving". Previous studies demonstrated both sex differences and an effect of estrous cycle in female rats in incubation of cocaine craving. In contrast, while incubation of methamphetamine craving is similar across sexes, whether estrous cycle plays a role in this incubation has yet to be fully addressed. Moreover, whether neural mechanisms underlying incubation of methamphetamine craving differ across estrous cycles is largely unknown. To address these gaps, we first compared methamphetamine self-administration, and methamphetamine seeking on both abstinence days 1 and 28 between male rats and female rats across the estrous cycle. Next, we examined neuronal activation associated with incubated methamphetamine seeking in dorsomedial striatum (DMS) and lateral portion of the anterior intralaminar nucleus of thalamus (AIT-L), two brain areas previously implicated in incubation of methamphetamine craving. We found no effect of sex or estrous cycle on methamphetamine self-administration and methamphetamine seeking on abstinence days 1 and 28. We also found no effect of sex or estrous cycle on the number of Fos-expressing cells in DMS or AIT-L following methamphetamine seeking test. Taken together, our results showed that methamphetamine self-administration and incubation of methamphetamine craving was not dependent on sex or estrous cycles under our experimental condition, and the role of DMS and AIT-L in incubation of methamphetamine craving may be similar across sexes and across estrous cycles in female rats.

Neural Correlates of Stress and Alcohol Cue-Induced Alcohol Craving and of Future Heavy Drinking: Evidence of Sex Differences

OBJECTIVE

Stress and alcohol cue reactivity are associated with poor treatment outcomes in alcohol use disorder (AUD), but sex-specific neural correlates of stress and alcohol cue-induced craving compared with neutral cue-induced craving and of heavy drinking outcomes in AUD have not been examined. Thus, this study prospectively examined these associations and assessed sex differences.

METHODS

Treatment-seeking adults with AUD (N=77; 46 men and 31 women) completed a functional MRI task involving stress, alcohol, and neutral cue exposure with repeated assessments of alcohol craving. Most of these participants (N=72; 43 men and 29 women) then participated in an 8-week standardized behavioral AUD treatment program, during which the percentage of heavy drinking days was assessed.

RESULTS

Significant increases in both stress and alcohol cue-induced craving relative to neutral cue-induced craving were observed, with a greater alcohol-neutral contrast in craving relative to the stress-neutral contrast among men and equivalent stress-neutral and alcohol-neutral contrasts in craving among women. Whole-brain voxel-based regression analyses showed craving-associated hyperactivation in the neutral condition, but hypoactive prefrontal (ventromedial and lateral prefrontal, supplementary motor, and anterior cingulate regions) and striatal responses during exposure to stressful images (stress-neutral contrast) and alcohol cues (alcohol-neutral contrast), with significant sex differences. Additionally, a higher percentage of heavy drinking days was associated with hypoactivation of the subgenual anterior cingulate cortex and the bed nucleus of the stria terminalis in the stress-neutral contrast among women, hyperactivation of the hypothalamus in the stress-neutral contrast among men, and hyperactivation of the hippocampus in the alcohol-neutral contrast among men.

CONCLUSIONS

Sex differences in stress- and alcohol cue-induced responses in the cortico-striatal-limbic network related to subjective alcohol craving and to heavy drinking indicated that distinct brain circuits underlie alcohol use outcomes in women and men. These findings underscore the need for sex-specific therapeutics to address this neural dysfunction effectively.

The effect of chronic stress on the immunogenicity and immunoprotection of the M6-TT vaccine in female mice

Active vaccination is an effective therapeutic option to reduce the reinforcing effects of opioids. Several studies showed that chronic stress affects the immune system decreasing the efficiency of some vaccines. Heroin withdrawal is a stressor and it is a stage in which the patient who abuses heroin is vulnerable to stress affects the immune response and consequently its immunoprotective capacity, then, the objective was to determine the effect of heroin-withdrawal and heroin-withdrawal plus immobilization, on the immune (immunogenicity) and protective response (behavioral response) of morphine-6-hemisuccinate-tetanus toxoid (M6-TT) vaccine in animals of two inbred mice strains with different sensitivity to drug-opioid and stress. Female BALB/c and C57Bl/6 inbred mice were immunized with the M6-TT. A solid-phase antibody-capture ELISA was used to monitor antibody titer responses after each booster dose in vaccinated animals. During the vaccination period, the animals were subjected to two different stress conditions: drug-withdrawal (DW) and immobilization (IMM). The study used tail-flick testing to evaluate the heroin-induced antinociceptive effects. Additionally, heroin-induced locomotor activity was evaluated. Stress decreased the heroin-specific antibody titer generated by the M6-TT vaccine in the two inbred mouse strains evaluated. In the two stress conditions, the antibody titer was not able to decrease the heroin-induced antinociceptive effects and locomotor activity. These findings suggest that stress decreases the production of antibodies and the immunoprotective capacity of the M6-TT vaccine. This observation is important to determine the efficacy of active vaccination as a potential therapy for patients with opioid drug use disorder, since these patients during drug-withdrawal present stress disorders, which could affect the efficacy of therapy such as active vaccination.

Re-Purposing FDA-Approved Drugs for Opioid Use Disorder

OBJECTIVE

To investigate FDA-approved drugs prescribed for unrelated diseases or conditions that promote remission in subjects diagnosed with opioid use disorder (OUD).

METHODS

This was a retrospective observational study utilizing the TriNetX electronic medical record data. Subjects between 18 and 65 years old were included in this study. First, a drug screen was employed to identify medications used for chronic illness that are associated with OUD remission. Based on Fisher's exact test for significance, 28 of 101 medications were selected for further analysis. Positive (buprenorphine/methadone) and negative controls (benazepril) were included in the analysis. Medications were analyzed in the absence and presence of buprenorphine or methadone, two medications used to treat OUD, to identify the likelihood of OUD remission up to one year following the index event.

RESULTS

We identify 8 medications (prazosin, propranolol, lithium carbonate, olanzapine, quetiapine, bupropion, citalopram, and escitalopram) that may be useful for increasing remission in OUD in the absence of buprenorphine or methadone. Additionally, our results identify psychiatric medications that when taken alongside buprenorphine and methadone improve remission rates.

CONCLUSION

These results provide medication options that may be useful in treating OUD as well as integrated therapies to treat comorbid mental illness.

Opioid withdrawal: role in addiction and neural mechanisms

Withdrawal from opioids involves a negative affective state that promotes maintenance of drug-seeking behavior and relapse. As such, understanding the neurobiological mechanisms underlying withdrawal from opioid drugs is critical as scientists and clinicians seek to develop new treatments and therapies. In this review, we focus on the neural systems known to mediate the affective and somatic signs and symptoms of opioid withdrawal, including the mesolimbic dopaminergic system, basolateral amygdala, extended amygdala, and brain and hormonal stress systems. Evidence from preclinical studies suggests that these systems are altered following opioid exposure and that these changes mediate behavioral signs of negative affect such as aversion and anxiety during withdrawal. Adaptations in these systems also parallel the behavioral and psychological features of opioid use disorder (OUD), highlighting the important role of withdrawal in the development of addictive behavior. Implications for relapse and treatment are discussed as well as promising avenues for future research, with the hope of promoting continued progress toward characterizing neural contributors to opioid withdrawal and compulsive opioid use.

