Alcohol and the Brain: Neuronal Molecular Targets, Synapses, and Circuits

Ethanol-induced locomotor sensitization: Neuronal activation in the nucleus accumbens and medial prefrontal cortex

Ethanol consumption may promote neuroplasticity and alterations in synapses, resulting in modifications in neuronal activity. Here, we treated male Swiss mice with ethanol (2.2 g/kg) or saline once per day for 21 consecutive days. Nine days after the last ethanol administration, they received a challenge injection of ethanol or saline, and we assessed locomotor activity. After the behavioral analysis, we evaluated neuronal activation in the medial Prefrontal Cortex (Cingulate, Prelimbic, and Infralimbic) and the Nucleus Accumbens (Shell and Core) using Fos/DAB immunohistochemistry. In another group of animals, we performed the quantitative analysis of the ARC and PSD-95 protein levels by Western blotting in the medial prefrontal cortex and nucleus accumbens brain areas. Repeated ethanol administration produced locomotor sensitization, accompanied by an increase in the nucleus accumbens shell's activation but not core. Furthermore, the ethanol pretreatment reduced ARC expression in the nucleus accumbens and medial prefrontal cortex. Our results suggest the participation of the nucleus accumbens shell in ethanol behavioral sensitization and add new pieces of evidence that neuroplasticity in synapses may contribute to the mechanism underlying this behavior.

Ethanol induces persistent potentiation of 5-HT3 receptor-stimulated GABA release at synapses on rat hippocampal CA1 neurons

Several studies have shown that ethanol (EtOH) can enhance the activity of GABAergic synapses via presynaptic mechanisms, including in hippocampal CA1 neurons. The serotonin type 3 receptor (5-HT3-R) has been implicated in the neural actions of ethanol (EtOH) and in modulation of GABA release from presynaptic terminals. In the present study, we investigated EtOH modulation of GABA release induced by 5-HT3-R activation using the mechanically isolated neuron/bouton preparation from the rat CA1 hippocampal subregion. EtOH application before and during exposure to the selective 5-HT3 receptor agonist, m-chlorophenylbiguanide (mCPBG) potentiated the mCPBG-induced increases in the peak frequency and charge transfer of spontaneous GABAergic inhibitory postsynaptic currents. Interestingly, the potentiation was maintained even after EtOH was removed from the preparation. A protein kinase A inhibitor reduced the magnitude of EtOH potentiation. Fluorescent Ca2+ imaging showed that Ca2+ transients in the presynaptic terminals increased during EtOH exposure. These findings indicate that EtOH produces long-lasting potentiation of 5-HT3-induced GABA release by modulating calcium levels, via a process involving cAMP-mediated signaling in presynaptic terminals.

Voluntary intake of psychoactive substances is regulated by the dopamine receptor Dop1R1 in Drosophila

Dysregulated motivation to consume psychoactive substances leads to addictive behaviors that often result in serious health consequences. Understanding the neuronal mechanisms that drive drug consumption is crucial for developing new therapeutic strategies. The fruit fly Drosophila melanogaster offers a unique opportunity to approach this problem with a battery of sophisticated neurogenetic tools available, but how they consume these drugs remains largely unknown. Here, we examined drug self-administration behavior of Drosophila and the underlying neuronal mechanisms. We measured the preference of flies for five different psychoactive substances using a two-choice feeding assay and monitored its long-term changes. We found that flies show acute preference for ethanol and methamphetamine, but not for cocaine, caffeine or morphine. Repeated intake of ethanol, but not methamphetamine, increased over time. Preference for methamphetamine and the long-term escalation of ethanol preference required the dopamine receptor Dop1R1 in the mushroom body. The protein level of Dop1R1 increased after repeated intake of ethanol, but not methamphetamine, which correlates with the acquired preference. Genetic overexpression of Dop1R1 enhanced ethanol preference. These results reveal a striking diversity of response to individual drugs in the fly and the role of dopamine signaling and its plastic changes in controlling voluntary intake of drugs.

Alcohol use and mental health during COVID-19 lockdown: A cross-sectional study in a sample of UK adults

BACKGROUND

The aim was to examine the correlates of increased alcohol consumption during the COVID-19 pandemic-related restrictions that were implemented in a sample of UK adults.

