A systems medicine research approach for studying alcohol addiction

The ReCoDe addiction research consortium: Losing and regaining control over drug intake-Findings and future perspectives

Substance use disorders (SUDs) are seen as a continuum ranging from goal-directed and hedonic drug use to loss of control over drug intake with aversive consequences for mental and physical health and social functioning. The main goals of our interdisciplinary German collaborative research centre on Losing and Regaining Control over Drug Intake (ReCoDe) are (i) to study triggers (drug cues, stressors, drug priming) and modifying factors (age, gender, physical activity, cognitive functions, childhood adversity, social factors, such as loneliness and social contact/interaction) that longitudinally modulate the trajectories of losing and regaining control over drug consumption under real-life conditions. (ii) To study underlying behavioural, cognitive and neurobiological mechanisms of disease trajectories and drug-related behaviours and (iii) to provide non-invasive mechanism-based interventions. These goals are achieved by: (A) using innovative mHealth (mobile health) tools to longitudinally monitor the effects of triggers and modifying factors on drug consumption patterns in real life in a cohort of 900 patients with alcohol use disorder. This approach will be complemented by animal models of addiction with 24/7 automated behavioural monitoring across an entire disease trajectory; i.e. from a naïve state to a drug-taking state to an addiction or resilience-like state. (B) The identification and, if applicable, computational modelling of key molecular, neurobiological and psychological mechanisms (e.g., reduced cognitive flexibility) mediating the effects of such triggers and modifying factors on disease trajectories. (C) Developing and testing non-invasive interventions (e.g., Just-In-Time-Adaptive-Interventions (JITAIs), various non-invasive brain stimulations (NIBS), individualized physical activity) that specifically target the underlying mechanisms for regaining control over drug intake. Here, we will report on the most important results of the first funding period and outline our future research strategy.

Alcohol Drinking Patterns and Laboratory Indices of Health: Does Type of Alcohol Preferred Make a Difference?

Although excessive alcohol consumption is a highly prevalent public health problem the data on the associations between alcohol consumption and health outcomes in individuals preferring different types of alcoholic beverages has remained unclear. We examined the relationships between the amounts and patterns of drinking with the data on laboratory indices of liver function, lipid status and inflammation in a national population-based health survey (FINRISK). Data on health status, alcohol drinking, types of alcoholic beverages preferred, body weight, smoking, coffee consumption and physical activity were recorded from 22,432 subjects (10,626 men, 11,806 women), age range 25-74 years. The participants were divided to subgroups based on the amounts of regular alcohol intake (abstainers, moderate and heavy drinkers), patterns of drinking (binge or regular) and the type of alcoholic beverage preferred (wine, beer, cider or long drink, hard liquor or mixed). Regular drinking was found to be more typical in wine drinkers whereas the subjects preferring beer or hard liquor were more often binge-type drinkers and cigarette smokers. Alcohol use in all forms was associated with increased frequencies of abnormalities in the markers of liver function, lipid status and inflammation even at rather low levels of consumption. The highest rates of abnormalities occurred, however, in the subgroups of binge-type drinkers preferring beer or hard liquor. These results demonstrate that adverse consequences of alcohol occur even at moderate average drinking levels especially in individuals who engage in binge drinking and in those preferring beer or hard liquor. Further emphasis should be placed on such patterns of drinking in policies aimed at preventing alcohol-induced adverse health outcomes.

mGlu2 mechanism-based interventions to treat alcohol relapse

Recently we identified a deficiency in metabotropic glutamate receptor 2 (mGlu2) function in the corticoaccumbal pathway, as a common pathological mechanism underlying alcohol-seeking and relapse behavior. Based on this mechanism, we hypothesized that mGlu2/3 agonists and mGlu2 positive allosteric modulators (PAMs) may be effective in reducing relapse-like behavior. Two mGlu2/3 agonists, LY379268 and LY354740 (a structural analog of LY379268 six-fold more potent in activating mGlu2 over mGluR3), were tested in a well-established rat model of relapse, the alcohol deprivation effect (ADE) with repeated deprivation phases. Since these agonists do not readily discriminate between contributions of mGlu2 and mGluR3, we also tested LY487379, a highly specific PAM that potentiates the effect of glutamate on the mGlu2 with less specificity on other mGlu receptor subtypes. Both LY379268 and LY354740 significantly and dose-dependently reduced the expression of the ADE. No significant changes in water intake, body weight and locomotor activity were observed. Importantly, repeated administration of mGlu2/3 agonist did not lead to tolerance development. mGlu2 PAM LY487379 treatment significantly reduced expression of the ADE in both male and female rats. Combination treatment of mGlu2/3 agonist and PAM had similar effect on relapse-like drinking to that seen in mGlu2/3 agonist treatment alone. Together with other preclinical data showing that PAMs can reduce alcohol-seeking behavior we conclude that mGlu2 PAMs should be considered for clinical trials in alcohol-dependent patients.

Reward drinking and naltrexone treatment response among young adult heavy drinkers

AIMS

Theory-driven, exploratory study to: (i) identify a reward drinking phenotype in young adults; (ii) evaluate this phenotype as a predictor of naltrexone response; and (iii) examine mechanisms of naltrexone in reward drinkers.

DESIGN

Secondary analysis of a randomized controlled trial.

SETTING

USA.

PARTICIPANTS

A total of 128 young adult (ages 18-25) heavy drinkers.

INTERVENTIONS

Naltrexone versus placebo.

MEASUREMENTS

Daily surveys assessed affect, urge, drinking, and context. The Drinking Motives Questionnaire was used to identify phenotypes based on reward (enhancement motives) and relief (coping motives) drinking.

FINDINGS

We identified three profiles: "Low reward/Low relief" (14.1%; low enhancement/low coping motives); "Reward drinkers" (62.2%; high enhancement/low coping motives); and "High reward/High relief" (22.7%; high enhancement/high coping motives). Among reward drinkers (versus low profile), naltrexone significantly reduced percent days drinking to intoxication (blood alcohol concentration [BAC] ≥0.08) (PDI) (d = 0.56; 95% CI [0.17, 0.96]) and percent high intensity drinking days (PHID) (8/10 drinks for women/men) (d = 0.32; 95% CI [0.01, 0.68]). Among the high reward/high relief profile drinkers (versus low profile), naltrexone reduced PHID (d = 0.69; 95% CI [0.02, 1.50]). Using profile-informed cutoffs and observed scores (for clinical applicability): (i) among cutoff-derived reward drinkers, we found a medium-to-large (d = 0.66; 95% CI [0.24, 1.16]) and small effect (d = 0.28; 95% CI [0.04, 0.72]) of naltrexone in reducing PDI and PHID, respectively; and (ii) among the cutoff-derived high reward/high relief subgroup, we found a medium-to-large effect (d = 0.63; 95% CI [0.05, 1.1]) of naltrexone in reducing PHID. Among reward drinkers (not other profiles), naltrexone reduced drinking on days a drinking event occurred by weakening the within-day association between positive affect and urges (P < 0.05).

CONCLUSIONS

Naltrexone has pronounced effects in reducing risky drinking among young adult reward drinkers (high reward/low relief) by reducing urges on days when individuals have higher positive affect and are exposed to a drinking event. Naltrexone also appears to reduce risky drinking among young adult high reward/high relief drinkers, but not via the same mechanism.

Oxytocin attenuates neural response to emotional faces in social drinkers: an fMRI study

INTRODUCTION

Oxytocin is a key mediator of emotional and social behavior that seems to be of relevance for the development and maintenance of addictive behaviors. We thus investigated the effect of oxytocin on neural response and behavior during a face-matching task in a sample of social drinkers.

METHODS

Thirteen social drinkers underwent a randomized double-blind placebo-controlled cross-over functional magnetic resonance imaging face-matching task with and without prior intranasal application of 24 international units oxytocin. Effects of oxytocin and task condition (faces, shapes) on brain activation and individual task performance were assessed.

RESULTS

Face-matching compared to shape-matching trials resulted in higher brain activation in the bilateral amygdala, hippocampus and parts of the occipital gyri. Oxytocin application vs. placebo reduced activation in bilateral amygdala, parts of the frontal gyri, and the parietal lobe. Region of interest analyses indicated that the oxytocin-induced attenuation of amygdala response was specific to face-stimuli and associated with lower subjective alcohol craving, and a lower percentage of heavy-drinking days (defined as ≥ 5 standard drinks/day).

CONCLUSION

For the first time, we could show that a larger oxytocin-induced attenuation of amygdala response to fearful faces is associated with lower subjective craving for alcohol and percentage of heavy drinking days in social drinkers. Modulation of amygdala activation, induced by emotional stimuli, might represent a neurobiological substrate of oxytocin's protective effects on drug seeking behavior.

Acute alcohol withdrawal and recovery in men lead to profound changes in DNA methylation profiles: a longitudinal clinical study

BACKGROUND AND AIMS

Withdrawal is a serious and sometimes life-threatening event in alcohol-dependent individuals. It has been suggested that epigenetic processes may play a role in this context. This study aimed to identify genes and pathways involved in such processes which hint to relevant mechanisms underlying withdrawal.

DESIGN

Cross-sectional case-control study and longitudinal within-cases study during alcohol withdrawal and after 2 weeks of recovery SETTING: Addiction medicine departments in two university hospitals in southern Germany.

PARTICIPANTS/CASES

Ninety-nine alcohol-dependent male patients receiving in-patient treatment and suffering from severe withdrawal symptoms during detoxification and 95 age-matched male controls.