Orbitofrontal cortex microRNAs support long-lasting heroin seeking behavior in male rats

Recovery from opioid use disorder (OUD) and maintenance of abstinence from opioid use is hampered by perseverant drug cravings that may persist for months after cessation of drug use. Drug cravings can intensify during the abstinence period, a phenomenon referred to as the 'incubation of craving' that has been well-described in preclinical studies. We previously reported that animals that self-administered heroin at a dosage of 0.075 mg/kg/infusion (HH) paired with discrete drug cues displayed robust incubation of heroin craving behavior after 21 days (D) of forced abstinence, an effect that was not observed with a lower dosage (0.03 mg/kg/infusion; HL). Here, we sought to elucidate molecular mechanisms underlying long-term heroin seeking behavior by profiling microRNA (miRNA) pathways in the orbitofrontal cortex (OFC), a brain region that modulates incubation of heroin seeking. miRNAs are small noncoding RNAs with long half-lives that have emerged as critical regulators of drug seeking behavior but their expression in the OFC has not been examined in any drug exposure paradigm. We employed next generation sequencing to detect OFC miRNAs differentially expressed after 21D of forced abstinence between HH and HL animals, and proteomics analysis to elucidate miRNA-dependent translational neuroadaptations. We identified 55 OFC miRNAs associated with incubation of heroin craving, including miR-485-5p, which was significantly downregulated following 21D forced abstinence in HH but not HL animals. We bidirectionally manipulated miR-485-5p in the OFC to demonstrate that miR-485-5p can regulate long-lasting heroin seeking behavior after extended forced abstinence. Proteomics analysis identified 45 proteins selectively regulated in the OFC of HH but not HL animals that underwent 21D forced abstinence, of which 7 were putative miR-485-5p target genes. Thus, the miR-485-5p pathway is dysregulated in animals with a phenotype of persistent heroin craving behavior and OFC miR-485-5p pathways may function to support long-lasting heroin seeking.

Reframing caring for parents who struggle with substance-use disorders

Nancy Suchman and the colleagues she influenced have produced ground-breaking and attitude-challenging work in understanding how parenting and substance use come together. Dr Suchman and her colleagues make the claim that there is nothing about a substance-use disorder that precludes effective and sensitive caring for children especially with interventions that focus on the parent-child relationship. Suchman's legacy is to highlight how substance use as an illness pulls individuals away from important, caring relationships and limits their giving themselves to those relationships. Restoring the salience of caring relationships and of the individual's ability to care may be as impactful on their substance use as a strict focus on the reduction of drug use and achieving abstinence.

Acute food deprivation-induced relapse to heroin seeking after short and long punishment-imposed abstinence in male rats

RATIONAL

Stress is a major trigger for drug relapse in humans and animal models, even after prolonged abstinence. However, animal models for stress-induced relapse were criticized for the lack of predictive and face validity.

OBJECTIVES

Here we investigated the effect of acute food deprivation stress in a novel stress-induced relapse model using voluntary, punishment-imposed abstinence from heroin. We also performed a detailed characterization of the development of punishment-imposed abstinence.

METHODS

Male rats were trained to self-administered heroin (0.1 mg/kg/infusion) for 2 weeks, using the seeking-taking chained schedule. Pressing the 'seeking' lever led to the insertion of the 'taking' lever and pressing the take lever resulted in heroin infusion. Following self-administration training, rats were exposed to 8 or 21 days of heroin-seeking punishment. During punishment, 30% of the completed seek links resulted in a mild escalating footshock instead of take lever presentation. Next, rats were tested for heroin seeking under extinction conditions after 24 h of food deprivation and sated conditions.

RESULTS

Probabilistic punishment of seeking lever responses resulted in gradual suppression of heroin seeking and taking. Exposure to food-deprivation stress induced a robust relapse to heroin seeking after short and long punishment-imposed abstinence periods, without significant effects of time, i.e., no incubation of heroin seeking. Individual differences were observed in the development of punishment-induced abstinence and stress-induced relapse.

CONCLUSIONS

These results suggest that stress is a reliable trigger to relapse even after a prolonged period of punishment-induced, voluntary abstinence.

Effects of neuromodulation on cognitive and emotional responses to psychosocial stressors in healthy humans

Physiological and psychological stressors can exert wide-ranging effects on the human brain and behavior. Research has improved understanding of how the sympatho-adreno-medullary (SAM) and hypothalamic-pituitary-adrenocortical (HPA) axes respond to stressors and the differential responses that occur depending on stressor type. Although the physiological function of SAM and HPA responses is to promote survival and safety, exaggerated psychobiological reactivity can occur in psychiatric disorders. Exaggerated reactivity may occur more for certain types of stressors, specifically, psychosocial stressors. Understanding stressor effects and how the body regulates these responses can provide insight into ways that psychobiological reactivity can be modulated. Non-invasive neuromodulation is one way that responding to stressors may be altered; research into these interventions may provide further insights into the brain circuits that modulate stress reactivity. This review focuses on the effects of acute psychosocial stressors and how neuromodulation might be effective in altering stress reactivity. Although considerable research into stress interventions focuses on treating pathology, it is imperative to first understand these mechanisms in non-clinical populations; therefore, this review will emphasize populations with no known pathology and consider how these results may translate to those with psychiatric pathologies.

Sex-dependent effects of chronic stress on punished cocaine self-administration and cue-induced relapse to cocaine seeking

We tested the effects of chronic stress on cocaine relapse after drug-reinforced responding was suppressed by punishment, an animal model of human relapse after self-imposed abstinence due to the negative consequences of drug use. Male rats displayed greater resistance to punishment than females, but daily stress decreased this resistance. Only female rats with a history of chronic stress displayed increased responding for cocaine cues from abstinence Day 1 to Day 8. Thus, the effects of chronic stress on punished cocaine self-administration and cue-induced relapse are dependent on biological sex, and may have implications for more targeted treatments for cocaine addiction.

Effects of resilience on impulsivity, cognition and depression during protracted withdrawal among Chinese male methamphetamine users

BACKGROUND

Methamphetamine (METH) dependence is a complex and dynamic public health problem. Long-term abuse of METH can increase numerous risks of mental and physical problems. Currently, the methods to reduce METH dependence and improve the withdrawal symptoms are limited and ineffective. Resilience is seen as a multidimensional and dynamic capability to recover or bounce back from stressful events and is also generally considered as a protective factor against mental dysfunction.

METHODS

One hundred thirty-four males with METH dependence were consecutively recruited from Huanglong Compulsory Isolated Detoxification Center between 2019 and 2021, of whom 112 were into the group. The Connor-Davidson Resilience Scale (CD-RISC), Self-rating depression scale (SDS), Self-rating anxiety scale (SAS), Barratt Impulsiveness Scale-11(BIS-11), and the Repeatable Battery for the Assessment of Neuropsychological Status (Rbans) were used to evaluate resilience, depression, anxiety, impulsivity, and cognition respectively.

