Nicotinic Mechanisms Modulate Ethanol Withdrawal and Modify Time Course and Symptoms Severity of Simultaneous Withdrawal from Alcohol and Nicotine

Mutation of the α5 nicotinic acetylcholine receptor subunit increases ethanol and nicotine consumption in adolescence and impacts adult drug consumption

Alcohol and nicotine are commonly used during adolescence, establishing long-lasting neuroplastic alterations that influence subsequent drug use and abuse. Drinking- and smoking-related traits have been extensively associated with variation in CHRNA5 - the gene that encodes the α5 subunit of neuronal nicotinic acetylcholine receptors (nAChRs). The single nucleotide polymorphism (SNP) rs16969968 in CHRNA5 encodes an amino acid substitution (D398N) that alters the function and pharmacokinetics of α5-containing nAChR. When expressed in rodents, this variant results in increased ethanol and nicotine operant self-administration. How disruption of α5-containing nAChRs influences adolescent ethanol and nicotine intake, and how it modulates interactions between these drugs has not been previously explored. In the present study, we examined volitional ethanol and nicotine consumption in adolescent mice (post-natal day 30-43) of both sexes with mutated (SNP) or lacking (KO) the α5 nAChR subunit. The effect of adolescent alcohol or nicotine exposure on home cage consumption of the opposite drug in adulthood and its modulation by Chrna5 mutation and sex were examined. During adolescence, we found that α5 nAChR disruption increases nicotine intake in mice of both sexes, but the effect on alcohol intake was only observed in females. The sex-specific increase in alcohol consumption in α5 SNP and KO was replicated in adulthood. The effect of adolescent alcohol or nicotine exposure on subsequent intake of the opposite drug in adulthood is modulated by sex and Chrna5 mutation. These observations suggest sex differences in the genetic architecture of alcohol dependence, and modulators of alcohol and nicotine interactions.

Behavioral characterization of withdrawal following chronic voluntary ethanol consumption via intermittent two-bottle choice points to different susceptibility categories

BACKGROUND

Alcohol is among the most commonly abused drugs worldwide. Cessation of chronic alcohol consumption can result in the appearance of withdrawal symptoms that commonly promote relapse in individuals with alcohol use disorder (AUD). Thus, preclinical models of voluntary alcohol consumption, in which animals manifest spontaneous signs of withdrawal after alcohol cessation, can be useful for studying AUD and its treatment. The intermittent two-bottle choice paradigm (I2BC) has been used extensively to examine alcohol intake in rodents. However, previous studies have reported conflicting observations regarding its potential to result in the spontaneous manifestation of withdrawal upon alcohol cessation.

METHODS

We employed a battery of behavioral tests to examine the emergence of affective and physical signs of withdrawal in female and male mice exposed to alcohol in the I2BC for 10 weeks. Specifically, mice of both sexes undergoing 24-h withdrawal from the I2BC were tested for physical signs of withdrawal, anxiety-like behavior in the open field arena (OFA) and elevated plus maze (EPM), and anxiety/compulsive-like behavior in the marble burying test (MBT). The main outcomes from these tests were combined into a behavioral severity score to describe the overall behavioral phenotype.

RESULTS

Both female and male mice undergoing withdrawal from the I2BC displayed elevated physical signs of withdrawal and anxiety-associated behavior in the EPM and MBT. Analysis of the overall behavioral severity score revealed more severe phenotypes in female and male mice undergoing withdrawal from the I2BC than controls. Additionally, stratification of the mice based on severity scores demonstrated a differential distribution of severities between the exposure groups.

CONCLUSIONS

We confirmed that a significant fraction of mice chronically exposed to alcohol in the I2BC display spontaneous withdrawal. In addition, we showed that computing a severity score from a combination of behavioral metrics can be useful in preclinical research to model evaluation tools used in patients with AUD.

Effect of Combination Treatment With Varenicline and Nicotine Patch on Smoking Cessation Among Smokers Who Drink Heavily: A Randomized Clinical Trial

IMPORTANCE

The concurrent use of both tobacco and alcohol causes substantial disease and early mortality, and smokers who drink heavily tend to be less successful in smoking cessation than smokers who do not. Although varenicline combined with nicotine replacement therapy for smoking cessation has been examined among smokers who do not drink heavily, this combination treatment has not yet been examined among smokers who drink heavily.

OBJECTIVE

To determine whether combined treatment with varenicline tartrate and nicotine patch improves continuous abstinence from cigarette smoking among smokers who drink heavily.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled, superiority randomized clinical trial evaluated combined treatment with varenicline and nicotine patch compared with placebo and nicotine patch for smoking cessation (primary outcome) and drinking behavior (secondary outcome) among smokers who drink heavily. The clinical trial was conducted at 2 outpatient sites in Chicago, Illinois, with enrollment from March 26, 2018, to February 14, 2020. The 122 participants were recruited from the community via social media and public transit advertisements and equally randomized to the 2 treatment groups, which were stratified by sex and smoking behavior. Eligible participants smoked between 5 and 30 cigarettes per day and drank heavily (>14 drinks per week for men or >7 drinks per week for women and ≥1 heavy drinking day [defined as >5 drinks per occasion for men or >4 drinks per occasion for women] per month for the past year) and had a desire to quit smoking.