MEASUREMENTS

Epigenome-wide methylation patterns were analyzed in patients during acute alcohol withdrawal and after 2 weeks of recovery, as well as in age-matched controls using Illumina EPIC bead chips. Methylation levels of patients and controls were tested for association with withdrawal status. Tests were adjusted for technical and batch effects, age, smoking and cell type distribution. Single-site analysis, as well as an analysis of differentially methylated regions and gene ontology analysis, were performed.

FINDINGS

We found pronounced epigenome-wide significant [false discovery rate (FDR) < 0.05] differences between patients during withdrawal and after 2 weeks [2876 cytosine-phosphate-guanine (CpG) sites], as well as between patients and controls (9845 and 6094 CpG sites comparing patients at time-point 1 and patients at time-point 2 versus controls, respectively). Analysis of differentially methylated regions and involved pathways revealed an over-representation of gene ontology terms related to the immune system response. Differences between patients and controls diminished after recovery (> 800 CpG sites less), suggesting a partial reversibility of alcohol- and withdrawal-related methylation.

CONCLUSIONS

Acute alcohol withdrawal in severely dependent male patients appears to be associated with extensive changes in epigenome-wide methylation patterns. In particular, genes involved in immune system response seem to be affected by this condition.

Endocannabinoid LTD in Accumbal D1 Neurons Mediates Reward-Seeking Behavior

The nucleus accumbens (NAc) plays a key role in drug-related behavior and natural reward learning. Synaptic plasticity in dopamine D1 and D2 receptor medium spiny neurons (MSNs) of the NAc and the endogenous cannabinoid (eCB) system have been implicated in reward seeking. However, the precise molecular and physiological basis of reward-seeking behavior remains unknown. We found that the specific deletion of metabotropic glutamate receptor 5 (mGluR5) in D1-expressing MSNs (D1^miRmGluR5 mice) abolishes eCB-mediated long-term depression (LTD) and prevents the expression of drug (cocaine and ethanol), natural reward (saccharin), and brain-stimulation-seeking behavior. In vivo enhancement of 2-arachidonoylglycerol (2-AG) eCB signaling within the NAc core restores both eCB-LTD and reward-seeking behavior in D1^miRmGluR5 mice. The data suggest a model where the eCB and glutamatergic systems of the NAc act in concert to mediate reward-seeking responses.

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mGluR5-D1-CB1-induced eCB-LTD mediates drugs of abuse and natural reward seeking

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eCB-LTD in D2-MSNs plays no important role in processing of reward-seeking responses

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Loss of eCB-LTD is a consequence of higher MAGL activity and lower CB1R expression

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Acute drug administration stops craving for alternative rewards on following days

Volumetric Prefrontal Cortex Alterations in Patients With Alcohol Dependence and the Involvement of Self-Control

Background:

Aspects of self-control such as sensation seeking and impaired impulse control have been implicated in alcohol dependence (ALC). Conversely, sensation seeking has been ascribed a possible protective role in stress-related psychopathologies. We therefore examined gray matter (GM) morphology in individuals with ALC, focusing on differences in prefrontal regions that have been associated with self-control. Additionally, we accounted for differences in lifetime alcohol intake regarding self-control measures and cortical structures in ALC patients.

Methods:

With voxel-based morphometry (VBM) focusing on prefrontal a priori defined regions of interest, we assessed a group of 62 detoxified ALC patients and 62 healthy controls (HC). ALC patients were subsequently divided into high (n = 9) and low consumers (n = 53). Self-control was assessed by use of the Barratt Impulsiveness Scale and the Sensation Seeking Scale.

Results:

Compared to HC, ALC had significantly less GM volume in bilateral middle frontal gyrus (MFG) and right medial prefrontal cortex as well as in the right anterior cingulate. High-consuming ALC showed smaller GM in right orbitofrontal cortex as well as lower sensation seeking scores than low consumers. In low-consuming ALC, right MFG-GM was positively associated with magnitude of sensation seeking; particularly, larger MFG-GM correlated with greater thrill and adventure seeking.

Conclusion:

Thus, our findings (i) indicate deficient GM volume in prefrontal areas related to self-control and (ii) might accentuate the phenotypic divergence of ALC patients and emphasize the importance of the development of individual treatment options.

Advancing Precision Medicine for Alcohol Use Disorder: Replication and Extension of Reward Drinking as a Predictor of Naltrexone Response

Background

Precision medicine aims to identify those patients who will benefit the most from specific treatments. Recent work found large effects of naltrexone among “reward drinkers,” defined as individuals who drink primarily for the rewarding effects of alcohol. This study sought to replicate and extend these recent findings by examining whether the desire to drink mediated the effect of naltrexone among reward drinkers.

Methods

We conducted a secondary analysis of a 12‐week randomized clinical trial of daily or targeted naltrexone among problem drinkers (n = 163), with a focus on 86 individuals (n = 45 naltrexone and n = 41 placebo) who received daily medication. Interactive voice response technology was used to collect daily reports of drinking and desire to drink. Factor mixture models were used to derive reward and relief phenotypes. Moderation analyses were used to evaluate naltrexone effects, with phenotype as a moderator variable. Multilevel mediation tested average desire to drink as a mediator.

Results

Results indicated 4 phenotypes: low reward/low relief; low reward/high relief; high reward/low relief; and high reward/high relief. There was an interaction between the high reward/low relief subgroup (n = 10) and daily naltrexone versus placebo on drinks per drinking day (DPDD; p = 0.03), percent heavy drinking days (p = 0.004), and daily drinking (p = 0.02). As compared to placebo, individuals in the high reward/low relief phenotype who received daily naltrexone had significantly fewer DPDD (Cohen's d = 2.05) and had a lower proportion of heavy drinking days (Cohen's d = 1.75). As hypothesized, reductions in average desire to drink mediated the effect of naltrexone on average daily drinking among the high reward/low relief drinkers (moderated mediation effect: p = 0.029).

Conclusions

This theory‐driven study replicates the empirical finding that naltrexone is particularly efficacious among high reward/low relief drinkers. Our study brings the field a step closer to the potential of using a precision medicine approach to treating alcohol use disorder.

Refined parcellation of the nervous system by algorithmic detection of hidden features within communities

The nervous system can be represented as a multiscale network comprised by single cells or ensembles that are linked by physical or functional connections. Groups of morphologically and physiologically diverse neurons are wired as connectivity patterns with a certain degree of universality across species and individual variability. Thereby, community detection approaches are often used to characterize how neural units cluster into such densely interconnected groups. However, the communities may possess deeper structural features that remain undetected by current algorithms. We present a scheme for refined parcellation of neuronal networks, by identifying local integrator units (LU) that are contained in network communities. An LU is defined as a connected subnetwork in which all neuronal connections are constrained within this unit, and can be formed for instance by a set of interneurons. Our method uses the Louvain algorithm to detect communities and participation coefficients to discriminate local neurons from global hubs. The sensitivity of the algorithm for discovering LUs with respect to the choice of community detection algorithm and network parameters was tested by simulations of different synthetic networks. The appropriateness of the algorithm for real-world scenarios was demonstrated on weighted and binary Caenorhabditis elegans connectomes. The detected LUs are distinctly localized within the worm body and clearly define functional groups. This approach provides a robust, observer-independent parcellation strategy that is useful for functional structure confirmation and potentially contributes to the current efforts in quantitative whole-brain architectonics of different species as well as the analysis of functional connectivity networks.

Liver enzymes in alcohol consumers with or without binge drinking

BACKGROUND

While alcohol use is linked with a wide variety of health problems, the question of whether differences in drinking patterns could yield different outcomes has remained unclear.

PATIENTS AND METHODS

We measured liver enzymes (ALT, GGT) from alcohol consumers with or without binge drinking from a population-based sample in Finland, where binge-type drinking is common. Data on alcohol use, diet, body weight, lifestyle (smoking, coffee consumption, physical activity), and health status were collected from 19225 subjects (9492 men, 9733 women), aged 25-74 years. The participants were subsequently classified to subgroups, both according to the frequencies of binge drinking and the amounts of regular alcohol intake (low-, medium-, and high-risk drinking).

RESULTS

The quantity of regular alcohol use was roughly linearly related with GGT and ALT activities. ANOVA analyses of the trends according to the frequency of binge drinking showed a significant GGT increase in both men (p < 0.0005) and women (p < 0.0005), and a significant increase of ALT in men (p < 0.0005). In those with low-risk overall consumption, markedly higher GGT (p < 0.0005) and ALT (p < 0.0005) occurred in those with binge drinking more than once a month, compared with those with no such occasions. Binge drinking occurring ≤1/month also resulted in higher GGT (p < 0.0005) and ALT (p < 0.05) activities.

CONCLUSIONS

These results emphasize possible adverse consequences of binge drinking on hepatic function even in those with low-risk overall consumption. The pattern of drinking should be more systematically implicated in clinical recommendations for drinking reduction.

Risk profiles for heavy drinking in adolescence: differential effects of gender

Abnormalities across different domains of neuropsychological functioning may constitute a risk factor for heavy drinking during adolescence and for developing alcohol use disorders later in life. However, the exact nature of such multi-domain risk profiles is unclear, and it is further unclear whether these risk profiles differ between genders. We combined longitudinal and cross-sectional analyses on the large IMAGEN sample (N ≈ 1000) to predict heavy drinking at age 19 from gray matter volume as well as from psychosocial data at age 14 and 19-for males and females separately. Heavy drinking was associated with reduced gray matter volume in 19-year-olds' bilateral ACC, MPFC, thalamus, middle, medial and superior OFC as well as left amygdala and anterior insula and right inferior OFC. Notably, this lower gray matter volume associated with heavy drinking was stronger in females than in males. In both genders, we observed that impulsivity and facets of novelty seeking at the age of 14 and 19, as well as hopelessness at the age of 14, are risk factors for heavy drinking at the age of 19. Stressful life events with internal (but not external) locus of control were associated with heavy drinking only at age 19. Personality and stress assessment in adolescents may help to better target counseling and prevention programs. This might reduce heavy drinking in adolescents and hence reduce the risk of early brain atrophy, especially in females. In turn, this could additionally reduce the risk of developing alcohol use disorders later in adulthood.