RESULTS

The results mainly indicated that high resilience group showed lower SDS, SAS and BIS-11 scores than low resilience group (all p < 0.05). Besides, the total scores of Rbans were higher in high resilience groups than low resilience group (both p < 0.05). Moreover, linear regression results showed that resilience may be influenced by the scores of SDS and SAS.

CONCLUSIONS

Resilience is negatively correlated with impulsivity and depression. Besides, it is also positively associated with cognitive function. Drug users with higher resilience may have a strong ability to mobilize psychological resources to create a good psychological environment, which may have a positive effect on the relief or improvement of symptoms.

A Pilot Randomized Control Study on Effect Brief Heart Rate Variability Biofeedback as a Complementary Treatment in Men with Methamphetamine Use Disorder

The aims of this study were to investigate the efficacy of heart rate variability biofeedback (HRVBFB) intervention in terms of reducing craving, severity of dependence, and rate of positive methamphetamine urine testing in men taking part in a methamphetamine use disorder outpatient treatment program. Sixty-one adult men received either HRVBFB treatment plus treatment as usual (TAU) over four weeks or TAU only. Men receiving HRVBFB showed significantly greater reductions in craving, dependence severity, and the rate of positive methamphetamine urine testing at the end of the intervention and four weeks of follow-up. The analyses further showed that the levels of craving and dependence severity at treatment entry were predictive of changes in craving and dependence severity at the end of treatment and follow-up, respectively. The baseline status of a positive methamphetamine urine test only predicted a positive methamphetamine urine test at the end of treatment, not at the end of the follow-up period. Our results showed HRVBFB intervention has merits as an adjunct treatment to ameliorate cravings and reduce the severity of dependence experienced by persons with methamphetamine use disorder. An added value of HRVBFB intervention is the fact that it can be easily and affordably implemented in everyday life.

Prevention of relapse to methamphetamine self-administration by environmental enrichment: involvement of glucocorticoid receptors

RATIONALE

In rodents, environmental enrichment (EE) produces both preventive and curative effects on drug addiction, and this effect is believed to depend at least in part on EE's actions on the stress system.

OBJECTIVES

This study investigated whether exposure to EE during abstinence reduces methamphetamine seeking after extended self-administration. In addition, we investigated whether these effects are associated with alterations in the levels of glucocorticoid receptors (GR) in the brain and whether administration of GR antagonists blocks methamphetamine relapse.

METHODS

We allowed rats to self-administer methamphetamine for twenty 14-h sessions. After 3 weeks of abstinence either in standard (SE) or EE conditions, we measured methamphetamine seeking in a single 3-h session. Then, we used western blot techniques to measure GR levels in several brain areas. Finally, in an independent group of rats, after methamphetamine self-administration and abstinence in SE, we administered the GR antagonist mifepristone, and we investigated methamphetamine seeking.

RESULTS

Exposure to EE reduced methamphetamine seeking and reversed methamphetamine-induced increases in GR levels in the ventral and dorsal hippocampus. In addition, EE decreased GR levels in the amygdala in drug-naive animals, but this effect was prevented by previous exposure to methamphetamine. Administration of mifepristone significantly decreased methamphetamine seeking.

CONCLUSIONS

The anti-craving effects of EE are paralleled by restoration of methamphetamine-induced dysregulation of GR in the hippocampus. These results provide support for the hypothesis that the effect of EE on methamphetamine relapse is at least in part mediated by EE's action on the brain stress system.

Opioid and Sucrose Craving Are Accompanied by Unique Behavioral and Affective Profiles after Extended Abstinence in Male and Female Rats

Incubation of craving refers to the intensification of drug-seeking behavior in response to reward-paired cues over the course of abstinence. In rodents, craving and drug-seeking behaviors have been measured by an increase in lever pressing in the absence of reinforcer availability in response to cue presentations. However, craving in rodents is difficult to define and little is known about the behavioral signatures that accompany increased drug-seeking behavior measured by lever pressing. The affective components of relapse are also important, but understudied in rodents. Hormonal fluctuations influence craving for psychostimulants, but little is known about the impact of the estrous cycle on opioid-seeking behavior. This study sought to delineate the behavioral and affective signatures associated with craving, and to examine the influence of the female estrous cycle on craving. Male and female rats underwent 10 d of intravenous opioid self-administration. Separate cohorts of control rats self-administered oral sucrose, a natural nondrug reward. Cue-induced seeking tests were conducted after 1 or 30d of forced abstinence. These sessions were recorded and scored for overall locomotion, instances of sniffing, grooming, or hyperactivity. Ultrasonic vocalizations (USVs) were also recorded to determine affective profiles that accompany opioid seeking. Although active lever presses and overall locomotion increased unanimously over extended abstinence from heroin and sucrose, a sex- and reinforcer-specific behavioral and affective signature of craving emerged. Furthermore, although the female estrous cycle did not affect taking or seeking, it appears to influence more granular behaviors.

Sex Differences in Opioid and Psychostimulant Craving and Relapse: A Critical Review

A widely held dogma in the preclinical addiction field is that females are more vulnerable than males to drug craving and relapse. Here, we first review clinical studies on sex differences in psychostimulant and opioid craving and relapse. Next, we review preclinical studies on sex differences in psychostimulant and opioid reinstatement of drug seeking after extinction of drug self-administration, and incubation of drug craving (time-dependent increase in drug seeking during abstinence). We also discuss ovarian hormones' role in relapse and craving in humans and animal models and speculate on brain mechanisms underlying their role in cocaine craving and relapse in rodent models. Finally, we discuss imaging studies on brain responses to cocaine cues and stress in men and women.The results of the clinical studies reviewed do not appear to support the notion that women are more vulnerable to psychostimulant and opioid craving and relapse. However, this conclusion is tentative because most of the studies reviewed were correlational, not sufficiently powered, and not a priori designed to detect sex differences. Additionally, imaging studies suggest sex differences in brain responses to cocaine cues and stress. The results of the preclinical studies reviewed provide evidence for sex differences in stress-induced reinstatement and incubation of cocaine craving but not cue- or cocaine-induced reinstatement of cocaine seeking. These sex differences are modulated in part by ovarian hormones. In contrast, the available data do not support the notion of sex differences in craving and relapse/reinstatement for methamphetamine or opioids in rodent models. SIGNIFICANCE STATEMENT: This systematic review summarizes clinical and preclinical studies on sex differences in psychostimulant and opioid craving and relapse. Results of the clinical studies reviewed do not appear to support the notion that women are more vulnerable to psychostimulant and opioid craving and relapse. Results of preclinical studies reviewed provide evidence for sex differences in reinstatement and incubation of cocaine seeking but not for reinstatement or incubation of methamphetamine or opioid seeking.