METHODS

This paper presents analyses of data from a cross-sectional study. Adults aged 18 years and over, residing in the UK and self-isolating from others outside their own household were eligible to participate. Participants reported increase or no increase in their level of alcohol consumption from before to during lockdown, as well as symptoms of anxiety, depression and mental wellbeing. Socio-demographic characteristics were compared between adults with and without reported increased alcohol consumption. The associations between reported increased alcohol consumption and mental health outcomes were investigated using logistic and linear regression analyses.

RESULTS

691 adults (61.1 % women; 48.8 % aged 35-64 years) were included in the analysis. Of these, 17 % reported increased alcohol consumption after lockdown. A higher proportion of 18-34-year olds reported increased alcohol consumption compared to older groups. The prevalence of poor overall mental health was significantly higher in individuals with increased alcohol consumption (vs. no increase) (45.4 % versus 32.7 %; p-value = 0.01). There was a significant association between increased alcohol consumption and poor overall mental health (OR = 1.64; 95 % CI = 1.01, 2.66), depressive symptoms (unstandardized beta = 2.93; 95 % CI = 0.91, 4.95) and mental wellbeing (unstandardized beta=-1.38; 95 % CI=-2.38, -0.39).

CONCLUSIONS

More than one in six UK adults increased their alcohol consumption during lockdown and a higher proportion of these were younger adults. Increased alcohol consumption was independently associated with poor overall mental health, increased depressive symptoms and lower mental wellbeing. These findings highlight the importance of planning targeted support as we emerge from lockdown and plan for potential second and subsequent waves.

A deeper insight into how GABA-B receptor agonism via baclofen may affect alcohol seeking and consumption: lessons learned from a human laboratory investigation

Previous studies suggest that GABA-B receptor agonism may represent an effective pharmacological approach to treat addictive disorders. Baclofen is a selective GABA-B receptor agonist which has been investigated as a potential treatment for alcohol use disorder. However, research is needed to understand the biobehavioral mechanisms underlying baclofen's effect on alcohol use. In the present randomized, double-blind, placebo-controlled study, thirty-four alcohol-dependent individuals were randomized to receive baclofen (30 mg/d) or placebo for a week, and then participated in a laboratory experiment consisting of three procedures: alcohol cue-reactivity, priming, and self-administration. During the experiment, craving and other subjective responses to alcohol were assessed, and blood samples were collected for pharmacokinetic measurements. The effects of baclofen on the relationships between different alcohol-related laboratory parameters were investigated. Baclofen pharmacokinetic parameters and their correlations with behavioral measures were also examined. Results showed that baclofen disrupted the link between alcohol priming and self-administration, as indicated by significant interaction effects between drug condition (baclofen vs. placebo) and some of the priming variables (alcohol craving: F_3,9 = 6.03, p = 0.01; alcohol sedation: F_3,6 = 7.16, p = 0.01) on the total amount of alcohol self-administered. Considerable interindividual variability in baclofen pharmacokinetic parameters was observed. Maximum plasma concentrations of baclofen negatively correlated with cue-induced alcohol craving (r = -0.57, p = 0.03) and priming-induced ratings of 'like more' (r = -0.59, p = 0.02). In conclusion, baclofen may work by dissociating the link between an initial drink (priming) and subsequent alcohol consumption (self-administration). Considerable pharmacokinetic variability is an important factor to take into account when employing baclofen as a treatment for alcohol use disorder.

A neuroactive steroid with a therapeutically interesting constellation of actions at GABAA and NMDA receptors

Neuroactive steroids are an ascendant class of treatment for neuropsychiatric illness. Effects on ligand-gated neurotransmitter receptors appear to be a major mechanism of action. Here we describe a neuroactive steroid with a unique constellation of receptor actions. MQ-221 is a sulfated, 3β-hydroxy neurosteroid analogue that inhibits NMDAR function but also potentiates GABAAR function, thereby exhibiting unusual but potentially clinically desirable effects. Although the compound also exhibited features of other sulfated steroids, namely activation-dependent inhibition of GABAAR function, net potentiation dominated under physiological conditions. Potentiation of GABAAR function was distinct from the mechanism governing potentiation by anesthetic neurosteroids. Inhibition of NMDAR function showed weaker channel activation dependence than pregnanolone sulfate (3α5βPS). MQ-221 was unique among four stereoisomers explored in the pattern of effects at GABAA and NMDARs. Taken together, MQ-221 may represent a new class of compound with unique psychoactive effects and beneficial prospects for treating neuropsychiatric disorders.