INTERVENTIONS

Varenicline tartrate, 1.0 mg, twice daily or matching placebo pills twice daily for 12 weeks. Nicotine patch at manufacturer-recommended doses for 10 weeks and brief individual smoking cessation counseling the week before the quit date and on the quit date.

MAIN OUTCOMES AND MEASURES

The primary outcome was self-reported continuous cigarette abstinence through weeks 9 to 12; abstinence was biochemically confirmed at the week 12 study visit. Secondary outcomes were the frequency of weekly drinking and weekly heavy drinking during the study period.

RESULTS

Among 122 participants (mean [SD] age, 44.0 [12.4] years; 67 men [54.9%]), 61 were randomly assigned to receive combined treatment with varenicline and nicotine patch (varenicline group), and 61 were randomly assigned to receive placebo and nicotine patch (placebo group). A total of 54 participants (44.3%) self-identified as Black, 56 (45.9%) as White, and 12 (9.8%) as other races (including American Indian or Alaska Native, Asian, >1 race, and unspecified race). A total of 8 participants (6.6%) self-identified as Hispanic and 114 (93.4%) as non-Hispanic ethnicity. Study retention to 12 weeks was 89%. The intention-to-treat analyses showed higher smoking cessation rates during weeks 9 to 12 in the varenicline group vs the placebo group (27 participants [44.3%] vs 17 participants [27.9%]; odds ratio, 2.20; 95% CI, 1.01-4.80; P = .047) and lower likelihood of relapse throughout treatment in the varenicline group relative to the placebo group (hazard ratio, 0.62; 95% CI, 0.40-0.96; P = .03). Both treatments were well tolerated; however, compared with participants in the placebo group, those in the varenicline group experienced more adverse effects, with 5 participants in the varenicline group discontinuing medication due to adverse effects.

CONCLUSIONS AND RELEVANCE

In this study, combined treatment with varenicline and nicotine patch was more effective than placebo and nicotine patch for smoking cessation among smokers who drink heavily. The combination treatment had no effect on alcohol consumption, with both groups showing significant reductions. Combination treatment with varenicline and nicotine patch may be a viable option for smokers who drink heavily.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02859142.

α-Conotoxin TxIB Improved Behavioral Abnormality and Changed Gene Expression in Zebrafish (Danio rerio) Induced by Alcohol Withdrawal

Background and Purpose: Alcohol use disorder (AUD) is a serious public health issue and affects the lives of numerous people. Previous studies have shown a link between nicotinic acetylcholine receptors (nAChR) and alcohol addiction. However, the role of α6β2* nAChR in alcohol addiction remains obscure, and whether α6β2* nAChR can be used as a potential drug target for alcohol withdrawal need to be studied.

Methods: Zebrafish (Danio rerio) were exposed to 0.2% alcohol for 14 days followed by 7 days of repeated withdrawal and then retro-orbitally injected with α-conotoxin TxIB (a selective α6β2* nAChR antagonist). Open Field Test was applied to characterize zebrafish behavior parameters. The monoamine neurotransmitter amounts and their mRNA expression in the zebrafish brain were identified using ELISA and quantitative real-time PCR (RT-PCR). RNA-sequencing (RNA-seq) and subsequent bioinformatics analysis were employed to explore the potential network regulation of TxIB after alcohol withdrawal.

Results: The max speed in the center area of the Open Field Test was significantly higher in the withdrawal group whereas TxIB injection corrected this abnormality. The amount and mRNA expression of monoamine neurotransmitters did not change significantly after alcohol withdrawal and TxIB administration. RNA sequencing of zebrafish brain indicated a total of 657 genes showed aberrant expression and among which 225 were reversed after TxIB injection. These reversed genes were significantly enriched in the calcium ion binding pathway and the gene expression profile was further validated by RT-PCR.

Conclusion: Our finding suggests α-conotoxin TxIB improved behavioral abnormality induced by alcohol-withdrawal, and changed gene expression mainly in the calcium signaling pathway. Therefore, α-conotoxin TxIB is expected to become a potential therapeutic agent for alcohol withdrawal.