Deconstructing and reconstructing behaviour relevant to mental health disorders: The benefits of a psychological approach, with a focus on addiction

RUTHERFORD, L.G. and Milton, A.L. Deconstructing and reconstructing behaviour relevant to mental health disorders: what can psychology offer? NEUROSCI BIOBEHAV REV XX(X)XXX-XXX, 2021. - Current treatments for mental health disorders are successful only for some patients, and there is an unmet clinical need for new treatment development. One challenge for treatment development has been how best to model complex human conditions in animals, where mechanism can be more readily studied with a range of neuroscientific techniques. We suggest that an approach to modelling based on associative animal learning theory provides a good framework for deconstructing complex mental health disorders such that they can be studied in animals. These individual simple models can subsequently be used in combination to 'reconstruct' a more complex model of the mental health disorder of interest. Using examples primarily from the field of drug addiction, we explore the 'psychological approach' and suggest that in addition to facilitating translation and backtranslation of tasks between animal models and patients, it is also highly concordant with the concept of triangulation.

Factors modulating the incubation of drug and non-drug craving and their clinical implications

It was suggested in 1986 that cue-induced cocaine craving increases progressively during early abstinence and remains high during extended periods of time. Clinical evidence now supports this hypothesis and that this increase is not specific to cocaine but rather generalize across several drugs of abuse. Investigators have identified an analogous incubation phenomenon in rodents, in which time-dependent increases in cue-induced drug seeking are observed after abstinence from intravenous drug or palatable food self-administration. Incubation of craving is susceptible to variation in magnitude as a function of biological and/or the environmental circumstances surrounding the individual. During the last decade, the neurobiological correlates of the modulatory role of biological (sex, age, genetic factors) and environmental factors (environmental enrichment and physical exercise, sleep architecture, acute and chronic stress, abstinence reinforcement procedures) on incubation of drug craving has been investigated. In this review, we summarized the behavioral procedures adopted, the key underlying neurobiological correlates and clinical implications of these studies.

Adolescent neuroimmune function and its interaction with alcohol

Adolescence is an evolutionarily conserved developmental period associated with behavioral change, including increased risk-taking and alcohol use. Experimentation with alcohol typically begins in adolescence and transitions to binge-like patterns of consumption. Alcohol exposure during adolescence can alter normative changes in brain structure and function. Understanding mechanisms by which ethanol impacts neurodevelopmental processes is important for preventing and ameliorating the deleterious consequences of adolescent alcohol abuse. This review focuses on the neuroimmune system as a key contributor to ethanol-induced changes in adolescent brain and behavior. After brief review of neuroimmune system development, acute and chronic effects of ethanol on adolescent neuroimmune functioning are addressed. Comparisons between stress/immunological challenges and ethanol on adolescent neuroimmunity are reviewed, as cross-sensitization is relevant during adolescence. The mechanisms by which ethanol alters neuroimmune functioning are then discussed, as they may portend development of neuropathological consequences and thus increase vulnerability to subsequent challenges and potentiate addictive behaviors.

The impact of social variables in preclinical models of cocaine abuse

At present, there are no US Food and Drug Administration–approved treatments for cocaine use disorders. One consideration for this lack of treatment efficacy stems from the appropriate use of animal models. The premise of this commentary is that social behavior needs to be incorporated in animal models of cocaine use disorder. The goal of this commentary is to describe some of the strengths and limitations of recent preclinical animal models of cocaine abuse which have incorporated social behavior. There are many ways to include social variables into preclinical research, and the study design will depend on the questions asked. Four general types of studies incorporating social factors are described: those involving aggression (that is, maternal neglect and social defeat), modeling, social reward, and social housing, including social isolation. The inclusion of social variables into preclinical research will help identify biobehavioral markers that may lead to an individualized treatment approach that more effectively decreases cocaine use. These studies will aid in the development of novel pharmacotherapies as well as non-pharmacological interventions (for example, punishment, alternative reinforcers, and environmental enrichment) that would be critical for informing policy decisions.

The instigating effects of isolation on substance-related intimate partner violence: A review

In this article, we examine the empirical and theoretical support for the idea that experiences of isolation can intensify substance use, even among those in committed close relationships, and can increase the likelihood of negative conflict behaviors, including intimate partner violence (IPV). Cross-sectional, longitudinal, and laboratory-based research suggest that individuals and couples who report experiences of social exclusion and have fewer social supports experience more mental health problems, more negative emotional experiences, and higher levels of stress. These negative outcomes spur coping efforts to reduce these distressing states, which often involve pain-relieving substances such as alcohol. We describe how dynamic models of relationship conflict and IPV can integrate alcohol and substance use patterns among both individuals and couples to understand and predict contexts leading to conflict escalation and IPV perpetration.

Consideration of sex as a biological variable in the translation of pharmacotherapy for stress-associated drug seeking

Stress is a frequent precipitant of relapse to drug use. Pharmacotherapies targeting a diverse array of neural systems have been assayed for efficacy in attenuating stress-induced drug-seeking in both rodents and in humans, but none have shown enough evidence of utility to warrant routine use in the clinic. We posit that a critical barrier in effective translation is inattention to sex as a biological variable at all phases of the research process. In this review, we detail the neurobiological systems implicated in stress-induced relapse to cocaine, opioids, methamphetamine, and cannabis, as well as the pharmacotherapies that have been used to target these systems in rodent models, the human laboratory, and in clinical trials. In each of these areas we additionally describe the potential influences of biological sex on outcomes, and how inattention to fundamental sex differences can lead to biases during drug development that contribute to the limited success of large clinical trials. Based on these observations, we determine that of the pharmacotherapies discussed only α₂-adrenergic receptor agonists and oxytocin have a body of research with sufficient consideration of biological sex to warrant further clinical evaluation. Pharmacotherapies that target β-adrenergic receptors, other neuroactive peptides, the hypothalamic-pituitary-adrenal axis, neuroactive steroids, and the endogenous opioid and cannabinoid systems require further assessment in females at the preclinical and human laboratory levels before progression to clinical trials can be recommended.

Impact of Acute and Chronic Cannabis Use on Stress Response Regulation: Challenging the Belief That Cannabis Is an Effective Method for Coping

Although research has only recently started to examine the impact of cannabis use on stress response, there is some evidence that indicates acute and chronic impacts of cannabis on these processes. In this paper, we review processes involved in regulating the stress response and we review the influence of acute and chronic exposure to cannabis on patterns and regulation of the stress response. We also highlight the role of stress as a risk factor for initiation and maintenance of cannabis use. In this context, we examine moderating variables, including sex and life adversity. In light of recent observations indicating increasing prevalence of cannabis use during pregnancy, we provide additional focus on cannabis use in this vulnerable population, including how acute and chronic stress may predispose some individuals to use cannabis during pregnancy. While this line of research is in its infancy, we review available articles that focus on the perinatal period and that examined the association between cannabis use and various life stressors, including partner violence, job loss, and lack of housing. We also review psychiatric co-morbidities (e.g., post-traumatic stress disorder, anxiety). A better understanding of the way stress and cannabis use relate within the general population, as well as within certain subgroups that may be at a greater risk of using and/or at greater risk for adverse outcomes of use, may lead to the development of novel prevention and intervention approaches.