Advances in Targeting GIRK Channels in Disease

G protein-gated inwardly rectifying potassium (GIRK) channels are essential regulators of cell excitability in the brain. While they are implicated in a variety of neurological diseases in both human and animal model studies, their therapeutic potential has been largely untapped. Here, we review recent advances in the development of small molecule compounds that specifically modulate GIRK channels and compare them with first-generation compounds that exhibit off-target activity. We describe the method of discovery of these small molecule modulators, their chemical features, and their effects in vivo. These studies provide a promising outlook on the future development of subunit-specific GIRK modulators to regulate neuronal excitability in a brain region-specific manner.

Oxysterols Modulate the Acute Effects of Ethanol on Hippocampal N-Methyl-d-Aspartate Receptors, Long-Term Potentiation, and Learning

Ethanol is a noncompetitive inhibitor of N-methyl-d-aspartate receptors (NMDARs) and acutely disrupts hippocampal synaptic plasticity and learning. In the present study, we examined the effects of oxysterol positive allosteric modulators (PAMs) of NMDARs on ethanol-mediated inhibition of NMDARs, block of long-term potentiation (LTP) and long-term depression (LTD) in rat hippocampal slices, and defects in one-trial learning in vivo. We found that 24S-hydroxycholesterol and a synthetic oxysterol analog, SGE-301, overcame effects of ethanol on NMDAR-mediated synaptic responses in the CA1 region but did not alter acute effects of ethanol on LTD; the synthetic oxysterol, however, overcame acute inhibition of LTP. In addition, both oxysterols overcame persistent effects of ethanol on LTP in vitro, and the synthetic analog reversed defects in one-trial inhibitory avoidance learning in vivo. These results indicate that effects of ethanol on both LTP and LTD arise by complex mechanisms beyond NMDAR antagonism and that oxysterol NMDAR PAMS may represent a novel approach for preventing and reversing acute ethanol-mediated changes in cognition.

Nicotine, cocaine, amphetamine, morphine, and ethanol increase norepinephrine output in the bed nucleus of stria terminalis of freely moving rats

The bed nucleus of stria terminalis (BNST) is a complex limbic area involved in neuroendocrine and behavioural responses and, in particular, in the modulation of the stress response. BNST is innervated by dopamine and norepinephrine, which are known to be involved in drug addiction. It is also known that several drugs of abuse increase dopamine transmission in the BNST, but there has been less research regarding the effect on norepinephrine transmission. Here, we have used the microdialysis technique to investigate the effect of several drugs of abuse on norepinephrine transmission in the BNST of freely moving rats. We observed that nicotine (0.2-0.4 mg/kg), cocaine (2.5-5 mg/kg), amphetamine (0.25-0.5 mg/kg), and ethanol (0.5-1.0 g/kg), dose-dependently increased norepinephrine output while the effect of morphine at 3.0 was lower than that of 1.0 mg/kg. These results suggest that many drugs of abuse, though possessing diverse mechanisms of action, share the property of increasing norepinephrine transmission in the BNST. Furthermore, we suggest that the recurring activation of NE transmission in the BNST, due to drug administration, contributes to the alteration of the function that BNST assumes in how the behavioural response to stress manifests, favouring the establishment of the stress-induced drug seeking.