Pavlovian to Instrumental Transfer Responses Do Not Correlate With Addiction-Like Behavior in Rats

Pavlovian learning plays a prominent role in the etiology of addiction. The influence of Pavlovian conditioning on the expression of an instrumental response can be studied using the Pavlovian-to-instrumental transfer (PIT) paradigm. This paradigm consists of independent Pavlovian conditioning and instrumental training prior to the combination of both during the test. During this test, the reward is not available, and an increase in the instrumental responding during conditioned stimuli presentation is a measure of PIT. Recent studies have reported a higher PIT in alcohol and nicotine dependent patients, suggesting that enhanced PIT might be a marker for dependence vulnerability. However, these studies did not use standard PIT procedures, and a clear correlation between an enhanced PIT and drug-related and addictive behaviors has so far not been demonstrated. For a systematic evaluation rats were trained in a cocaine addiction model. Addicted-like and non-addicted-like rats were subsequently assessed in the PIT paradigm. In a further experiment, rats were first tested in the PIT paradigm and thereafter subjected to cocaine self-administration (CSA) training. Our results revealed that addicted-like rats did not differ from non-addicted-like in their performance in the PIT test. However, CSA behavior showed a positive correlation with PIT. This data suggests that stronger PIT may predict higher motivational impact of conditioned stimuli on drug self-administration and improved learning of drug-cue association rather than the risk to develop addiction as such.

Drinking Levels and Profiles of Alcohol Addicted Rats Predict Response to Nalmefene

Background: Pharmacotherapeutic options supporting the treatment of alcohol dependence are recommended and available but underutilized, partly due to questions about efficacy. Nalmefene, a μ-opioid receptor antagonist and partial kappa receptor agonist, is recommended for reduction of alcohol consumption, but evidence about its effectiveness has been equivocal; identifying factors which predict response will help optimize treatment.

Methods: The alcohol deprivation effect paradigm is a tightly controlled procedure comprising repeated deprivation and reintroduction phases, leading to increased preference for alcohol; reintroduction approximates relapse. Using a digital drinkometer system measuring high-resolution drinking behavior, we examined the effects of nalmefene on relapse drinking behavior in alcohol addicted rats. We also tested whether drinking behavior in the relapse phase prior to nalmefene administration predicted treatment response. We further examined whether longitudinal drinking behavior and locomotor activity predicted treatment response.

Results: Our results showed that nalmefene (0.3 mg/kg) reduced relapse-like consumption significantly (∼20%) compared to vehicle on the first 2 days of alcohol reintroduction. Examining the first 6 h of a preceded treatment-free relapse episode revealed drinking patterns clustering the rats into responders (reduction of >40%, n = 17) and non-responders (reduction of <40%, n = 7) to subsequent nalmefene treatment. During the first 6 h of the preceding relapse phase, responders consumed more alcohol than non-responders; the amount of alcohol consumed during each drinking approach was larger but frequency of drinking did not differ. Longitudinal drinking behavior and locomotor activity did not significantly predict response.

Conclusion: Our results suggest that nalmefene reduces alcohol intake during a relapse-like situation but effectiveness can differ greatly at the individual level. However, who responds may be informed by examining drinking profiles and rats that show high drinking levels prior to treatment are more likely to respond to nalmefene.

Quantitative evaluation of cue-induced reinstatement model for evidence-based experimental optimization

Cue-induced reinstatement is a widely used model for investigating relapse of reward-seeking behavior with high face validity in relation to clinical observations. Yet, face validity is not sufficient to evaluate an animal model, and quantitative, evidence-based analysis is required to estimate the ultimate applicability of this paradigm. Furthermore, such analysis would allow an accurate and reproducible design of future experiments. Here, we conducted meta-analysis and cluster analysis to characterize the impact of cue type (visual, auditory, olfactory or combinations thereof), intensity (e.g. light frequency, sound volume and odor concentration), reward type (e.g. different drugs of abuse, sucrose and food pellets) and model parameters (e.g. housing condition, age, gender and strain of animals) on reinstatement levels. We selected 184 publications for meta-analysis based on inclusion criteria with a total number of 3889 rats. Our analysis suggested that the exact level of reinstatement depends on neither cue type, nor intensity nor on the type of reward. While all cues induced reinstatement to reward-seeking behavior, it is the model parameters, in particular, the housing conditions, age and strain, that defined the final reinstatement levels. In particular, single-housed, adolescent, Wistar or Lister Hooded rats showed significantly higher reinstatement than adult, Sparague-Dawley rats housed in groups. Our findings suggest that model parameters (for example, single housing) evoke stress-induced behaviors that affect reinstatement more than cue/reward factors.

Imaging resilience and recovery in alcohol dependence

BACKGROUND AND AIMS

Resilience and recovery are of increasing importance in the field of alcohol dependence (AD). This paper describes how imaging studies in man can be used to assess the neurobiological correlates of resilience and, if longitudinal, of disease trajectories, progression rates and markers for recovery to inform treatment and prevention options.

METHODS

Original papers on recovery and resilience in alcohol addiction and its neurobiological correlates were identified from PubMed and have been analyzed and condensed within a systematic literature review.

RESULTS

Findings deriving from functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies have identified links between increased resilience and less task-elicited neural activation within the basal ganglia, and benefits of heightened neural pre-frontal cortex (PFC) engagement regarding resilience in a broader sense; namely, resilience against relapse in early abstinence of AD. Furthermore, findings consistently propose at least partial recovery of brain glucose metabolism and executive and general cognitive functioning, as well as structural plasticity effects throughout the brain of alcohol-dependent patients during the course of short-, medium- and long-term abstinence, even when patients only lowered their alcohol consumption to a moderate level. Additionally, specific factors were found that appear to influence these observed brain recovery processes in AD, e.g. genotype-dependent neuronal (re)growth, gender-specific neural recovery effects, critical interfering effects of psychiatric comorbidities, additional smoking or marijuana influences or adolescent alcohol abuse.

CONCLUSIONS

Neuroimaging research has uncovered neurobiological markers that appear to be linked to resilience and improved recovery capacities that are furthermore influenced by various factors such as gender or genetics. Consequently, future system-oriented approaches may help to establish a broad neuroscience-based research framework for alcohol dependence.

Basal glucocorticoid receptor activation induces proliferation and inhibits neuronal differentiation of human induced pluripotent stem cell-derived neuronal precursor cells

Glucocorticoids (GC) have first been shown to originate from the adrenal glands where synthesis and release is controlled by the hypothalamic-pituitary-adrenal (HPA) axis. Recently, it was shown that GC and other steroid hormones are also synthesized in the central nervous system, so-called neurosteroids. GC bind to specific GC receptors (GR) which function as ligand-activated transcription factors. GR are expressed in nearly all cell types in the brain, and therefore GC have a strong impact on neuronal development. Most knowledge of the influence of GC on neurodevelopment has been obtained from animal research. Recent advances in stem cell technology made it possible to generate neuronal precursor cells (NPCs) and neurons from human induced pluripotent stem cells (hiPSCs). To explore the cellular mechanism of GC affecting human neuronal development, we quantified the proliferation and differentiation of hiPSCs-derived NPCs in the absence and presence of the selective high-affinity GR agonist dexamethasone and the selective GR antagonist mifepristone, respectively. Our results show that inhibition of GR significantly reduced proliferation of NPCs and promoted differentiation whereas GR activation suppressed neuronal differentiation. This implies that neuronal GC must be present in NPCs for proliferation. Consequently we identified the presence of 11-β-hydroxylase CYP11B1, which hydroxylates the respective steroid precursors to bioactive GC, in NPCs. We propose that hiPSC technology offers an ideal system to get more insight into the synthesising and regulatory pathways in steroidogenesis in human neurons and to differentiate between the mechanism by which adrenal GC and neuronal GC impact on neurodevelopment.

Efficacy and side effects of baclofen and the novel GABAB receptor positive allosteric modulator CMPPE in animal models for alcohol and cocaine addiction

RATIONALE

Preclinical studies suggest that the GABA_B receptor is a potential target for treatment of substance use disorders. However, recent clinical trials report adverse effects in patients treated with the GABA_B receptor agonist baclofen and even question efficacy. How can the discrepancy between preclinical and clinical findings be explained?

OBJECTIVE

To test efficacy and adverse effects of baclofen and the novel GABA_B positive allosteric modulator (PAM) CMPPE in rat addiction models, which were developed in accordance with DSM.

METHODS

We used a well-characterized rat model of long-term alcohol consumption with repeated deprivation phases that result in compulsive alcohol drinking in a relapse situation, and a rat model of long-term intravenous cocaine self-administration resulting in key symptoms of addictive behavior. We tested repeated baclofen (0, 1, and 3 mg/kg; i.p.) and CMPPE doses (0, 10, and 30 mg/kg; i.p.) in relapse-like situations, in either alcohol or cocaine addicted-like rats.

RESULTS

Baclofen produced a weak anti-relapse effect at the highest dose in alcohol addicted-like rats, and this effect was mainly due to the treatment-induced sedation. CMPPE had a better profile, with a dose-dependent reduction of relapse-like alcohol drinking and without any signs of sedation. The cue-induced cocaine-seeking response was completely abolished by both compounds.