Antagonism of GluK1-containing kainate receptors reduces ethanol consumption by modulating ethanol reward and withdrawal

Alcohol use disorder (AUD) is a neuropsychiatric condition affecting millions of people worldwide. Topiramate (TPM) is an antiepileptic drug that has been shown to reduce ethanol drinking in humans. However, TPM is associated with a variety of adverse effects due to its interaction with many receptor systems and intracellular pathways. GluK1-containing kainate receptors (GluK1*KARs) are non-selectively inhibited by TPM, and genetic association studies suggest that this receptor system could be targeted to reduce drinking in AUD patients. We examined the efficacy of LY466195, a selective inhibitor of GluK1*KAR, in reducing ethanol consumption in the intermittent two-bottle choice paradigm in mice. The effect of LY466195 on various ethanol-related phenotypes was investigated by quantification of alcohol intake, physical signs of withdrawal, conditioned place preference (CPP) and in vivo microdialysis in the nucleus accumbens. Selective GluK1*KAR inhibition reduced ethanol intake and preference in a dose-dependent manner. LY466195 treatment attenuated the physical manifestations of ethanol withdrawal and influenced the rewarding properties of ethanol. Interestingly, LY466195 injection also normalized changes in dopamine levels in response to acute ethanol in ethanol-dependent mice, but had no effect in ethanol-naïve mice, suggesting ethanol state-dependent effects. The data point to GluK1*KARs as an attractive pharmacological target for the treatment of AUD.

Research Needs for Inpatient Management of Severe Alcohol Withdrawal Syndrome: An Official American Thoracic Society Research Statement

Background: Severe alcohol withdrawal syndrome (SAWS) is highly morbid, costly, and common among hospitalized patients, yet minimal evidence exists to guide inpatient management. Research needs in this field are broad, spanning the translational science spectrum. Goals: This research statement aims to describe what is known about SAWS, identify knowledge gaps, and offer recommendations for research in each domain of the Institute of Medicine T0-T4 continuum to advance the care of hospitalized patients who experience SAWS. Methods: Clinicians and researchers with unique and complementary expertise in basic, clinical, and implementation research related to unhealthy alcohol consumption and alcohol withdrawal were invited to participate in a workshop at the American Thoracic Society 2019 International Conference. The committee was subdivided into four groups on the basis of interest and expertise: T0-T1 (basic science research with translation to humans), T2 (research translating to patients), T3 (research translating to clinical practice), and T4 (research translating to communities). A medical librarian conducted a pragmatic literature search to facilitate this work, and committee members reviewed and supplemented the resulting evidence, identifying key knowledge gaps. Results: The committee identified several investigative opportunities to advance the care of patients with SAWS in each domain of the translational science spectrum. Major themes included 1) the need to investigate non-γ-aminobutyric acid pathways for alcohol withdrawal syndrome treatment; 2) harnessing retrospective and electronic health record data to identify risk factors and create objective severity scoring systems, particularly for acutely ill patients with SAWS; 3) the need for more robust comparative-effectiveness data to identify optimal SAWS treatment strategies; and 4) recommendations to accelerate implementation of effective treatments into practice. Conclusions: The dearth of evidence supporting management decisions for hospitalized patients with SAWS, many of whom require critical care, represents both a call to action and an opportunity for the American Thoracic Society and larger scientific communities to improve care for a vulnerable patient population. This report highlights basic, clinical, and implementation research that diverse experts agree will have the greatest impact on improving care for hospitalized patients with SAWS.

Does nicotine exposure during adolescence modify the course of schizophrenia-like symptoms? Behavioral analysis in a phencyclidine-induced mice model

The first symptoms of schizophrenia (SCHZ) are usually observed during adolescence, a developmental period during which first exposure to psychoactive drugs also occurs. These epidemiological findings point to adolescence as critical for nicotine addiction and SCHZ comorbidity, however it is not clear whether exposure to nicotine during this period has a detrimental impact on the development of SCHZ symptoms since there is a lack of studies that investigate the interactions between these conditions during this period of development. To elucidate the impact of a short course of nicotine exposure across the spectrum of SCHZ-like symptoms, we used a phencyclidine-induced adolescent mice model of SCHZ (2.5mg/Kg, s.c., daily, postnatal day (PN) 38-PN52; 10mg/Kg on PN53), combined with an established model of nicotine minipump infusions (24mg/Kg/day, PN37-44). Behavioral assessment began 4 days after the end of nicotine exposure (PN48) using the following tests: open field to assess the hyperlocomotion phenotype; novel object recognition, a declarative memory task; three-chamber sociability, to verify social interaction and prepulse inhibition, a measure of sensorimotor gating. Phencyclidine exposure evoked deficits in all analyzed behaviors. Nicotine history reduced the magnitude of phencyclidine-evoked hyperlocomotion and impeded the development of locomotor sensitization. It also mitigated the deficient sociability elicited by phencyclidine. In contrast, memory and sensorimotor gating deficits evoked by phencyclidine were neither improved nor worsened by nicotine history. In conclusion, our results show for the first time that nicotine history, restricted to a short period during adolescence, does not worsen SCHZ-like symptoms evoked by a phencyclidine-induced mice model.