Neurodevelopmental signatures of narcotic and neuropsychiatric risk factors in 3D human-derived forebrain organoids

It is widely accepted that narcotic use during pregnancy and specific environmental factors (e.g., maternal immune activation and chronic stress) may increase risk of neuropsychiatric illness in offspring. However, little progress has been made in defining human-specific in utero neurodevelopmental pathology due to ethical and technical challenges associated with accessing human prenatal brain tissue. Here we utilized human induced pluripotent stem cells (hiPSCs) to generate reproducible organoids that recapitulate dorsal forebrain development including early corticogenesis. We systemically exposed organoid samples to chemically defined "enviromimetic" compounds to examine the developmental effects of various narcotic and neuropsychiatric-related risk factors within tissue of human origin. In tandem experiments conducted in parallel, we modeled exposure to opiates (μ-opioid agonist endomorphin), cannabinoids (WIN 55,212-2), alcohol (ethanol), smoking (nicotine), chronic stress (human cortisol), and maternal immune activation (human Interleukin-17a; IL17a). Human-derived dorsal forebrain organoids were consequently analyzed via an array of unbiased and high-throughput analytical approaches, including state-of-the-art TMT-16plex liquid chromatography/mass-spectrometry (LC/MS) proteomics, hybrid MS metabolomics, and flow cytometry panels to determine cell-cycle dynamics and rates of cell death. This pipeline subsequently revealed both common and unique proteome, reactome, and metabolome alterations as a consequence of enviromimetic modeling of narcotic use and neuropsychiatric-related risk factors in tissue of human origin. However, of our 6 treatment groups, human-derived organoids treated with the cannabinoid agonist WIN 55,212-2 exhibited the least convergence of all groups. Single-cell analysis revealed that WIN 55,212-2 increased DNA fragmentation, an indicator of apoptosis, in human-derived dorsal forebrain organoids. We subsequently confirmed induction of DNA damage and apoptosis by WIN 55,212-2 within 3D human-derived dorsal forebrain organoids. Lastly, in a BrdU pulse-chase neocortical neurogenesis paradigm, we identified that WIN 55,212-2 was the only enviromimetic treatment to disrupt newborn neuron numbers within human-derived dorsal forebrain organoids. Cumulatively this study serves as both a resource and foundation from which human 3D biologics can be used to resolve the non-genomic effects of neuropsychiatric risk factors under controlled laboratory conditions. While synthetic cannabinoids can differ from naturally occurring compounds in their effects, our data nonetheless suggests that exposure to WIN 55,212-2 elicits neurotoxicity within human-derived developing forebrain tissue. These human-derived data therefore support the long-standing belief that maternal use of cannabinoids may require caution so to avoid any potential neurodevelopmental effects upon developing offspring in utero.

Acute Ethanol Exposure Enhances Synaptic Plasticity in the Dorsal Striatum in Adult Male and Female Rats

Background:

Acute (ex vivo) and chronic (in vivo) alcohol exposure induces neuroplastic changes in the dorsal striatum, a critical region implicated in instrumental learning.

Objective:

Sex differences are evident in alcohol reward and reinforcement, with female rats consuming higher amount of alcohol in operant paradigms compared to male rats. However, sex differences in the neuroplastic changes produced by acute alcohol in the dorsal striatum have been unexplored.

Methods:

Using electrophysiological recordings from dorsal striatal slices obtained from adult male and female rats, we investigated the effects of ex vivo ethanol exposure on synaptic transmission and synaptic plasticity. Ethanol (44 mM) enhanced basal synaptic transmission in both sexes. Ethanol also enhanced long-term potentiation in both sexes. Other measures of synaptic plasticity including paired-pulse ratio were unaltered by ethanol in both sexes.

Results:

The results suggest that alterations in synaptic plasticity induced by acute ethanol, at a concentration associated with intoxication, could play an important role in alcohol-induced experience-dependent modification of corticostriatal circuits underlying the learning of goal-directed instrumental actions and formation of habits mediating alcohol seeking and taking.

Conclusions:

Taken together, understanding the mechanism(s) underlying alcohol induced changes in corticostriatal function may lead to the development of more effective therapeutic agents to reduce habitual drinking and seeking associated with alcohol use disorders.