Animal Models of Drug Relapse and Craving after Voluntary Abstinence: A Review

Relapse to drug use during abstinence is a defining feature of addiction. During the last several decades, this clinical scenario has been studied at the preclinical level using classic relapse/reinstatement models in which drug seeking is assessed after experimenter-imposed home-cage forced abstinence or extinction of the drug-reinforced responding in the self-administration chambers. To date, however, results from studies using rat relapse/reinstatement models have yet to result in Food and Drug Administration-approved medications for relapse prevention. The reasons for this state of affairs are complex and multifaceted, but one potential reason is that, in humans, abstinence is often self-imposed or voluntary and occurs either because the negative consequences of drug use outweigh the drug's rewarding effects or because of the availability of nondrug alternative rewards that are chosen over the drug. Based on these considerations, we and others have recently developed rat models of relapse after voluntary abstinence, achieved either by introducing adverse consequences to drug taking (punishment) or seeking (electric barrier) or by providing mutually exclusive choices between the self-administered drug and nondrug rewards (palatable food or social interaction). In this review, we provide an overview of these translationally relevant relapse models and discuss recent neuropharmacological findings from studies using these models. We also discuss sex as a biological variable, future directions, and clinical implications of results from relapse studies using voluntary abstinence models. Our main conclusion is that the neuropharmacological mechanisms controlling relapse to drug seeking after voluntary abstinence are often different from the mechanisms controlling relapse after home-cage forced abstinence or reinstatement after extinction. SIGNIFICANCE STATEMENT: This review describes recently developed rat models of relapse after voluntary abstinence, achieved either by introducing adverse consequences to drug taking or seeking or by providing mutually exclusive choices between the self-administered drug and nondrug rewards. This review discusses recent neuropharmacological findings from studies using these models and discusses future directions and clinical implications.

The Adenosine A2A Receptor Activation in Nucleus Accumbens Suppress Cue-Induced Reinstatement of Propofol Self-administration in Rats

Propofol has shown strong addictive properties in rats and humans. Adenosine A2A receptors (A2AR) in the nucleus accumbens (NAc) modulate dopamine signal and addictive behaviors such as cocaine- and amphetamine-induced self-administration. However, whether A2AR can modulate propofol addiction remains unknown. AAV-shA2AR was intra-NAc injected 3 weeks before the propofol self-administration training to test the impacts of NAc A2AR on establishing the self-administration model with fixed ratio 1 (FR1) schedule. Thereafter, the rats were withdrawal from propofol for 14 days and tested cue-induced reinstatement of propofol seeking behavior on day 15. The propofol withdrawal rats received one of the doses of CGS21680 (A2AR agonist, 2.5-10.0 ng/site), MSX-3 (A2AR antagonist, 5.0-20.0 μg/site) or eticlopride (D2 receptor (D2R) antagonist, 0.75-3.0 μg/site) or vehicle via intra-NAc injection before relapse behavior test. The numbers of active and inactive nose-poke response were recorded. Focal knockdown A2AR by shA2AR did not affect the acquisition of propofol self-administration behavior, but enhance cue-induced reinstatement of propofol self-administration compared with the AAV-shCTRLgroup. Pharmacological activation of the A2AR by CGS21680 (≥ 5.0 ng/site) attenuated cue-induced reinstatement of propofol self-administration behavior. Similarly, pharmacological blockade of D2R by eticlopride (0.75-3.0 μg/site) attenuated propofol seeking behavior. These effects were reversed by the administration of MSX-3 (5.0-20.0 μg/site). The A2AR- and D2R-mediated effects on propofol relapse were not confounded by the learning process, and motor activity as the sucrose self-administration and locomotor activity were not affected by all the treatments. This study provides genetic and pharmacological evidence that NAc A2AR activation suppresses cue-induced propofol relapse in rats, possibly by interacting with D2R.

The 5-HT2C receptor as a therapeutic target for alcohol and methamphetamine use disorders: A pilot study in treatment-seeking individuals

Alcohol use disorder (AUD) and methamphetamine use disorder (MUD) are prevalent and have high adverse impacts on both the individual and society. Current treatment strategies for these disorders are ineffective at a population level. Lorcaserin, a 5‐HT_2C receptor agonist, has shown potential at reducing the symptoms of substance use disorder. This pilot study (initiated prior to market withdrawal) examined feasibility and safety of lorcaserin treatment in people undergoing residential detoxification and treatment for AUD and MUD. This was an open label pilot study of lorcaserin where participants (n = 10 AUD; n = 8 MUD) received 10‐mg lorcaserin daily for 4 days then twice daily for 1 month. Primary outcome measures included recruitment and retention rate, incidence of treatment‐emergent events, incidence of methamphetamine or alcohol withdrawal‐related events, heart rate, and blood pressure. Secondary measures included pharmacokinetic data and self‐reported alcohol or methamphetamine use, craving, and psychological distress. AUD participants were recruited faster and had a greater retention rate compared with MUD participants. Lorcaserin did not alter vital signs, was well tolerated, and had a similar pharmacokinetic profile to individuals with obesity. Lorcaserin reduced self‐reported alcohol and amphetamine‐type substance use and craving in AUD and MUD participants, respectively. Self‐reported psychological health also improved over the treatment period for all participants. Despite the pilot nature of this study, our data support the notion of 5‐HT_2C receptors as a therapeutic target for drug and alcohol abuse.

Functional evaluation of NK1 antagonism on cue reactivity in opiate dependence; An fMRI study

BACKGROUND

Opiate addiction is a major health challenge with substantial societal cost. Though harm minimisation strategies have been effective, there is a growing need for new treatments for detoxification and relapse prevention. Preclinical research has found neurokinin 1 (NK1) receptors have prominent effects on opiate reward and reinforcement, and human studies have found NK1 antagonism led to reductions in craving and withdrawal. However, its effect on brain mechanisms in opiate addiction has not yet been examined.

METHODS

This study aims to assess the impact of NK1 antagonist aprepitant on heroin cue-elicited changes in blood-oxygenation level dependent (BOLD) signal in opiate dependent individuals undergoing detoxification. Participants will attend two scanning sessions and receive a single dose of aprepitant (320 mg) and a placebo in a randomised, cross-over design. During functional magnetic resonance imaging participants will undergo two runs of a cue reactivity task, which consists of passive viewing of drug cues or neutral cues in a block design fashion. We hypothesise that NK1 antagonism will attenuate the BOLD response to drug cues in the caudate nucleus and amygdala. Regions of interest were selected based on NK1 receptor density and their role in cue reactivity and craving.

Social interaction reward in rats has anti-stress effects

Social interaction in an alternative context can be beneficial against drugs of abuse. Stress is known to be a risk factor that can exacerbate the effects of addictive drugs. In this study, we investigated whether the positive effects of social interaction are mediated through a decrease in stress levels. For that purpose, rats were trained to express cocaine or social interaction conditioned place preference (CPP). Behavioural, hormonal, and molecular stress markers were evaluated. We found that social CPP decreased the percentage of incorrect transitions of grooming and corticosterone to the level of naïve untreated rats. In addition, corticotropin-releasing factor (CRF) was increased in the bed nucleus of stria terminalis after cocaine CPP. In order to study the modulation of social CPP by the CRF system, rats received intracerebroventricular CRF or alpha-helical CRF, a nonselective antagonist of CRF receptors. The subsequent effects on CPP to cocaine or social interaction were observed. CRF injections increased cocaine CPP, whereas alpha-helical CRF injections decreased cocaine CPP. However, alpha-helical CRF injections potentiated social CPP. When social interaction was made available in an alternative context, CRF-induced increase of cocaine preference was reversed completely to the level of rats receiving cocaine paired with alpha-helical CRF. This reversal of cocaine preference was also paralleled by a reversal in CRF-induced increase of p38 MAPK expression in the nucleus accumbens shell. These findings suggest that social interaction could contribute as a valuable component in treatment of substance use disorders by reducing stress levels.