CONCLUSION

Positive allosteric modulation of the GABA_B receptor provides efficacy, and no observable side effects in relapse behavior whereas baclofen may cause, not only sedation, but also considerable impairment of food intake or metabolism. However, targeting GABA_B receptors may be effective in reducing certain aspects of addictive-like behavior, such as cue-reactivity.

Targeted overexpression of CRH receptor subtype 1 in central amygdala neurons: effect on alcohol-seeking behavior

RATIONALE

The corticotropin-releasing hormone (CRH) system is a key mediator of stress-induced responses in alcohol-seeking behavior. Recent research has identified the central nucleus of the amygdala (CeA), a brain region involved in the regulation of fear and stress-induced responses that is especially rich in CRH-positive neurons, as a key player in mediating excessive alcohol seeking. However, detailed characterization of the specific influences that local neuronal populations exert in mediating alcohol responses is hampered by current limitations in pharmacological and immunohistochemical tools for targeting CRH receptor subtype 1 (CRHR1).

OBJECTIVE

In this study, we investigated the effect of cell- and region-specific overexpression of CRHR1 in the CeA using a novel transgenic tool.

METHODS

Co-expression of CRHR1 in calcium-calmodulin-dependent kinase II (αCaMKII) neurons of the amygdala was demonstrated by double immunohistochemistry using a Crhr1-GFP reporter mouse line. A Cre-inducible Crhr1-expressing adeno-associated virus (AAV) was site-specifically injected into the CeA of αCaMKII-Cre^ERT2 transgenic rats to analyze the role of CRHR1 in αCaMKII neurons on alcohol self-administration and reinstatement behavior.

RESULTS

Forty-eight percent of CRHR1-containing cells showed co-expression of αCaMKII in the CeA. AAV-mediated gene transfer in αCaMKII neurons induced a 24-fold increase of Crhr1 mRNA in the CeA which had no effect on locomotor activity, alcohol self-administration, or cue-induced reinstatement. However, rats overexpressing Crhr1 in the CeA increased responding in the stress-induced reinstatement task with yohimbine serving as a pharmacological stressor.

CONCLUSION

We demonstrate that CRHR1 overexpression in CeA-αCaMKII neurons is sufficient to mediate increased vulnerability to stress-triggered relapse into alcohol seeking.

Oxytocin Reduces Alcohol Cue-Reactivity in Alcohol-Dependent Rats and Humans

Approved pharmacological treatments for alcohol use disorder are limited in their effectiveness, and new drugs that can easily be translated into the clinic are warranted. One of those candidates is oxytocin because of its interaction with several alcohol-induced effects. Alcohol-dependent rats as well as post-mortem brains of human alcoholics and controls were analyzed for the expression of the oxytocin system by qRT-PCR, in situ hybridization, receptor autoradiography ([¹²⁵I]OVTA binding), and immunohistochemistry. Alcohol self-administration and cue-induced reinstatement behavior was measured after intracerebroventricular injection of 10 nM oxytocin in dependent rats. Here we show a pronounced upregulation of oxytocin receptors in brain tissues of alcohol-dependent rats and deceased alcoholics, primarily in frontal and striatal areas. This upregulation stems most likely from reduced oxytocin expression in hypothalamic nuclei. Pharmacological validation showed that oxytocin reduced cue-induced reinstatement response in dependent rats-an effect that was not observed in non-dependent rats. Finally, a clinical pilot study (German clinical trial number DRKS00009253) using functional magnetic resonance imaging in heavy social male drinkers showed that intranasal oxytocin (24 IU) decreased neural cue-reactivity in brain networks similar to those detected in dependent rats and humans with increased oxytocin receptor expression. These studies suggest that oxytocin might be used as an anticraving medication and thus may positively affect treatment outcomes in alcoholics.

Targeting Glycine Reuptake in Alcohol Seeking and Relapse

It has recently been demonstrated that pharmacological blockade of the glycine transporter 1 (GlyT1) reduced alcohol intake and relapse in rats. The aim of the present study was to further explore the role of GlyT1 in alcohol relapse-like behavior. For this purpose we used three different GlyT1 blockers-SSR504734, A-1246399, and RO4993850-and tested their effect on alcohol-seeking and relapse-like consumption. Two behavioral models, the alcohol deprivation effect model and the cue-induced reinstatement model, were used. Our data show that all three GlyT1 blockers reduce relapse-like alcohol consumption and cause either minimal or no side effects, measured as changes in home-cage activity, water intake, and body weight. In the reinstatement test, GlyT1 blockers completely abolished alcohol-seeking responses. Furthermore, we tested other drug/cue associations and found that cocaine-seeking responses were also abolished by GlyT1 blockade. Our data confirm that GlyT1 can be used as a target to develop novel anticraving and antirelapse drugs.

Precision Medicine in Alcohol Dependence: A Controlled Trial Testing Pharmacotherapy Response Among Reward and Relief Drinking Phenotypes

Randomized trials of medications for alcohol dependence (AD) often report no differences between active medications. Few studies in AD have tested hypotheses regarding which medication will work best for which patients (ie, precision medicine). The PREDICT study tested acamprosate and naltrexone vs placebo in 426 randomly assigned AD patients in a 3-month treatment. PREDICT proposed individuals whose drinking was driven by positive reinforcement (ie, reward drinkers) would have a better treatment response to naltrexone, whereas individuals whose drinking was driven by negative reinforcement (ie, relief drinkers) would have a better treatment response to acamprosate. The goal of the current analysis was to test this precision medicine hypothesis of the PREDICT study via analyses of subgroups. Results indicated that four phenotypes could be derived using the Inventory of Drinking Situations, a 30-item self-report questionnaire. These were high reward/high relief, high reward/low relief, low reward/high relief, and low reward/low relief phenotypes. Construct validation analyses provided strong support for the validity of these phenotypes. The subgroup of individuals who were predominantly reward drinkers and received naltrexone vs placebo had an 83% reduction in the likelihood of any heavy drinking (large effect size). Cutoff analyses were done for clinical applicability: individuals are reward drinkers and respond to naltrexone if their reward score was higher than their relief score AND their reward score was between 12 and 31. Using naltrexone with individuals who are predominantly reward drinkers produces significantly higher effect sizes than prescribing the medication to a more heterogeneous sample.

Dynamical state transitions into addictive behaviour and their early-warning signals

The theory of critical transitions in complex systems (ecosystems, climate, etc.), and especially its ability to predict abrupt changes by early-warning signals based on analysis of fluctuations close to tipping points, is seen as a promising avenue to study disease dynamics. However, the biomedical field still lacks a clear demonstration of this concept. Here, we used a well-established animal model in which initial alcohol exposure followed by deprivation and subsequent reintroduction of alcohol induces excessive alcohol drinking as an example of disease onset. Intensive longitudinal data (ILD) of rat drinking behaviour and locomotor activity were acquired by a fully automated drinkometer device over 14 weeks. Dynamical characteristics of ILD were extracted using a multi-scale computational approach. Our analysis shows a transition into addictive behaviour preceded by early-warning signals such as instability of drinking patterns and locomotor circadian rhythms, and a resultant increase in low frequency, ultradian rhythms during the first week of deprivation. We find evidence that during prolonged deprivation, a critical transition takes place pushing the system to excessive alcohol consumption. This study provides an adaptable framework for processing ILD from clinical studies and for examining disease dynamics and early-warning signals in the biomedical field.

Dynorphin and κ-Opioid Receptor Dysregulation in the Dopaminergic Reward System of Human Alcoholics

Molecular changes induced by excessive alcohol consumption may underlie formation of dysphoric state during acute and protracted alcohol withdrawal which leads to craving and relapse. A main molecular addiction hypothesis is that the upregulation of the dynorphin (DYN)/κ-opioid receptor (KOR) system in the nucleus accumbens (NAc) of alcohol-dependent individuals causes the imbalance in activity of D1- and D2 dopamine receptor (DR) expressing neural circuits that results in dysphoria. We here analyzed post-mortem NAc samples of human alcoholics to assess changes in prodynorphin (PDYN) and KOR (OPRK1) gene expression and co-expression (transcriptionally coordinated) patterns. To address alterations in D1- and D2-receptor circuits, we studied the regulatory interactions between these pathways and the DYN/KOR system. No significant differences in PDYN and OPRK1 gene expression levels between alcoholics and controls were evident. However, PDYN and OPRK1 showed transcriptionally coordinated pattern that was significantly different between alcoholics and controls. A downregulation of DRD1 but not DRD2 expression was seen in alcoholics. Expression of DRD1 and DRD2 strongly correlated with that of PDYN and OPRK1 suggesting high levels of transcriptional coordination between these gene clusters. The differences in expression and co-expression patterns were not due to the decline in neuronal proportion in alcoholic brain and thereby represent transcriptional phenomena. Dysregulation of DYN/KOR system and dopamine signaling through both alterations in co-expression patterns of opioid genes and decreased DRD1 gene expression may contribute to imbalance in the activity of D1- and D2-containing pathways which may lead to the negative affective state in human alcoholics.

ANCO-GeneDB: annotations and comprehensive analysis of candidate genes for alcohol, nicotine, cocaine and opioid dependence

Studies have shown that genetic factors play an important role in the risk to substance addiction and abuse. So far, various genetic and genomic studies have reported the related evidence. These rich, but highly heterogeneous, data provide us an unprecedented opportunity to systematically collect, curate and assess the genetic and genomic signals from published studies and to perform a comprehensive analysis of their features, functional roles and druggability. Such genetic data resources have been made available for other disease or phenotypes but not for major substance dependence yet. Here, we report comprehensive data collection and secondary analyses of four phenotypes of dependence: alcohol dependence, nicotine dependence, cocaine dependence and opioid dependence, collectively named as Alcohol, Nicotine, Cocaine and Opioid (ANCO) dependence. We built the ANCO-GeneDB, an ANCO-dependence-associated gene resource database. ANCO-GeneDB includes resources from genome-wide association studies and candidate gene-based studies, transcriptomic studies, methylation studies, literature mining and drug-target data, as well as the derived data such as spatial-temporal gene expression, promoters, enhancers and expression quantitative trait loci. All associated genes and genetic variants are well annotated by using the collected evidence. Based on the collected data, we performed integrative, secondary analyses to prioritize genes, pathways, eQTLs and tissues that are significantly enriched in ANCO-related phenotypes.