Exposure to fruit-flavoring during adolescence increases nicotine consumption and promotes dose escalation

The rise of e-cigarette popularity has sparked interest in the role of palatable flavors on nicotine use. Despite growing evidence that sweet flavorants enhance nicotine reward, their influence on nicotine consumption has not been studied extensively. In addition, the impact that flavored nicotine use in adolescence could have on nicotine reward and dependence in adulthood remains unclear. This study examined the role of flavored nicotine access on nicotine preference and consumption longitudinally, from adolescence to adulthood. Male and female adolescent mice preferred a fruit-flavored nicotine solution over an unflavored nicotine solution. However, only adolescent female mice with access to flavored nicotine consumed higher doses. Furthermore, while adolescent male mice escalated consumption of both flavored and unflavored nicotine, female mice only escalated nicotine consumption when given access to flavored nicotine. As mice matured into adulthood, there was no evidence that a history of flavored-nicotine access altered preference for unflavored nicotine compared to a nicotine-free control in a classic two-bottle choice design. However, when the nicotine concentration was progressively reduced, mice that had consumed strawberry-flavored nicotine in adolescence maintained baseline nicotine consumption levels longer than mice that initiated nicotine use without flavor in adolescence. Finally, addition of fruit-flavorants into the nicotine solution during adulthood led to nicotine preference and increased levels of nicotine consumption, regardless of previous flavored-nicotine access or of familiarity with the selected flavorant. These results indicate that flavorants increase nicotine consumption independent of life stage, possibly posing a disproportionate risk to adolescent females. Our results also point to an effect of adolescent flavored-nicotine use on nicotine dose maintenance in adulthood, which could have implications for the success of future quit attempts.

Tobacco dependence management in a smoke-free inpatient drug and alcohol unit

OBJECTIVE

Various smoke-free policies and practices (carbon monoxide monitoring, nicotine replacement therapy, pharmacotherapy, behavioural interventions) have been introduced to manage tobacco dependence in inpatient drug and alcohol facilities. Since the introduction of a smoke-free policy to our inpatient drug and alcohol facility, there has been no objective evaluation of its practices or patients' views.

METHODS

We administered a questionnaire to 42 inpatients identified as smokers. A retrospective record review was performed on those patients for demographic data, substance use, psychiatric conditions and tobacco dependence assessment and management. Descriptive analyses and tests of association were conducted. Open-ended questions were subjected to content analysis.

RESULTS

Tobacco dependence assessment was mostly completed with daily cigarette consumption documented for 41 (98%), time to first cigarette for 39 (93%) and CO monitoring performed for 42 (100%) patients. Patients' views of the various management strategies were positive, although many were underutilised. Those with high tobacco dependence were more likely to approve of nicotine replacement therapy patches than those with low tobacco dependence (p = 0.009).

CONCLUSION

The results demonstrate that while the various interventions provided were reported to be helpful, many were underutilised. Future research could consider why certain strategies were not utilised and help improve uptake.

Nicotinic acetylcholine receptors and nicotine addiction: A brief introduction

Nicotine is a highly addictive drug found in tobacco that drives its continued use despite the harmful consequences. The initiation of nicotine abuse involves the mesolimbic dopamine system, which contributes to the rewarding sensory stimuli and associative learning processes in the beginning stages of addiction. Nicotine binds to neuronal nicotinic acetylcholine receptors (nAChRs), which come in a diverse collection of subtypes. The nAChRs that contain the α4 and β2 subunits, often in combination with the α6 subunit, are particularly important for nicotine's ability to increase midbrain dopamine neuron firing rates and phasic burst firing. Chronic nicotine exposure results in numerous neuroadaptations, including the upregulation of particular nAChR subtypes associated with long-term desensitization of the receptors. When nicotine is no longer present, for example during attempts to quit smoking, a withdrawal syndrome develops. The expression of physical withdrawal symptoms depends mainly on the α2, α3, α5, and β4 nicotinic subunits in the epithalamic habenular complex and its target regions. Thus, nicotine affects diverse neural systems and an array of nAChR subtypes to mediate the overall addiction process. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

The role of nicotinic acetylcholine receptors in alcohol-related behaviors

Alcohol use disorder (AUD) causes an alarming economic and health burden in the United States. Unfortunately, this disease does not exist in isolation; AUD is highly comorbid with nicotine use. Results from both human and animal models demonstrate a genetic correlation between alcohol and nicotine behaviors. These data support the idea of shared genetic and neural mechanisms underlying these behaviors. Nicotine acts directly at nicotinic acetylcholine receptors (nAChR) to have its pharmacological effect. Interestingly, alcohol also acts both directly and indirectly at these receptors. Research utilizing genetically engineered rodents and pharmacological manipulations suggest a role for nAChR in several ethanol behaviors. The current manuscript collates this literature and discusses findings that implicate specific nAChR subunits in ethanol phenotypes. These data suggest future directions for targeting nAChR as novel therapeutics for AUD.