Tumour Necrosis Factor in Neuroplasticity, Neurogenesis and Alcohol Use Disorder

Alcohol use disorder is a pervasive and detrimental condition that involves changes in neuroplasticity and neurogenesis. Alcohol activates the neuroimmune system and alters the inflammatory status of the brain. Tumour necrosis factor (TNF) is a well characterised neuroimmune signal but its involvement in alcohol use disorder is unknown. In this review, we discuss the variable findings of TNF's effect on neuroplasticity and neurogenesis. Acute ethanol exposure reduces TNF release while chronic alcohol intake generally increases TNF levels. Evidence suggests TNF potentiates excitatory transmission, promotes anxiety during alcohol withdrawal and is involved in drug use in rodents. An association between craving for alcohol and TNF is apparent during withdrawal in humans. While anti-inflammatory therapies show efficacy in reversing neurogenic deficit after alcohol exposure, there is no evidence for TNF's essential involvement in alcohol's effect on neurogenesis. Overall, defining TNF's role in alcohol use disorder is complicated by poor understanding of its variable effects on synaptic transmission and neurogenesis. While TNF may be of relevance during withdrawal, the neuroimmune system likely acts through a larger group of inflammatory cytokines to alter neuroplasticity and neurogenesis. Understanding the individual relevance of TNF in alcohol use disorder awaits a more comprehensive understanding of TNF's effects within the brain.

Electroencephalographic signatures of the binge drinking pattern during adolescence and young adulthood: A PRISMA-driven systematic review

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Controls and binge drinkers (BDs) do not differ in their behavioral performance.

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BDs show increased neural activity during attention, working memory and inhibition.

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Augmented P3 amplitude in BDs was the most solid electrophysiological finding.

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Evidence does not support specific gender vulnerabilities to the effects of BD.

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Memory, emotional processing and decision-making processes need further exploration.

Research on neurophysiological impairments associated with binge drinking (BD), an excessive but episodic alcohol use pattern, has significantly increased over the last decade. This work is the first to systematically review –following PRISMA guidelines- the empirical evidence regarding the effects of BD on neural activity –assessed by electroencephalography- of adolescents and young adults. A systematic review was conducted in 34 studies (N = 1723). Results indicated that binge drinkers (BDs) showed similar behavioral performance as non/low drinkers. The most solid electrophysiological finding was an augmented P3 amplitude during attention, working memory and inhibition tasks. This increased neural activity suggests the recruitment of additional resources to perform the task at adequate/successful levels, which supports the neurocompensation hypothesis. Similar to alcoholics, BDs also displayed increased reactivity to alcohol-related cues, augmented resting-state electrophysiological signal and reduced activity during error detection –which gives support to the continuum hypothesis. Evidence does not seem to support greater vulnerability to BD in females. Replication and longitudinal studies are required to account for mixed results and to elucidate the extent/direction of the neural impairments associated with BD.

Acetylcholine Muscarinic M4 Receptors as a Therapeutic Target for Alcohol Use Disorder: Converging Evidence From Humans and Rodents

BACKGROUND

Alcohol use disorder (AUD) is a major socioeconomic burden on society, and current pharmacotherapeutic treatment options are inadequate. Aberrant alcohol use and seeking alters frontostriatal function.

METHODS

We performed genome-wide RNA sequencing and subsequent quantitative polymerase chain reaction and receptor binding validation in the caudate-putamen of human AUD samples to identify potential therapeutic targets. We then back-translated our top candidate targets into a rodent model of long-term alcohol consumption to assess concordance of molecular adaptations in the rat striatum. Finally, we adopted rat behavioral models of alcohol intake and seeking to validate a potential therapeutic target.

RESULTS

We found that G protein-coupled receptors were the top canonical pathway differentially regulated in individuals with AUD. The M₄ muscarinic acetylcholine receptor (mAChR) was downregulated at the gene and protein levels in the putamen, but not in the caudate, of AUD samples. We found concordant downregulation of the M₄ mAChR, specifically on dopamine D₁ receptor-expressing medium spiny neurons in the rat dorsolateral striatum. Systemic administration of the selective M₄ mAChR positive allosteric modulator, VU0467154, reduced home cage and operant alcohol self-administration, motivation to obtain alcohol, and cue-induced reinstatement of alcohol seeking in rats. Local microinjections of VU0467154 in the rat dorsolateral striatum reduced alcohol self-administration and cue-induced reinstatement of alcohol seeking.