Reversing the Atypical Valuation of Drug and Nondrug Rewards in Smokers Using Multimodal Neuroimaging

BACKGROUND

Chronic substance use can disrupt the reward function of the anterior cingulate cortex (ACC), biasing the ACC to favor goal-directed behaviors that converge on drug use. Here we used multimodal neuroimaging methods to ask whether modulating reward-related signaling in the ACC can reverse the atypical valuation of nondrug and drug rewards in abstinent smokers.

METHODS

We first recorded functional magnetic resonance imaging data from 20 moderately dependent cigarette smokers (mean age = 25 years; no history of neuropsychiatric disorders), following an overnight period of abstinence, to identify regions of the left dorsal lateral prefrontal cortex associated with the anticipation of drug-related rewards (cigarette puff). Next, we recorded the reward positivity-an electrophysiological signal believed to index sensitivity of the ACC to rewards-while participants engaged in two feedback tasks to gain either monetary or cigarette rewards. Lastly, guided by functional magnetic resonance imaging data, a robotic arm positioned a repetitive transcranial magnetic stimulation coil over a subject-specific dorsal lateral prefrontal cortex target, and 50 repetitive transcranial magnetic stimulation pulses were delivered at 10 Hz (excitatory stimulation) immediately before each block of 10 trials of the money condition and at 1 Hz (inhibitory stimulation) before each block of 10 trials of the cigarette condition.

RESULTS

Our findings show that abstained smokers exhibited a heightened reward positivity to cigarette rewards relative to monetary rewards, and by applying excitatory or inhibitory repetitive transcranial magnetic stimulation to a subject-specific frontal-cingulate reward pathway, this pattern of results was reversed.

CONCLUSIONS

By modulating how the brain links value to drug and nondrug rewards, novel brain-based treatments may finally be on the horizon.

Dissociable Role of Corticotropin Releasing Hormone Receptor Subtype 1 on Dopaminergic and D1 Dopaminoceptive Neurons in Cocaine Seeking Behavior

The ability of many drugs of abuse, including cocaine, to mediate reinforcement and drug-seeking behaviors is in part mediated by the corticotropin-releasing hormone (CRH) system, in which CRH exerts its effects partly via the CRH receptor subtype 1 (CRHR1) in extra-hypothalamic areas. In fact, CRHR1 expressed in regions of the mesolimbic dopamine (DA) system have been demonstrated to modify cocaine-induced DA release and alter cocaine-mediated behaviors. Here we examined the role of neuronal selectivity of CRHR1 within the mesolimbic system on cocaine-induced behaviors. First we used a transgenic mouse line expressing GFP under the control of the Crhr1 promoter for double fluorescence immunohistochemistry to demonstrate the cellular location of CRHR1 in both dopaminergic and D1 dopaminoceptive neurons. We then studied cocaine sensitization, self-administration, and reinstatement in inducible CRHR1 knockouts using the CreERT2/loxP in either dopamine transporter (DAT)-containing neurons (DAT-Crhr1) or dopamine receptor 1 (D1)-containing neurons (D1-Crhr1). For sensitization testing, mice received five daily injections of cocaine (15 mg/kg IP). For self-administration, mice received eight daily 2 h cocaine (0.5 mg/kg per infusion) self-administration sessions followed by extinction and reinstatement testing. There were no differences in the acute or sensitized locomotor response to cocaine in DAT-Crhr1 or D1-Crhr1 mice and their respective controls. Furthermore, both DAT-Crhr1 and D1-Crhr1 mice reliably self-administered cocaine at the level of controls. However, DAT-Crhr1 mice demonstrated a significant increase in cue-induced reinstatement relative to controls, whereas D1-Crhr1 mice demonstrated a significant decrease in cue-induced reinstatement relative to controls. These data demonstrate the involvement of CRHR1 in cue-induced reinstatement following cocaine self-administration, and implicate a bi-directional role of CRHR1 for cocaine craving.

Harm reduction-a systematic review on effects of alcohol reduction on physical and mental symptoms

Based on the knowledge that alcohol misuse causes a multitude of diseases and increased mortality, this systematic review examines whether a reduction of the individual alcohol consumption can contribute to a minimization of health risks within a harm reduction approach. In fact, the reviewed 63 studies indicate that interventions aiming at alcohol reduction (including total abstinence as one possible therapeutic aim) indeed resulted in or were associated with positive effects in harmful, hazardous or alcohol-dependent drinkers. Major benefits were observed for reducing alcohol-associated injuries, recovery of ventricular heart function in alcoholic cardiomyopathy, blood pressure lowering, normalization of biochemical parameter, body weight reduction, histological improvement in pre-cirrhotic alcohol-related liver disease and slowed progression of an already existing alcohol-attributable liver fibrosis. Furthermore, reduced withdrawal symptoms, prevalence of psychiatric episodes and duration of in-patient hospital days, improvement of anxiety and depression symptoms, self-confidence, physical and mental quality of life, fewer alcohol-related adverse consequences as well as lower psychosocial stress levels and better social functioning can result from reduced alcohol intake. The reviewed literature demonstrated remarkable socioeconomic cost benefits in areas such as the medical health-care system or workforce productivity. Individuals with heightened vulnerability further benefit significantly from alcohol reduction (e.g. hypertension, hepatitis C, psychiatric co-morbidities, pregnancy, but also among adolescents and young adults). Concluding, the reviewed studies strongly support and emphasize the importance and benefits of early initial screening for problematic alcohol use followed by brief and other interventions in first contact medical health-care facilities to reduce alcohol intake.

Orbitofrontal structural markers of negative affect in alcohol dependence and their associations with heavy relapse-risk at 6 months post-treatment

BACKGROUND

Alcohol relapse is often occurring to regulate negative affect during withdrawal. On the neurobiological level, alcoholism is associated with gray matter (GM) abnormalities in regions that regulate emotional experience such as the orbitofrontal cortex (OFC). However, no study to our knowledge has investigated the neurobiological unpinning of affect in alcoholism at early withdrawal and the associations of OFC volume with long-term relapse risk.

METHODS

One hundred and eighty-two participants were included, 95 recently detoxified alcohol dependent patients (ADP) and 87 healthy controls (HC). We measured affective states using the positive and negative affect schedule (PANAS). We collected T1-weighted brain structural images and performed Voxel-based morphometry (VBM).

RESULTS

Findings revealed GM volume decrease in alcoholics in the prefrontal cortex (including medial OFC), anterior cingulate gyrus, and insula. GM volume in the medial OFC was positively associated with NA in the ADP group. Cox regression analysis predicted that risk to heavy relapse at 6 months increases with decreased GM volume in the medial OFC.

CONCLUSIONS

Negative affect during alcohol withdrawal was positively associated with OFC volume. What is more, increased GM volume in the OFC also moderated risk to heavy relapse at 6 months. Reduced GM in the OFC poses as risk to recovery from alcohol dependence and provides valuable insights into transient negative affect states during withdrawal that can trigger relapse. Implications exist for therapeutic interventions signifying the OFC as a neurobiological marker to relapse and could explain the inability of ADP to regulate internal negative affective states.

Adaptive dynamics of the 5-HT systems following chronic administration of selective serotonin reuptake inhibitors: a meta-analysis

Selective serotonin reuptake inhibitors (SSRIs) are the most frequently prescribed antidepressants. However, a major concern is their delayed onset of action, which is hypothesized to be associated with the time required for serotonin (5-HT) autoreceptors to desensitize, which should be reflected by actual neurochemical changes. Numerous in vivo microdialysis studies have been published that report on 5-HT levels in different brain sites following SSRI administration. Here, we performed a meta-analysis on dynamic changes of 5-HT neurotransmission during the course of chronic SSRI treatment. We conducted a meta-analysis on research articles of 5-HT neurotransmission measured by in vivo microdialysis in rat brain after subchronic and chronic SSRI administrations. In total, data from 42 microdialysis studies (798 rats) were analyzed. Within the first week of SSRI treatment, extracellular 5-HT concentrations drop in frontal cortex. Over the next 2 weeks of treatment, a linear increase in extracellular 5-HT levels up to 350% of prior treatment baseline is evident (n = 269). However, in hippocampus, prefrontal cortex, nucleus accumbens, and ventral tegmental area we found increased 5-HT levels within the first 3 days of SSRI administration. The time course of 5-HT dynamics in frontal cortex is in line with the hypothesis that 5-HT autoreceptors desensitize over 2-3 weeks of SSRI treatment and thereby enhanced extracellular 5-HT levels ensue. Yet, in other regions we did not find evidence supporting the traditional autoreceptor-mediated feedback loops hypothesis and thus other neurobiological adaptation mechanisms may also play a role in the delayed onset of SSRI action.