Interventions for pregnant women who use tobacco and other substances: a systematic review protocol

INTRODUCTION

The prevalence of tobacco smoking in pregnancy remains elevated in some disadvantaged populations of women. One group is those who use alcohol and/or other psychoactive substances during pregnancy, with tobacco use prevalence estimates ranging from 71% to 95%. Although effective evidence-based cessation treatments exist, few women with co-occurring substance use problems successfully stop smoking during pregnancy. There is limited information about treatments that specifically target this group and a summary of the available research is required to assist and enhance the development of innovative cessation interventions. This article describes a protocol for a comprehensive review of studies that have trialled behavioural and/or pharmacological tobacco cessation interventions in populations of pregnant women who are nicotine dependent and use alcohol and/or other psychoactive substances.

METHODS AND ANALYSIS

The review will undertake literature searches in MEDLINE, PsycINFO, CINAHL, EMBASE and ProQuest databases, as well as the grey literature. Studies of any design methodology will be included if they describe changes to tobacco smoking behaviours in quantitative terms. No restriction on year of publication or published language will apply. Participants include pregnant women of any age, who smoke tobacco, who are seeking or having treatment, or in post-treatment recovery for the use of psychoactive substances. Interventions are any psychological, behavioural or pharmacological treatments used to treat tobacco use. Outcome measures are any that quantitatively report abstinence or reductions in participant tobacco consumption. Key details and tobacco-related outcomes from included studies will be extracted and tabulated before being narratively synthesised. The systematic review protocol has been developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines.

ETHICS AND DISSEMINATION

Ethics approval is not required. Findings will be disseminated via peer-reviewed literature, conference presentations, media and social media.

PROSPERO REGISTRATION NUMBER

CRD42018108777.

Chronic Nicotine Exposure Alters the Neurophysiology of Habenulo-Interpeduncular Circuitry

Antagonism of nicotinic acetylcholine receptors (nAChRs) in the medial habenula (MHb) or interpeduncular nucleus (IPN) triggers withdrawal-like behaviors in mice chronically exposed to nicotine, implying that nicotine dependence involves the sensitization of nicotinic signaling. Identification of receptor and/or neurophysiological mechanisms underlying this sensitization is important, as it could promote novel therapeutic strategies to reduce tobacco use. Using an approach involving photoactivatable nicotine, we previously demonstrated that chronic nicotine (cNIC) potently enhances nAChR function in dendrites of MHb neurons. However, whether cNIC modulates downstream components of the habenulo-interpeduncular (Hb-IP) circuit is unknown. In this study, cNIC-mediated changes to Hb-IP nAChR function were examined in mouse (male and female) brain slices using molecular, electrophysiological, and optical techniques. cNIC enhanced action potential firing and modified spike waveform characteristics in MHb neurons. Nicotine uncaging revealed nAChR functional enhancement by cNIC on proximal axonal membranes. Similarly, nAChR-driven glutamate release from MHb axons was enhanced by cNIC. In IPN, the target structure of MHb axons, neuronal morphology, and nAChR expression is complex, with stronger nAChR function in the rostral subnucleus [rostral IPN (IPR)]. As in MHb, cNIC induced strong upregulation of nAChR function in IPN neurons. This, coupled with cNIC-enhanced nicotine-stimulated glutamate release, was associated with stronger depolarization responses to brief (1 ms) nicotine uncaging adjacent to IPR neurons. Together, these results indicate that chronic exposure to nicotine dramatically alters nicotinic cholinergic signaling and cell excitability in Hb-IP circuits, a key pathway involved in nicotine dependence.SIGNIFICANCE STATEMENT This study uncovers several neuropharmacological alterations following chronic exposure to nicotine in a key brain circuit involved in nicotine dependence. These results suggest that smokers or regular users of electronic nicotine delivery systems (i.e., "e-cigarettes") likely undergo sensitization of cholinergic circuitry in the Hb-IP system. Reducing the activity of Hb-IP nAChRs, either volitionally during smoking cessation or inadvertently via receptor desensitization during nicotine intake, may be a key trigger of withdrawal in nicotine dependence. Escalation of nicotine intake in smokers, or tolerance, may involve stimulation of these sensitized cholinergic pathways. Smoking cessation therapeutics are only marginally effective, and by identifying cellular/receptor mechanisms of nicotine dependence, our results take a step toward improved therapeutic approaches for this disorder.

[The roles of habenula and related neural circuits in neuropsychiatric diseases]

The habenula is a small and bilateral nucleus above dorsal thalamus, which contains several different types of neurons. The habenula has extensive connections with the forebrain, septum and monoaminergic nuclei in the midbrain and brainstem. Habenula is known as an 'anti-reward' nucleus, which can be activated by aversive stimulus and negative reward prediction errors. Accumulating researchs have implicated that the habenula is involved in several behaviors crucial to survival. Meanwhile, the roles of the habenula in neuropsychiatric diseases have received increasing attention. This review summaries the studies regarding the roles of habenula and the related circuits in neuropathic pain, depression, drug addiction and schizophrenia, and discusses the possibility to use the habenula as a treatment target.