The recognition and management of protracted alcohol withdrawal may improve and modulate the pharmacological treatment of alcohol use disorder

About 50% of persons with an alcohol use disorder may have symptoms of alcohol withdrawal syndrome (AWS) when they reduce or discontinue their alcohol consumption. Protracted alcohol withdrawal (PAW), an underestimated and not yet clearly defined clinical condition that follows the acute stage of AWS, is characterized by the presence of substance-specific signs and symptoms (i.e. anxiety, irritability, mood instability, insomnia, craving) common to acute AWS, but persisting beyond the generally expected acute AWS time frames. Considering that PAW symptoms are mainly related to the neuro-adaptive changes of gamma-aminobutyric acid (GABA) and N-methyl-d-aspartate (NMDA) systems, naltrexone, nalmefene, and disulfiram may not be able to suppress the symptoms of PAW. After treatment of the acute phase of AWS, a more specifically pharmacological therapy able to suppress PAW symptoms could perhaps be used earlier and may be more helpful in preventing the risk of alcohol relapse, which remains higher during the first months of treatment. In light of this, medications acting on GABA and NMDA neurotransmitter systems to counterbalance the up-regulation of NMDA and the down-regulation of GABA could be employed in combination and started as soon as possible.

Association of Prefrontal-Striatal Functional Pathology With Alcohol Abstinence Days at Treatment Initiation and Heavy Drinking After Treatment Initiation

OBJECTIVE

Alcohol use disorder (AUD) is associated with neuroadaptations in brain stress and reward circuits. It is not known whether such neuroadaptations are affected by number of days of alcohol abstinence and whether they influence heavy drinking during the early treatment phase. The authors used a novel functional MRI (fMRI) approach to assess brain responses during sustained exposure to standardized visual stimuli of stressful, alcohol cue, and neutral control images combined with prospective assessment of drinking outcomes during early outpatient treatment, in two related studies.

METHODS

In study 1, 44 treatment-entering patients with AUD and 43 demographically matched healthy control subjects participated in the fMRI experiment to identify dysfunctional responses associated with chronic alcohol abuse. In study 2, 69 treatment-entering patients with AUD were assessed for whether fMRI responses at treatment initiation were influenced by alcohol abstinence and were prospectively predictive of early heavy drinking outcomes.

RESULTS

Relative to control subjects, patients with AUD showed significant hyperreactivity in the ventromedial prefrontal cortex (vmPFC) in response to neutral images, but significant hypoactivation in the vmPFC and ventral striatum in response to stress images and to alcohol cues relative to response to neutral images. In study 2, this specific prefrontal-ventral striatal dysfunction was associated with fewer days of alcohol abstinence and also predicted greater number heavy drinking days during the subsequent 2 weeks of treatment engagement.

CONCLUSIONS

Number of days of alcohol abstinence at treatment initiation significantly affected functional disruption of the prefrontal-striatal responses to stress images and to alcohol cues in patients with AUD, and the severity of this disruption in turn predicted greater heavy drinking during early treatment. Treatments that target this functional prefrontal-striatal pathology could improve early treatment outcomes in AUD.

Blockade of D3 receptor prevents changes in DAT and D3R expression in the mesolimbic dopaminergic circuit produced by social stress- and cocaine prime-induced reinstatement of cocaine-CPP

BACKGROUND

Cocaine may cause persistent changes in the brain, which are more apparent in DA transporter (DAT) and DA receptor availability within the nucleus accumbens (NAc). On the other hand, the DA D3 receptor (D3R) has emerged as a promising pharmacotherapeutic target for substance use disorders.

AIMS

This study aims to assess the impact of selective D3R antagonism on DAT and D3R after reinstatement of cocaine preference (CPP) induced by an acute session of social defeat stress (SDS) and a cocaine prime in mice after a period of abstinence.

METHODS

Male mice were conditioned with 25 mg/kg of cocaine for 4 days. After 60 days of extinction training mice were pretreated with the selective D3R antagonist SB-277011A before the re-exposure to a priming dose of cocaine or to a single SDS session. CPP scores were determined and levels of DAT, D3R, phospho Akt (pAkt) and phospho mTOR (pmTOR) were assessed in the NAc shell.

RESULTS

An increase in DAT and D3R expression was seen in the NAc after both a cocaine prime- and SDS-induced reinstatement of CPP. Pretreatment with SB-277011A blocked elevated DAT and D3R expression as well as SDS-induced reinstatement. By contrast, the blockade of D3R did not modified the cocaine prime-induced CPP. Changes in DAT and D3R expression do not seem to occur via the canonic pathway involving Akt/mTOR.

CONCLUSIONS

Our results suggest that the selective D3R antagonist ability to inhibit DAT and D3R up-regulation could represent a possible mechanism for its behavioral effects in cocaine-memories reinstatement induced by social stress.

Neural mechanisms underlying incubation of methamphetamine craving: A mini-review

Cue-induced drug craving and seeking progressively increases during abstinence. This "incubation of drug craving" phenomenon has been observed in both laboratory animals and humans. Preclinical studies identified several neural mechanisms underlying incubation of drug craving after forced abstinence, primarily focusing on cocaine. Recently, studies started focusing on another powerful psychostimulant, methamphetamine (Meth), and developed new incubation procedures (choice-induced and punishment-induced abstinence). Here, we review mechanistic studies at the circuit, synaptic and molecular levels on incubation of Meth craving. First, we provide an overview of neural adaptations associated with prolonged forced abstinence after extended-access Meth self-administration. Next, we review studies examining the causal roles of discrete brain regions and associated circuits, glutamate transmission, histone deacetylase 5 and oxytocin in incubation of Meth craving after forced abstinence. Lastly, we review causal and correlational studies examining the mechanisms underlying incubation of Meth craving after choice-induced voluntary abstinence and punishment-induced abstinence, respectively. We conclude by discussing the translational potential of these mechanistic studies in Meth relapse prevention in human drug users.