Changes in cerebral [18F]-FDG uptake induced by acute alcohol administration in a rat model of alcoholism

Several [¹⁸F]-FDG positron emission tomography (PET) studies in alcoholics have consistently reported decreases in overall brain glucose metabolism at rest and following acute alcohol administration. However, changes in cerebral glucose utilization associated with the transition to addiction are not well understood and require longitudinal translational imaging studies in animal models of alcoholism. Here, we studied brain glucose uptake in alcohol drinking rats in order to provide convergent evidence to what has previously been reported in human studies. Brain glucose metabolism was measured by [¹⁸F]-FDG microPET imaging in different male Wistar rat groups: short-term drinking (three months), long-term drinking (twelve months) and alcohol-naïve. Global and regional cerebral glucose uptake was measured at rest and following acute alcohol administration. We showed that alcohol significantly reduced the whole-brain glucose metabolism. This effect was most pronounced in the parietal cortex and cerebellum. Alcohol-induced decreases in brain [¹⁸F]-FDG uptake was most apparent in alcohol-naïve rats, less intense in short-term drinkers and absent in long-term drinkers. The latter finding indicates the occurrence of tolerance to the intoxicating effects of alcohol in long-term drinking individuals. In contrast, some regions, like the ventral striatum and entorhinal cortex, showed enhanced metabolic activity, an effect that did not undergo tolerance during long-term alcohol consumption. Our findings are comparable to those described in human studies using the same methodology. We conclude that [¹⁸F]-FDG PET studies in rat models of alcoholism provide good translation and can be used for future longitudinal studies investigating alterations in brain function during different stages of the addiction cycle.

Dorsolateral prefrontal cortex contributes to the impaired behavioral adaptation in alcohol dependence

Substance-dependent individuals often lack the ability to adjust decisions flexibly in response to the changes in reward contingencies. Prediction errors (PEs) are thought to mediate flexible decision-making by updating the reward values associated with available actions. In this study, we explored whether the neurobiological correlates of PEs are altered in alcohol dependence. Behavioral, and functional magnetic resonance imaging (fMRI) data were simultaneously acquired from 34 abstinent alcohol-dependent patients (ADP) and 26 healthy controls (HC) during a probabilistic reward-guided decision-making task with dynamically changing reinforcement contingencies. A hierarchical Bayesian inference method was used to fit and compare learning models with different assumptions about the amount of task-related information subjects may have inferred during the experiment. Here, we observed that the best-fitting model was a modified Rescorla-Wagner type model, the “double-update” model, which assumes that subjects infer the knowledge that reward contingencies are anti-correlated, and integrate both actual and hypothetical outcomes into their decisions. Moreover, comparison of the best-fitting model's parameters showed that ADP were less sensitive to punishments compared to HC. Hence, decisions of ADP after punishments were loosely coupled with the expected reward values assigned to them. A correlation analysis between the model-generated PEs and the fMRI data revealed a reduced association between these PEs and the BOLD activity in the dorsolateral prefrontal cortex (DLPFC) of ADP. A hemispheric asymmetry was observed in the DLPFC when positive and negative PE signals were analyzed separately. The right DLPFC activity in ADP showed a reduced correlation with positive PEs. On the other hand, ADP, particularly the patients with high dependence severity, recruited the left DLPFC to a lesser extent than HC for processing negative PE signals. These results suggest that the DLPFC, which has been linked to adaptive control of action selection, may play an important role in cognitive inflexibility observed in alcohol dependence when reinforcement contingencies change. Particularly, the left DLPFC may contribute to this impaired behavioral adaptation, possibly by impeding the extinction of the actions that no longer lead to a reward.

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Alcohol-dependent patients (ADP) had difficulty adapting to the reversals.

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The impaired adaptation was associated with a decrease in punishment sensitivity.

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The dorsolateral prefrontal cortex (DLPFC) of ADP failed to track prediction errors.

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A reduced tracking of the negative prediction error was present in the left DLPFC.

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The clinical severity of dependence was correlated with abnormal DLPFC activity.

Differential Roles for L-Type Calcium Channel Subtypes in Alcohol Dependence

It has previously been shown that the inhibition of L-type calcium channels (LTCCs) decreases alcohol consumption, although the contribution of the central LTCC subtypes Cav1.2 and Cav1.3 remains unknown. Here, we determined changes in Cav1.2 (Cacna1c) and Cav1.3 (Cacna1d) mRNA and protein expression in alcohol-dependent rats during protracted abstinence and naive controls using in situ hybridization and western blot analysis. Functional validation was obtained by electrophysiological recordings of calcium currents in dissociated hippocampal pyramidal neurons. We then measured alcohol self-administration and cue-induced reinstatement of alcohol seeking in dependent and nondependent rats after intracerebroventricular (i.c.v.) injection of the LTCC antagonist verapamil, as well as in mice with an inducible knockout (KO) of Cav1.2 in Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα)-expressing neurons. Our results show that Cacna1c mRNA concentration was increased in the amygdala and hippocampus of alcohol-dependent rats after 21 days of abstinence, with no changes in Cacna1d mRNA. This was associated with increased Cav1.2 protein concentration and L-type calcium current amplitudes. Further analysis of Cacna1c mRNA in the CA1, basolateral amygdala (BLA), and central amygdala (CeA) revealed a dynamic regulation over time during the development of alcohol dependence. The inhibition of central LTCCs via i.c.v. administration of verapamil prevented cue-induced reinstatement of alcohol seeking in alcohol-dependent rats. Further studies in conditional Cav1.2-KO mice showed a lack of dependence-induced increase of alcohol-seeking behavior. Together, our data indicate that central Cav1.2 channels, rather than Cav1.3, mediate alcohol-seeking behavior. This finding may be of interest for the development of new antirelapse medications.

Towards trans-diagnostic mechanisms in psychiatry: neurobehavioral profile of rats with a loss-of-function point mutation in the dopamine transporter gene

The research domain criteria (RDoC) matrix has been developed to reorient psychiatric research towards measurable behavioral dimensions and underlying mechanisms. Here, we used a new genetic rat model with a loss-of-function point mutation in the dopamine transporter (DAT) gene (Slc6a3_N157K) to systematically study the RDoC matrix. First, we examined the impact of the Slc6a3_N157K mutation on monoaminergic signaling. We then performed behavioral tests representing each of the five RDoC domains: negative and positive valence systems, cognitive, social and arousal/regulatory systems. The use of RDoC may be particularly helpful for drug development. We studied the effects of a novel pharmacological approach metabotropic glutamate receptor mGluR2/3 antagonism, in DAT mutants in a comparative way with standard medications. Loss of DAT functionality in mutant rats not only elevated subcortical extracellular dopamine concentration but also altered the balance of monoaminergic transmission. DAT mutant rats showed deficits in all five RDoC domains. Thus, mutant rats failed to show conditioned fear responses, were anhedonic, were unable to learn stimulus-reward associations, showed impaired cognition and social behavior, and were hyperactive. Hyperactivity in mutant rats was reduced by amphetamine and atomoxetine, which are well-established medications to reduce hyperactivity in humans. The mGluR2/3 antagonist LY341495 also normalized hyperactivity in DAT mutant rats without affecting extracellular dopamine levels. We systematically characterized an altered dopamine system within the context of the RDoC matrix and studied mGluR2/3 antagonism as a new pharmacological strategy to treat mental disorders with underlying subcortical dopaminergic hyperactivity.

Summary: The first systematic RDoc study of a disease mechanism proposes dopamine transporter DAT mutant rats as a model for drug development, targeting a hyperdopaminergic state.

Low μ-Opioid Receptor Status in Alcohol Dependence Identified by Combined Positron Emission Tomography and Post-Mortem Brain Analysis

Blockade of the μ-opioid receptor (MOR) by naltrexone reduces relapse risk in a subpopulation of alcohol-dependent patients. Previous positron-emission-tomography (PET) studies using the MOR ligand [¹¹C]carfentanil have found increased MOR availability in abstinent alcoholics, which may reflect either increased MOR expression or lower endogenous ligand concentration. To differentiate between both effects, we investigated two cohorts of alcoholic subjects using either post-mortem or clinical PET analysis. Post-mortem brain tissue of alcohol-dependent subjects and controls (N=43/group) was quantitatively analyzed for MOR ([³H]DAMGO)-binding sites and OPRM1 mRNA in striatal regions. [¹¹C]carfentanil PET was performed in detoxified, medication free alcohol-dependent patients (N=38), followed by a randomized controlled study of naltrexone versus placebo and follow-up for 1 year (clinical trial number: NCT00317031). Because the functional OPRM1 variant rs1799971:A>G affects the ligand binding, allele carrier status was considered in the analyses. MOR-binding sites were reduced by 23-51% in post-mortem striatal tissue of alcoholics. In the PET study, a significant interaction of OPRM1 genotype, binding potential (BP_ND) for [¹¹C]carfentanil in the ventral striatum, and relapse risk was found. Particularly in G-allele carriers, lower striatal BP_ND was associated with a higher relapse risk. Interestingly, this effect was more pronounced in the naltrexone treatment group. Reduced MOR is interpreted as a neuroadaptation to an alcohol-induced release of endogenous ligands in patients with severe alcoholism. Low MOR availability may explain the ineffectiveness of naltrexone treatment in this subpopulation. Finally, low MOR-binding sites are proposed as a molecular marker for a negative disease course.

Genetic studies of alcohol dependence in the context of the addiction cycle

Family, twin and adoption studies demonstrate clearly that alcohol dependence and alcohol use disorders are phenotypically complex and heritable. The heritability of alcohol use disorders is estimated at approximately 50-60% of the total phenotypic variability. Vulnerability to alcohol use disorders can be due to multiple genetic or environmental factors or their interaction which gives rise to extensive and daunting heterogeneity. This heterogeneity makes it a significant challenge in mapping and identifying the specific genes that influence alcohol use disorders. Genetic linkage and (candidate gene) association studies have been used now for decades to map and characterize genomic loci and genes that underlie the genetic vulnerability to alcohol use disorders. These approaches have been moderately successful in identifying several genes that contribute to the complexity of alcohol use disorders. Recently, genome-wide association studies have become one of the major tools for identifying genes for alcohol use disorders by examining correlations between millions of common single-nucleotide polymorphisms with diagnosis status. Genome-wide association studies are just beginning to uncover novel biology; however, the functional significance of results remains a matter of extensive debate and uncertainty. In this review, we present a select group of genome-wide association studies of alcohol dependence, as one example of a way to generate functional hypotheses, within the addiction cycle framework. This analysis may provide novel directions for validating the functional significance of alcohol dependence candidate genes. This article is part of the Special Issue entitled "Alcoholism".