Genetic correlations between nicotine reinforcement-related behaviors and propensity toward high or low alcohol preference in two replicate mouse lines

Common genetic factors may contribute to the high comorbidity between tobacco smoking and alcohol use disorder. Here, we assessed behavioral and biological effects of nicotine in replicate mouse lines selectively bred for high (HAP2/3) or low alcohol preference (LAP2/3). In Experiment 1, free-choice (FC) oral nicotine and quinine intake were assessed in HAP2/3 and LAP2/3 mice. Effects of nicotinic acetylcholine receptor blockade by mecamylamine on nicotine intake in HAP2 mice were also examined. In Experiment 2, HAP2/3 and LAP2/3 mice were tested for differences in sensitivity to nicotine-induced taste conditioning. In Experiment 3, the effects of a single nicotine injection on nucleus accumbens (NAc) and dorsal striatum monoamine levels in HAP2/3 and LAP2/3 mice were tested. In Experiment 1, HAP2/3 mice showed greater nicotine intake and intake ratio than LAP2/3 mice. There were no line differences in quinine intake. Mecamylamine reduced nicotine intake and intake ratio in HAP2 mice. In Experiment 2, HAP2/3 mice showed weaker nicotine-induced conditioned taste aversion (CTA) compared with LAP2/3 mice. In Experiment 3, nicotine treatment increased NAc dopamine turnover across both HAP2/3 and LAP2/3 mouse lines. These results show that there is a positive genetic correlation between oral alcohol intake (high alcohol intake/preference selection phenotype) and oral nicotine intake and a negative genetic correlation between oral alcohol intake and sensitivity to nicotine-induced CTA.

Systemic blockade of LPA1/3 lysophosphatidic acid receptors by ki16425 modulates the effects of ethanol on the brain and behavior

The systemic administration of lysophosphatidic acid (LPA) LPA_1/3 receptor antagonists is a promising clinical tool for cancer, sclerosis and fibrosis-related diseases. Since LPA₁ receptor-null mice engage in increased ethanol consumption, we evaluated the effects of systemic administration of an LPA_1/3 receptor antagonist (intraperitoneal ki16425, 20 mg/kg) on ethanol-related behaviors as well as on brain and plasma correlates. Acute administration of ki16425 reduced motivation for ethanol but not for saccharine in ethanol self-administering Wistar rats. Mouse experiments were conducted in two different strains. In Swiss mice, ki16425 treatment reduced both ethanol-induced sedation (loss of righting reflex, LORR) and ethanol reward (escalation in ethanol consumption and ethanol-induced conditioned place preference, CPP). Furthermore, in the CPP-trained Swiss mice, ki16425 prevented the effects of ethanol on basal c-Fos expression in the medial prefrontal cortex and on adult neurogenesis in the hippocampus. In the c57BL6/J mouse strain, however, no effects of ki16425 on LORR or voluntary drinking were observed. The c57BL6/J mouse strain was then evaluated for ethanol withdrawal symptoms, which were attenuated when ethanol was preceded by ki16425 administration. In these animals, ki16425 modulated the expression of glutamate-related genes in brain limbic regions after ethanol exposure; and peripheral LPA signaling was dysregulated by either ki16425 or ethanol. Overall, these results suggest that LPA_1/3 receptor antagonists might be a potential new class of drugs that are suitable for treating or preventing alcohol use disorders. A pharmacokinetic study revealed that systemic ki16425 showed poor brain penetration, suggesting the involvement of peripheral events to explain its effects.

The medial habenula and interpeduncular nucleus circuitry is critical in addiction, anxiety, and mood regulation

Abstinence from chronic use of addictive drugs triggers an aversive withdrawal syndrome that compels relapse and deters abstinence. Many features of this syndrome are common across multiple drugs, involving both affective and physical symptoms. Some of the network signaling underlying withdrawal symptoms overlaps with activity that is associated with aversive mood states, including anxiety and depression. Given these shared features, it is not surprising that a particular circuit, the dorsal diencephalic conduction system, and the medial habenula (MHb) and interpeduncular nucleus (IPN), in particular, have been identified as critical to the emergence of aversive states that arise both as a result and, independently, of drug addiction. As the features of this circuit continue to be characterized, the MHb-IPN axis is emerging as a viable target for therapeutics to aid in the treatment of addiction to multiple drugs of abuse as well as mood-associated disorders. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

No evidence of a role of the β4 subunit of the nicotinic acetylcholine receptor in alcohol-related behaviors

Background

Nicotinic acetylcholine receptors have gained attention in the last several years as mediators of alcohol-related behaviors. The genes that code for the α5, α3, and β4 subunits (Chrna5, Chrna3, and Chrnb4, respectively) map adjacent to each other on human chromosome 15/mouse chromosome 9. Genetic variants in this region have been associated with alcohol phenotypes and mice that overexpress these three subunits have reduced ethanol intake. In the present experiments, we examined the role of the Chrnb4 gene in three ethanol behaviors: consumption, ataxia, and sedation. Wildtype, heterozygous, and knockout mice were tested for ethanol consumption with a 2-bottle choice procedure and the drinking-in-the-dark paradigm. Ethanol-induced ataxia was measured with the balance beam and dowel test. Finally, the sedative effects of ethanol were measured with the loss of righting reflex paradigm.