Susceptibility to extinction and reinstatement of ethanol-induced conditioned place preference is related to differences in astrocyte cystine-glutamate antiporter content

Individual susceptibility to alcohol effects plays an important role in the development of alcohol addiction and studies have shown that glutamate release is altered after chronic ethanol consumption. The cystine-glutamate antiporter (xCT) is a protein that regulates glutamate release. However, little is known about the relationship between xCT levels and this individual susceptibility. Thus, this study aimed to evaluate the relationship between the extinction and stress-induced reinstatement of ethanol conditioned place preference (CPP) and xCT levels in the medial prefrontal cortex (mPFC), nucleus accumbens (NAcc) and amygdala (Amy). Male Swiss mice were submitted to a CPP procedure followed by an extinction protocol and then identified as those which extinguished the CPP and those that did not. In another cohort, mice that extinguished the CPP were submitted to a protocol of stress-induced reinstatement. Immediately after the tests, brains were removed for xCT quantification. The xCT levels were significantly lower in the mPFC and NAcc of mice that did not extinguish CPP. Moreover, mice that were susceptible to stress-induced reinstatement of CPP had lower levels of xCT in the NAcc. Our results suggest that individual susceptibility to the extinction and reinstatement of ethanol CPP is related to alterations in xCT levels.

Regulation of Craving and Negative Emotion in Alcohol Use Disorder

BACKGROUND

Alcohol use disorder (AUD) is a chronic, relapsing condition with poor treatment outcomes. Both alcohol craving and negative affect increase alcohol drinking, and-in healthy adults-can be attenuated using cognitive strategies, which rely on the prefrontal cortex (PFC). However, AUD is associated with cognitive impairments and PFC disruptions. Thus, we tested whether individuals with AUD can successfully recruit the PFC to effectively regulate craving and negative emotions, whether neural mechanisms are shared between the two types of regulation, and whether individual differences influence regulation success.

METHODS

During functional magnetic resonance imaging, participants with AUD completed the regulation of craving task (n = 17) that compares a cue-induced craving condition with an instructed regulation condition. They also completed the emotion regulation task (n = 15) that compares a negative affect condition with an instructed regulation condition. Regulation strategies were drawn from cognitive behavioral therapy treatments for AUD. Self-reported craving and negative affect were collected on each trial.

RESULTS

Individuals with AUD effectively regulated their craving and negative affect when instructed to do so using cognitive behavioral therapy-based strategies. Regulation was associated with recruitment of both common and distinct PFC regions across tasks, as well as with reduced activity in regions associated with craving and negative affect (e.g., ventral striatum, amygdala). Effective regulation of craving was associated with negative alcohol expectancies.

CONCLUSIONS

Both common and distinct regulatory systems underlie regulation of craving and negative emotions in AUD, with notable individual differences. This has important implications for AUD treatment.

[Neural circuits and neurotransmitters involved in the effects of psychoactive drugs - State of the art with a focus on cocaine]

Addiction is a chronic disease that has serious consequences, both in terms of public health and economy. Clear characteristics distinguish recreational and controlled use from addiction. Thus, today, addiction includes the notions of compulsive drug use, associated with a loss of control over consumption, leading to craving. When consumption is stopped, withdrawal symptoms may emerge: a negative emotional state, cognitive problems and physical symptoms with some products (alcohol and opiates, for example). Relapse episodes may occur during this withdrawal period, countering the negative effects of withdrawal. Relapse episodes can also be observed after long periods of abstinence. They can be precipitated by re-exposure to the context in which the drugs were taken, or by stress. Regardless of the stage of addiction (e.g., development of the addictive behavior, or relapse) changes in brain function and structure can be observed. Some brain structures are therefore modified, such as the prefrontal cortex, where several neuroadaptations have been identified. Some of these changes are described in this paper.

OREX-1019: A Novel Treatment of Opioid Use Disorder and Relapse Prevention

There is an urgent need for new pharmacological treatments for substance use disorders, including opioid use disorder, particularly for use in relapse prevention. A combination of buprenorphine with naltrexone has shown particular promise, with clinical studies indicating a substantial improvement over treatment with naltrexone alone. OREX-1019 (formerly BU10119) is a compound that mimics the pharmacology of the buprenorphine/naltrexone combination. This study evaluated, in rhesus monkeys, the therapeutic potential of OREX-1019 for treating opioid use disorder. Pretreatment with OREX-1019 (0.01-0.3 mg/kg s.c.) dose-dependently decreased responding for the μ opioid receptor agonist remifentanil in rhesus monkeys but did not maintain levels of responding above vehicle when it was available for self-administration. OREX-1019 (0.01-1.0 mg/kg s.c.) also decreased cue- plus heroin-primed reinstatement of extinguished responding in monkeys that self-administered remifentanil but did not alter cue- plus cocaine-primed reinstatement of responding in monkeys that self-administered cocaine. OREX-1019 (0.3 mg/kg s.c.), like naltrexone (0.1 mg/kg s.c.), increased heart rate and blood pressure, produced overt observable signs, and eliminated food-maintained responding in monkeys treated chronically with morphine. These results confirm that OREX-1019 has little or no efficacy at μ opioid receptorsand has low abuse potential, and, combined with promising safety (clean profile vs. other off-target proteins including the hERG (human ether-a-go-go-related gene) K⁺ channel) and pharmacokinetic data (supporting administration by subcutaneous or sublingual routes, but with low oral bioavailability), suggest it could be a safe and effective alternative to current treatments for opioid use disorders particularly as applied to relapse prevention. SIGNIFICANCE STATEMENT: The novel opioid OREX-1019 potentially provides an improved relapse prevention agent for use in opioid use disorder. The current study demonstrates that in monkeys OREX-1019 is able to inhibit the self-administration of, and cue- plus heroin-primed reinstatement of, responding previously maintained by remifentanil.

The effects of acute stress on consummatory and motivational responses for sucrose in rats after long-term withdrawal from morphine

BACKGROUND

Negative affective states, e.g., anhedonia, may be linked to the long-lasting motivational processes associated with relapse. Here, this study investigated whether, and how, anhedonic states are influenced by stressful events that contribute to craving and relapse.

METHODS

All male rats were pretreated with a binge-like morphine paradigm for five days. After 12 to 16 days of withdrawal, rats were subjected to a one-hour free consumption test or three operant tasks with increasing cost/benefit ratio, i.e., fixed ratio 1 (FR1), progressive ratio (PR), and PR-punishment procedure of reinforcement, with sucrose solutions of three concentrations (4%, 15%, and 60%) as rewards. The consumption and operant responses under FR1 and PR procedures were measured following exposure to acute foot-shock stress (intermittent foot shock, 0.5 mA × 0.5 s × 10 min; mean intershock interval, 40 s), and the operant responses for 60% sucrose solution under PR-punishment procedure was measured following a forced-swim stress (5 minutes).

RESULT

Foot-shock stress increased water consumption in a subpopulation of rats and decreased consumption of sucrose solutions, while it did not influence the operant responses for sucrose solutions under either FR1 or PR procedure. The forced-swim stress reduced operant responses for 60% sucrose solution under PR-punishment procedure, but did not influence responding for 60% sucrose solution under PR procedure. In addition, the forced-swim stress also elevated anxiety level of rats in an open area test.

CONCLUSIONS

Acute stress induced hedonic but not motivational deficit for sucrose reward in protracted drug-abstinent animals. Additional negative emotional states besides anhedonia were evoked by acute stress.