Genetic Deletion of Neuronal PPARγ Enhances the Emotional Response to Acute Stress and Exacerbates Anxiety: An Effect Reversed by Rescue of Amygdala PPARγ Function

PPARγ is one of the three isoforms of the Peroxisome Proliferator-Activated Receptors (PPARs). PPARγ is activated by thiazolidinediones such as pioglitazone and is targeted to treat insulin resistance. PPARγ is densely expressed in brain areas involved in regulation of motivational and emotional processes. Here, we investigated the role of PPARγ in the brain and explored its role in anxiety and stress responses in mice. The results show that stimulation of PPARγ by pioglitazone did not affect basal anxiety, but fully prevented the anxiogenic effect of acute stress. Using mice with genetic ablation of neuronal PPARγ (PPARγ^NestinCre), we demonstrated that a lack of receptors, specifically in neurons, exacerbated basal anxiety and enhanced stress sensitivity. The administration of GW9662, a selective PPARγ antagonist, elicited a marked anxiogenic response in PPARγ wild-type (WT), but not in PPARγ^NestinCre knock-out (KO) mice. Using c-Fos immunohistochemistry, we observed that acute stress exposure resulted in a different pattern of neuronal activation in the amygdala (AMY) and the hippocampus (HIPP) of PPARγ^NestinCre KO mice compared with WT mice. No differences were found between WT and KO mice in hypothalamic regions responsible for hormonal response to stress or in blood corticosterone levels. Microinjection of pioglitazone into the AMY, but not into the HIPP, abolished the anxiogenic response elicited by acute stress. Results also showed that, in both regions, PPARγ colocalizes with GABAergic cells. These findings demonstrate that neuronal PPARγ is involved the regulation of the stress response and that the AMY is a key substrate for the anxiolytic effect of PPARγ.

SIGNIFICANCE STATEMENT

Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) is a classical target for antidiabetic therapies with thiazolidinedione compounds. PPARγ agonists such as rosiglitazone and pioglitazone are in clinical use for the treatment of insulin resistance. PPARγ has recently attracted attention for its involvement in the regulation of CNS immune response and functions. Here, we demonstrate that neuronal PPARγ activation prevented the negative emotional effects of stress and exerted anxiolytic actions without influencing hypothalamic-pituitary-adrenal axis function. Conversely, pharmacological blockade or genetic deletion of PPARγ enhanced anxiogenic responses and increased vulnerability to stress. These effects appear to be controlled by PPARγ neuronal-mediated mechanisms in the amygdala.

Validating the construct of aberrant salience in schizophrenia - Behavioral evidence for an automatic process

Suspecting significance behind ordinary events is a common feature in psychosis and it is assumed to occur due to aberrant salience attribution. The Salience Attribution Test (SAT; Roiser et al., 2009) measures aberrant salience as a bias towards one out of two equally reinforced cue features as opposed to adaptive salience towards features indicating high reinforcement. This is the first study to validate the latent constructs involved in salience attribution in patients. Forty-nine schizophrenia patients and forty-four healthy individuals completed the SAT, a novel implicit salience paradigm (ISP), a reversal learning task and a neuropsychological test battery. First, groups were compared on raw measures. Second and within patients, these were correlated and then used for a principal component analysis (PCA). Third, sum scores matching the correlation and component pattern were correlated with psychopathology. Compared to healthy individuals, patients exhibited more implicit aberrant salience in the SAT and ISP and less implicit and explicit adaptive salience attribution in the SAT. Implicit aberrant salience from the SAT and ISP positively correlated with each other and negatively with reversal learning. Whereas explicit aberrant salience was associated with cognition, implicit and explicit adaptive salience were positively correlated. A similar pattern emerged in the PCA and implicit aberrant salience was associated with negative symptoms. Taken together, implicit aberrant salience from the SAT and ISP seems to reflect an automatic process that is independent from deficient salience ascription to relevant events. Its positive correlation with negative symptoms might reflect motivational deficits present in chronic schizophrenia patients.

Metabolic shift of the kynurenine pathway impairs alcohol and cocaine seeking and relapse

RATIONALE

The glutamatergic system plays a key role in the maintenance of drug use and development of drug-related conditioned behaviours. In particular, hyper-glutamatergic activity and N-methyl-D-aspartate receptor (NMDAR) activation may drive drug craving and relapse. Inhibition of kynurenine-3-monooxygenase (KMO) shifts the metabolic kynurenine pathway towards production of kynurenic acid, which leads to a reduction of glutamatergic/NMDAR activity via different mechanisms.

OBJECTIVES

In this study, we investigated whether drug-seeking and relapse behaviour could be modified by the metabolic shift of endogenous kynurenine pathway.

METHODS

An inhibitor of kynurenine-3-monooxygenase (KMO) Ro61-8048 (4 and 40 mg/kg) and its prodrug JM6 (100 and 200 mg/kg) were tested in two behavioural rat models for drug seeking and relapse-the alcohol deprivation effect (ADE) model in long-term alcohol-drinking rats and the model of cue-induced reinstatement of alcohol- and cocaine-seeking behaviour.

RESULTS

Our results show that relapse-like alcohol drinking during the ADE was abolished by repeated intraperitoneal administration of Ro61-8048 and significantly reduced by its oral prodrug JM6. Cue-induced reinstatement of both alcohol- and cocaine-seeking behaviour was also abolished by administration of Ro61-8048.

CONCLUSIONS

Pharmacological enhancement of endogenous kynurenic acid levels provides a novel treatment strategy to interfere with glutamatergic/NMDAR activity as well as with craving and relapse in alcohol-dependent patients and drug addicts.

Largely overlapping neuronal substrates of reactivity to drug, gambling, food and sexual cues: A comprehensive meta-analysis

Cue reactivity to natural and social rewards is essential for motivational behavior. However, cue reactivity to drug rewards can also elicit craving in addicted subjects. The degree to which drug and natural rewards share neural substrates is not known. The objective of this study is to conduct a comprehensive meta-analysis of neuroimaging studies on drug, gambling and natural stimuli (food and sex) to identify the common and distinct neural substrates of cue reactivity to drug and natural rewards. Neural cue reactivity studies were selected for the meta-analysis by means of activation likelihood estimations, followed by sensitivity and clustering analyses of averaged neuronal response patterns. Data from 176 studies (5573 individuals) suggests largely overlapping neural response patterns towards all tested reward modalities. Common cue reactivity to natural and drug rewards was expressed by bilateral neural responses within anterior cingulate gyrus, insula, caudate head, inferior frontal gyrus, middle frontal gyrus and cerebellum. However, drug cues also generated distinct activation patterns in medial frontal gyrus, middle temporal gyrus, posterior cingulate gyrus, caudate body and putamen. Natural (sexual) reward cues induced unique activation of the pulvinar in thalamus. Neural substrates of cue reactivity to alcohol, drugs of abuse, food, sex and gambling are largely overlapping and comprise a network that processes reward, emotional responses and habit formation. This suggests that cue-mediated craving involves mechanisms that are not exclusive for addictive disorders but rather resemble the intersection of information pathways for processing reward, emotional responses, non-declarative memory and obsessive-compulsive behavior.

A gene-by-sex interaction for nicotine reward: evidence from humanized mice and epidemiology

It has been proposed that vulnerability to nicotine addiction is moderated by variation at the μ-opioid receptor locus (OPRM1), but results from human studies vary and prospective studies based on genotype are lacking. We have developed a humanized mouse model of the most common functional OPRM1 polymorphism rs1799971_A>G (A118G). Here we use this model system together with a cohort of German youth to examine the role of the OPRM1 A118G variation on nicotine reward. Nicotine reinforcement was examined in the humanized mouse model using i.v. self-administration. Male (n=17) and female (n=26) mice homozygous either for the major human A allele (AA) or the minor G allele (GG) underwent eight daily 2 h sessions of nicotine self-administration. Furthermore, male (n=104) and female (n=118) subjects homozygous for the A allele or carrying the G allele from the Mannheim Study of Children at Risk were evaluated for pleasurable and unpleasant experiences during their initial smoking experience. A significant sex-by-genotype effect was observed for nicotine self-administration. Male 118GG mice demonstrated higher nicotine intake than male 118AA mice, suggesting increased nicotine reinforcement. In contrast, there was no genotype effect in female mice. Human male G allele carriers reported increased pleasurable effects from their first smoking experience, as compared to male homozygous A, female G and female homozygous A allele carriers. The 118G allele appears to confer greater sensitivity to nicotine reinforcement in males, but not females.