Results

We observed no significant genotypic effects on any of the ethanol behaviors examined, suggesting that the β4 subunit is not involved in mediating these responses.

Conclusions

While we found no evidence for the involvement of the β4 subunit in ethanol responses, it is possible that this subunit modulates other behaviors not tested and further work should address this before completely ruling out its involvement.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2470-7) contains supplementary material, which is available to authorized users.

Recovery from alcohol dependence: Do smoking indicators predict abstinence?

BACKGROUND AND OBJECTIVES

There is inconsistent evidence about the potential influence of smoking on recovery from alcohol dependence. Our study aimed at assessing the impact of smoking-behavior on relapse during a 12 months follow-up period following a detoxification in patients with Alcohol Use Disorder (AUD).

METHODS

Three hundred Patients with AUD (74.9% smoking) were recruited from two inpatient detoxification units in psychiatric hospitals in Germany and their alcohol consumption was prospectively followed for 1 year. Data on different indicators of smoking behavior was gathered. Cox regression model was used to evaluate potential risk factors on time to relapse of alcohol consumption. Two hundred seventy-nine participants (n = 279) were included in the final analysis.

RESULTS

Smoking increased the risk for alcohol relapse (hazard ratio = 3.962, 95% CI 1.582-9.921). However, this increased risk is slightly reduced with higher numbers of daily consumed cigarettes (hazard ratio per cigarette = .986, 95% CI .976-.995).

CONCLUSION

Smoking reduced the probability of maintaining alcohol abstinence significantly, whereas higher number of cigarettes smoked daily diminished the increased risk of alcohol relapse in alcohol-dependent patients.

SCIENTIFIC SIGNIFICANCE

Coordinated psychiatric and substance abuse interventions for different subgroups of patients with AUD in the post-acute treatment phase are necessary. Individualized treatment planning is especially important in smoking patients with AUD who are vulnerable for a relapse to alcohol drinking and for somatic complications. Our findings might support individualized treatment plans. (Am J Addict 2017;26:366-373).

Alcohol and nicotine codependence-associated DNA methylation changes in promoter regions of addiction-related genes

Altered DNA methylation in addiction-related genes may modify the susceptibility to alcohol or drug dependence (AD or ND). We profiled peripheral blood DNA methylation levels of 384 CpGs in promoter regions of 82 addiction-related genes in 256 African Americans (AAs) (117 cases with AD-ND codependence and 139 controls) and 196 European Americans (103 cases with AD-ND codependence and 93 controls) using Illumina's GoldenGate DNA methylation array assays. AD-ND codependence-associated DNA methylation changes were analyzed using linear mixed-effects models with consideration of batch effects and covariates age, sex, and ancestry proportions. Seventy CpGs (in 41 genes) showed nominally significant associations (P < 0.05) with AD-ND codependence in both AAs and EAs. One CpG (HTR2B cg27531267) was hypomethylated in AA cases (P = 7.2 × 10^-5), while 17 CpGs in 16 genes (including HTR2B cg27531267) were hypermethylated in EA cases (5.6 × 10^-9 ≤ P ≤ 9.5 × 10^-5). Nevertheless, 13 single nucleotide polymorphisms (SNPs) nearby HTR2B cg27531267 and the interaction of these SNPs and cg27531267 did not show significant effects on AD-ND codependence in either AAs or EAs. Our study demonstrated that DNA methylation changes in addiction-related genes could be potential biomarkers for AD-ND co-dependence. Future studies need to explore whether DNA methylation alterations influence the risk of AD-ND codependence or the other way around.

Alcohol and nicotine interactions: pre-clinical models of dependence

While the co-morbidity of alcohol (ethanol) and tobacco (nicotine) dependence is well described, the processes that underpin this strong connection are still under debate. With the increasing popularity of electronic cigarettes (e-cigarettes), it is now becoming more important to look to the neurobiological mechanisms involving alcohol and nicotine interactions to effectively treat a new generation of co-dependent individuals. Researchers have already recognized that the neuropathology produced by the combination of nicotine and ethanol is likely to produce an addictive nature very different to that of either one alone, and are employing a mixture of pre-clinical techniques to establish and investigate every stage in the development of both nicotine and ethanol-seeking behaviors. While it is agreed that multiple pathways orchestrate the complex reward profile of alcohol and nicotine co-addiction, several lines of evidence suggest the convergent site of action is within the mesolimbic dopaminergic system, at neuronal nicotinic acetylcholine receptors (nAChRs). A whole host of strategies are currently being employed to discover and unravel previously unknown or ill understood neurobiological processes in the brain, contributing greatly toward the development of novel pharmacotherapies with the aim of improving patient outcomes. This review intends to shed some light on the most influential and most recent pre-clinical work that is leading the charge in modeling this complicated relationship.