Stress and opioid use disorder: A systematic review

Medication assisted treatment (MAT) is highly effective in reducing illicit opioid use and preventing overdose in individuals with opioid use disorder (OUD); however, treatment retention of patients engaged in MAT is a significant clinical concern. The experience of stress may contribute to a decision to drop out of treatment. The current study is a systematic review conducted across multiple databases of empirical studies on primary appraisal of stress and its relationship to opioid craving, opioid use, and OUD treatment outcomes. Primary appraisal of stress is defined as an explicit inquiry into individual perception of feeling stressed using a self-report measure administered in laboratory, clinical, or naturalistic environment. A total of 21 included studies were organized into three categories: observed stress, experimentally-induced stress, and stress-focused interventions. Appraised stress was generally associated with greater craving, but associations with opioid use and treatment retention were mixed. All but one study included MAT samples and every study sample included some form of drug counseling. These findings suggest that individuals experience considerable stress in spite of receiving standard treatment for OUD. Psychopharmacological interventions targeting stress were promising, but no behavioral interventions specific to stress management were found. The preliminary results with clonidine and lofexidine targeting stress in individuals with OUD warrant further studies. To better understand the impact of stress in OUD, future research should consider using repeated assessment of stress in the context of daily life. Utilization of behavioral treatments specifically targeting stress could have benefits in improving OUD outcomes.

A day-by-day prospective analysis of stress, craving and risk of next day alcohol intake during alcohol use disorder treatment

BACKGROUND

Stress has been known to increase craving in individuals with Alcohol Use Disorders (AUD) and predict future alcohol relapse risk, but whether stress on a particular day affects craving on that day to impact prospective alcohol intake in the real world, particularly during early treatment and recovery, has not been studied thus far.

METHOD

The first study included 85 AUD individuals who reported their daily stress, craving, and alcohol intake in the first two weeks of early treatment. A second validation study included 28 AUD patients monitored daily during eight weeks of outpatient 12-Step based behavioral counseling treatment for AUD. Data were collected from telephone-based daily diaries for 903 days in Study 1 and 1488 in Study 2. Multilevel latent models tested if daily and person-averaged craving mediated the link between stressful events and next day drinking during treatment.

RESULTS

In both Study 1 and 2, exposure to a stressful event on a particular day predicted increased craving on that day (p's≤.002); and such increases in craving predicted the likelihood of drinking the next day (p's≤.014) and the drinking amount (p's< = 008). Individuals who experienced more stressful events reported higher craving (p's≤.012), and higher cravers reported greater next day drinking (p's<.001).

CONCLUSIONS

The results across two studies with separate samples are the first to establish that craving directly mediates the association between stress and next day alcohol intake in individuals with AUD. Findings suggest a need for novel treatment approaches to address stress-induced craving to improve alcohol use outcomes.

Addiction beyond pharmacological effects: The role of environment complexity and bounded rationality

Several decision-making vulnerabilities have been identified as underlying causes for addictive behaviours, or the repeated execution of stereotyped actions despite their adverse consequences. These vulnerabilities are mostly associated with brain alterations caused by the consumption of substances of abuse. However, addiction can also happen in the absence of a pharmacological component, such as seen in pathological gambling and videogaming. We use a new reinforcement learning model to highlight a previously neglected vulnerability that we suggest interacts with those already identified, whilst playing a prominent role in non-pharmacological forms of addiction. Specifically, we show that a dual-learning system (i.e. combining model-based and model-free) can be vulnerable to highly rewarding, but suboptimal actions, that are followed by a complex ramification of stochastic adverse effects. This phenomenon is caused by the overload of the capabilities of an agent, as time and cognitive resources required for exploration, deliberation, situation recognition, and habit formation, all increase as a function of the depth and richness of detail of an environment. Furthermore, the cognitive overload can be aggravated due to alterations (e.g. caused by stress) in the bounded rationality, i.e. the limited amount of resources available for the model-based component, in turn increasing the agent's chances to develop or maintain addictive behaviours. Our study demonstrates that, independent of drug consumption, addictive behaviours can arise in the interaction between the environmental complexity and the biologically finite resources available to explore and represent it.

Cholinergic Receptor Blockade in the VTA Attenuates Cue-Induced Cocaine-Seeking and Reverses the Anxiogenic Effects of Forced Abstinence

Drug relapse after periods of abstinence is a common feature of substance abuse. Moreover, anxiety and other mood disorders are often co-morbid with substance abuse. Cholinergic receptors in the ventral tegmental area (VTA) are known to mediate drug-seeking and anxiety-related behavior in rodent models. However, it is unclear if overlapping VTA cholinergic mechanisms mediate drug relapse and anxiety-related behaviors associated with drug abstinence. We examined the effects of VTA cholinergic receptor blockade on cue-induced cocaine seeking and anxiety during cocaine abstinence. Male Sprague-Dawley rats were trained to self-administer intravenous cocaine (~0.5 mg/kg/infusion, FR1 schedule) for 10 days, followed by 14 days of forced abstinence. VTA infusion of the non-selective nicotinic acetylcholine receptor antagonist mecamylamine (0, 10, and 30 μg/side) or the non-selective muscarinic receptor antagonist scopolamine (0, 2.4 and 24 μg /side) significantly decreased cue-induced cocaine seeking. In cocaine naïve rats, VTA mecamylamine or scopolamine also led to dose-dependent increases in open arm time in the elevated plus maze (EPM). In contrast, rats that received I.V. cocaine, compared to received I.V. saline rats, displayed an anxiogenic response on day 14 of abstinence as reflected by decreased open arm time in the EPM. Furthermore, low doses of VTA mecamylamine (10 μg /side) or scopolamine (2.4 μg /side), that did not alter EPM behavior in cocaine naive rats, were sufficient to reverse the anxiogenic effects of cocaine abstinence. Together, these data point to an overlapping role of VTA cholinergic mechanisms to regulate relapse and mood disorder-related responses during cocaine abstinence.

Individual Vulnerability to Stress Is Associated With Increased Demand for Intravenous Heroin Self-administration in Rats

Opioid use is a widespread epidemic, and traumatic stress exposure is a critical risk factor in opioid use and relapse. There is a significant gap in our understanding of how stress contributes to heroin use, and there are limited studies investigating individual differences underlying stress reactivity and subsequent stress-induced heroin self-administration. We hypothesized that greater individual vulnerability to stress would predict higher demand for heroin self-administration in a within-subjects rodent model of stress and heroin use comorbidity. Male rats were exposed to inescapable intermittent swim stress (ISS) and individual biological (corticosterone) or behavioral [open field, social exploration, and forced swim tests (FSTs)] measures were assessed before and after the stress episode. Individual demand for self-administered heroin (0.05 mg/kg/infusion; 12-h sessions) was assessed using a behavioral economics approach followed by extinction and reinstatement tests triggered by stress re-exposure, non-contingent cue presentations, and yohimbine (0, 1.0, or 2.5 mg/kg). We found that behavioral, biological, and a combination of behavioral and biological markers sampled prior to and after the stress episode that occurred weeks before the access to heroin self-administration predicted the magnitude of individual demand for heroin. Non-contingent presentation of cues, that were previously associated with heroin, reinstated heroin seeking in extinction. For the first time, we show that individual biological response to an ecologically relevant stressor in combination with associated behavioral markers can be used to predict subsequent economic demand for heroin.