Alcohol preference and consumption are controlled by the caudal linear nucleus in alcohol-preferring rats

The neuroanatomical and neurochemical basis of alcohol drinking has been extensively studied, but the neural circuitry mediating alcohol reinforcement has not been fully delineated. In the present experiments, we used both neuroimaging and pharmacological tools to identify neural systems associated with alcohol preference and high voluntary alcohol drinking in alcohol-preferring AA (Alko Alcohol) rats. First, we compared the basal brain activity of AA rats with that of heterogeneous Wistar rats with manganese-enhanced magnetic resonance imaging (MEMRI). Briefly, alcohol-naïve rats were implanted with subcutaneous osmotic minipumps delivering 120 mg/kg MnCl2 over a 7-day period, and were then imaged using a three-dimensional rapid acquisition-relaxation enhanced pulse sequence. MEMRI analysis revealed that the most conspicuous subcortical activation difference was located in the caudal linear nucleus of raphe (CLi), with AA rats displaying significantly lower T1 signal in this region compared to Wistar rats. However, following long-term alcohol drinking, CLi activity was increased in AA rats. In the second experiment, the CLi was targeted with pharmacological tools. AA rats trained to drink 10% alcohol during 2-h sessions were implanted with guide cannulas aimed at the CLi and were given injections of the GABAA receptor agonist muscimol into the CLi before drinking sessions. Muscimol dose-dependently increased alcohol drinking, and co-administration of the gamma aminobutyric acid (GABA)A antagonist bicuculline blocked muscimol's effect. These findings suggest that the mediocaudal region of the ventral tegmental area, particularly the CLi, is important for the propensity for high alcohol drinking and controls alcohol reward via GABAergic transmission.

Context- and time-dependent neurobiological and behavioral sensitization induced by a single morphine exposure in mice

RATIONALE

Drug-induced sensitization in the mesocorticolimbic systems is thought to play an important role in certain aspects of drug addiction, including the involvement of drug-associated cues and environments in mediating drug-seeking behaviors. Our previous studies have identified the significance of heat shock protein 70 (Hsp70) in the development of a single morphine exposure-induced behavioral sensitization.

OBJECTIVES

The present study expands upon these findings by investigating the effect of environment on the expression of behavioral sensitization induced by a single morphine exposure, and the potential involvement of Hsp70 protein levels in these effects.

METHODS

Mice were pretreated with a single morphine injection in test chambers (morphine-paired) or home cages (morphine-unpaired) on day 1 and challenged on day 2 or 8, in test chambers. Hsp70 expression in the nucleus accumbens (NAc) was analyzed after the challenge.

RESULTS

The expression of single morphine exposure-induced behavioral sensitization was accompanied by a significant increase in Hsp70 expression in NAc. In contrast, the unpaired morphine-treated group failed to exhibit behavioral sensitization or higher Hsp70 expression. Additionally, by adding a habituation process prior to the challenge, we demonstrated that conditioned hyperactivity, which was not accompanied by an increased expression of Hsp70, is not essential for behavioral sensitization.

CONCLUSIONS

Behavioral sensitization induced by a single morphine exposure in mice exhibits context and time dependency, with environmental context likely functioning via an inhibitory conditioning mechanism. Furthermore, alterations in Hsp70 expression in the NAc may represent a neurobiological sensitization mechanism mediating context- and time-dependent behavioral sensitization.

A Genetic Animal Model of Alcoholism for Screening Medications to Treat Addiction

The purpose of this review is to present up-to-date pharmacological, genetic, and behavioral findings from the alcohol-preferring P rat and summarize similar past work. Behaviorally, the focus will be on how the P rat meets criteria put forth for a valid animal model of alcoholism with a highlight on its use as an animal model of polysubstance abuse, including alcohol, nicotine, and psychostimulants. Pharmacologically and genetically, the focus will be on the neurotransmitter and neuropeptide systems that have received the most attention: cholinergic, dopaminergic, GABAergic, glutamatergic, serotonergic, noradrenergic, corticotrophin releasing hormone, opioid, and neuropeptide Y. Herein, we sought to place the P rat's behavioral and neurochemical phenotypes, and to some extent its genotype, in the context of the clinical literature. After reviewing the findings thus far, this chapter discusses future directions for expanding the use of this genetic animal model of alcoholism to identify molecular targets for treating drug addiction in general.

Chronic intermittent ethanol exposure in mice leads to an up-regulation of CRH/CRHR1 signaling

BACKGROUND

One of the most commonly used approaches to induce ethanol (EtOH) dependence in rodents is EtOH vapor inhalation. This procedure requires the co-administration of pyrazole-an inhibitor of the alcohol dehydrogenase-to obtain stable blood EtOH concentrations (BECs) during the entire induction course. However, pyrazole can produce unwanted side effects. Our goal was to obtain EtOH-dependent mice without pyrazole and to study their behavioral and molecular postdependent phenotype. In particular, we were interested in alterations in the corticotrophin-releasing hormone (CRH) and receptor (CRHR1 and CRHR2) system as a prominent role of CRH in driving the postdependent state via actions in the central extended amygdala (CeA) has been demonstrated in rats but not in postdependent mice.

METHODS

We established an alternative model of chronic intermittent EtOH (CIE) inhalation without the use of pyrazole in C57BL/6N mice. Our CIE exposure protocol involved 8 cycles. One cycle consisted of 8 hours with EtOH inhalation and 8 hours without EtOH. We then examined withdrawal symptoms. After 2 weeks of abstinence, we studied relapse, reinstatement of EtOH-seeking, and stress-induced EtOH self-administration. We also did transcriptional analysis of components of the CRH system during CIE, protracted abstinence, and after stress-induced EtOH self-administration.

RESULTS

CIE exposure without pyrazole resulted in reproducible BECs during the induction procedure. Mice showed strong withdrawal scores during 4 to 12 hours after the last CIE cycle and enhanced stress-induced EtOH self-administration. This postdependent phenotype during abstinence was accompanied by enhanced Crh and Crhr1 transcripts but no change in Crhr2 transcripts in the CeA. Cue-induced EtOH-seeking behavior and relapse (alcohol deprivation effect) were not affected by the inhalation procedure.

CONCLUSIONS

We have established a CIE inhalation protocol without pyrazole in mice and showed excessive EtOH self-administration under mild stress and enhanced CRH/CRHR1 signaling in the CeA.

Glutamate Receptors within the Mesolimbic Dopamine System Mediate Alcohol Relapse Behavior

Glutamatergic input within the mesolimbic dopamine (DA) pathway plays a critical role in the development of addictive behavior. Although this is well established for some drugs of abuse, it is not known whether glutamate receptors within the mesolimbic system are involved in mediating the addictive properties of chronic alcohol use. Here we evaluated the contribution of mesolimbic NMDARs and AMPARs in mediating alcohol-seeking responses induced by environmental stimuli and relapse behavior using four inducible mutant mouse lines lacking the glutamate receptor genes Grin1 or Gria1 in either DA transporter (DAT) or D1R-expressing neurons. We first demonstrate the lack of GluN1 or GluA1 in either DAT- or D1R-expressing neurons in our mutant mouse lines by colocalization studies. We then show that GluN1 and GluA1 receptor subunits within these neuronal subpopulations mediate the alcohol deprivation effect, while having no impact on context- plus cue-induced reinstatement of alcohol-seeking behavior. We further validated these results pharmacologically by demonstrating similar reductions in the alcohol deprivation effect after infusion of the NMDAR antagonist memantine into the nucleus accumbens and ventral tegmental area of control mice, and a rescue of the mutant phenotype via pharmacological potentiation of AMPAR activity using aniracetam. In conclusion, dopamine neurons as well as D1R-expressing medium spiny neurons and their glutamatergic inputs via NMDARs and AMPARs act in concert to influence relapse responses. These results provide a neuroanatomical and molecular substrate for relapse behavior and emphasize the importance of glutamatergic drugs in modulating relapse behavior.

SIGNIFICANCE STATEMENT

Here we provide genetic and pharmacological evidence that glutamate receptors within the mesolimbic dopamine system play an essential role in alcohol relapse. Using various inducible and site-specific transgenic mouse models and pharmacological validation experiments, we show that critical subunits of NMDARs and AMPARs expressed either in dopamine neurons or in dopamine receptor D1-containing neurons play an important role in the alcohol deprivation effect (the increase in alcohol intake after a period of abstinence) while having no impact on context- plus cue-induced reinstatement of alcohol-seeking responses. Medications targeting glutamatergic neurotransmission by selective inactivation of these glutamate receptors might have therapeutic efficacy.

The Calpain Inhibitor A-705253 Attenuates Alcohol-Seeking and Relapse with Low Side-Effect Profile

Preclinical studies revealed contribution of N-methyl-D-aspartate receptors (NMDARs) to a variety of neuropsychiatric diseases including alcoholism, but development of NMDAR antagonists for therapeutic use has been a challenge, in part due to severe side effects. One of the key intracellular events resulting from stimulation of NMDAR is activation of calpains-calcium-dependent cysteine proteases. Here we studied whether inhibition of calpains would produce therapeutic-like effects of NMDAR antagonists but without their NMDAR-mediated side-effect profile. The calpain inhibitor A-705253 (3-10 mg/kg) was tested in a model of cue-induced reinstatement of alcohol-seeking behavior in post-dependent Wistar rats and in an alcohol deprivation effect (ADE) model in long-term alcohol drinking Wistar rats, two behavioral models for alcohol-seeking and relapse, respectively. We also tested the effect of A-705253 on the saccharine deprivation effect (SDE) as a selectivity measure. Acute treatment with A-705253 dose-dependently reduced cue-induced reinstatement of alcohol-seeking behavior. Repeated administration of A-705253 caused significant reductions of relapse-like excessive alcohol intake during the post-abstinence drinking days, an effect that persisted during two more successive drug-free drinking weeks, which was selective for the ADE as the SDE was unaffected. However, A-705253 did not produce psychostimulant, cognition impairing (delayed-matching-to-position), or psychotomimetic effects (specifically, phencyclidine discriminative stimulus effects). Taken together, these results demonstrate the involvement of calpains in alcohol-seeking and relapse and present a rationale for a novel pharmacological intervention that may reduce craving and relapse with minimal side effects in alcohol-dependent patients.