Interactions between nicotine and drugs of abuse: a review of preclinical findings

Polysubstance abuse is common among substance-use disorder patients, and nicotine is one of the most commonly co-used substances. Epidemiological and clinical laboratory studies suggest that nicotine, when combined with other drugs of abuse, increases intake of one or both substances. This review focuses on the preclinical literature regarding nicotine's interaction with alcohol, stimulants (i.e., cocaine, amphetamines), opioids (i.e., morphine, heroin), and Δ⁹-tetrahydrocannabinol (THC). The current understanding of how these various classes of abused drugs may interact with nicotine on behavioral, physiological, and pharmacological indices that may be important in maintaining co-use of one or both substances in human populations are highlighted. Suggestions as to future areas of research and gaps in knowledge are offered.

Mechanisms and genetic factors underlying co-use of nicotine and alcohol or other drugs of abuse

Concurrent use of tobacco and alcohol or psychostimulants represents a major public health concern, with use of one substance influencing consumption of the other. Co-abuse of these drugs leads to substantial negative health outcomes, reduced cessation, and high economic costs, but the underlying mechanisms are poorly understood. Epidemiological data suggest that tobacco use during adolescence plays a particularly significant role. Adolescence is a sensitive period of development marked by major neurobiological maturation of brain regions critical for reward processing, learning and memory, and executive function. Nicotine exposure during this time produces a unique and long-lasting vulnerability to subsequent substance use, likely via actions at cholinergic, dopaminergic, and serotonergic systems. In this review, we discuss recent clinical and preclinical data examining the genetic factors and mechanisms underlying co-use of nicotine and alcohol or cocaine and amphetamines. We evaluate the critical role of nicotinic acetylcholine receptors throughout, and emphasize the dearth of preclinical studies assessing concurrent drug exposure. We stress important age and sex differences in drug responses, and highlight a brief, low-dose nicotine exposure paradigm that may better model early use of tobacco products. The escalating use of e-cigarettes among youth necessitates a closer look at the consequences of early adolescent nicotine exposure on subsequent alcohol and drug abuse.

Voluntary co-consumption of alcohol and nicotine: Effects of abstinence, intermittency, and withdrawal in mice

Alcohol and nicotine are often used together, and there is a high rate of co-occurrence between alcohol and nicotine addiction. Most animal models studying alcohol and nicotine interactions have utilized passive drug administration, which may not be relevant to human co-addiction. In addition, the interactions between alcohol and nicotine in female animals have been understudied, as most studies have used male animals. To address these issues, we developed models of alcohol and nicotine co-consumption in male and female mice that utilized voluntary, oral consumption of unsweetened alcohol, nicotine and water. We first examined drug consumption and preference in single-drug, sequential alcohol and nicotine consumption tests in male and female C57BL/6 and DBA/2J mice. We then tested chronic continuous and intermittent access alcohol and nicotine co-consumption procedures. We found that male and female C57BL/6 mice readily co-consumed unsweetened alcohol and nicotine. In our continuous co-consumption procedures, we found that varying the available nicotine concentration during an alcohol abstinence period affected compensatory nicotine consumption during alcohol abstinence, and affected rebound alcohol consumption when alcohol was re-introduced. Consumption of alcohol and nicotine in an intermittent co-consumption procedure produced higher alcohol consumption levels, but not nicotine consumption levels, compared with the continuous co-consumption procedures. Finally, we found that intermittent alcohol and nicotine co-consumption resulted in physical dependence. Our data show that these voluntary co-consumption procedures can be easily performed in mice and can be used to study behavioral interactions between alcohol and nicotine consumption, which may better model human alcohol and nicotine co-addiction.

How Imaging Glutamate, γ-Aminobutyric Acid, and Dopamine Can Inform the Clinical Treatment of Alcohol Dependence and Withdrawal

Neuroimaging studies have dramatically advanced our understanding of the neurochemical basis of alcohol dependence, a major public health issue. In this paper, we review the research generated from neurochemical specific imaging modalities including magnetic resonance spectroscopy, positron emission tomography, and single-photon emission computed tomography in studies of alcohol dependence and withdrawal. We focus on studies interrogating γ-aminobutyric acid (GABA), glutamate, and dopamine, as these are prominent neurotransmitter systems implicated in alcohol dependence. Highlighted findings include diminished dopaminergic functioning and modulation of the GABA system by tobacco smoking during alcohol withdrawal. Then, we consider how these findings impact the clinical treatment of alcohol dependence and discuss directions for future experiments to address existing gaps in the literature, for example, sex differences and smoking comorbidity. These and other considerations provide opportunities to build upon the current neurochemistry imaging literature of alcohol dependence and withdrawal, which may usher in improved therapeutic and relapse prevention strategies.