CONCLUSIONS

Collectively, these results identify the M₄ mAChR as a potential therapeutic target for the treatment of AUD and the D₁ receptor-positive medium spiny neurons in the dorsolateral striatum as a key site mediating the actions of M₄ mAChR in relation to alcohol consumption and seeking.

The Neurotransmitters Involved in Drosophila Alcohol-Induced Behaviors

Alcohol is a widely used and abused substance with numerous negative consequences for human health and safety. Historically, alcohol's widespread, non-specific neurobiological effects have made it a challenge to study in humans. Therefore, model organisms are a critical tool for unraveling the mechanisms of alcohol action and subsequent effects on behavior. Drosophila melanogaster is genetically tractable and displays a vast behavioral repertoire, making it a particularly good candidate for examining the neurobiology of alcohol responses. In addition to being experimentally amenable, Drosophila have high face and mechanistic validity: their alcohol-related behaviors are remarkably consistent with humans and other mammalian species, and they share numerous conserved neurotransmitters and signaling pathways. Flies have a long history in alcohol research, which has been enhanced in recent years by the development of tools that allow for manipulating individual Drosophila neurotransmitters. Through advancements such as the GAL4/UAS system and CRISPR/Cas9 mutagenesis, investigation of specific neurotransmitters in small subsets of neurons has become ever more achievable. In this review, we describe recent progress in understanding the contribution of seven neurotransmitters to fly behavior, focusing on their roles in alcohol response: dopamine, octopamine, tyramine, serotonin, glutamate, GABA, and acetylcholine. We chose these small-molecule neurotransmitters due to their conservation in mammals and their importance for behavior. While neurotransmitters like dopamine and octopamine have received significant research emphasis regarding their contributions to behavior, others, like glutamate, GABA, and acetylcholine, remain relatively unexplored. Here, we summarize recent genetic and behavioral findings concerning these seven neurotransmitters and their roles in the behavioral response to alcohol, highlighting the fitness of the fly as a model for human alcohol use.

An amylin and calcitonin receptor agonist modulates alcohol behaviors by acting on reward-related areas in the brain

Alcohol causes stimulatory behavioral responses by activating reward-processing brain areas including the laterodorsal (LDTg) and ventral tegmental areas (VTA) and the nucleus accumbens (NAc). Systemic administration of the amylin and calcitonin receptor agonist salmon calcitonin (sCT) attenuates alcohol-mediated behaviors, but the brain sites involved in this process remain unknown. Firstly, to identify potential sCT sites of action in the brain, we used immunohistochemistry after systemic administration of fluorescent-labeled sCT. We then performed behavioral experiments to explore how infused sCT into the aforementioned reward-processing brain areas affects acute alcohol-induced behaviors in mice and chronic alcohol consumption in rats. We show that peripheral sCT crosses the blood brain barrier and is detected in all the brain areas studied herein. sCT infused into the LDTg attenuates alcohol-evoked dopamine release in the NAc shell in mice and reduces alcohol intake in rats. sCT into the VTA blocks alcohol-induced locomotor stimulation and dopamine release in the NAc shell in mice and decreases alcohol intake in rats. Lastly, sCT into the NAc shell prevents alcohol-induced locomotor activity in mice. Our data suggest that central sCT modulates the ability of alcohol to activate reward-processing brain regions.

Growth Factors and Alcohol Use Disorder

Neurotrophic growth factors were originally characterized for their support in neuronal differentiation, outgrowth, and survival during development. However, it has been acknowledged that they also play a vital role in the adult brain. Abnormalities in growth factors have been implicated in a variety of neurological and psychiatric disorders, including alcohol use disorder (AUD). This work focuses on the interaction between alcohol and growth factors. We review literature suggesting that several growth factors play a unique role in the regulation of alcohol consumption, and that breakdown in these growth factor systems is linked to the development of AUD. Specifically, we focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), and insulin growth factor 1 (IGF-1). We also review the literature on the potential role of midkine (MDK) and pleiotrophin (PTN) and their receptor, anaplastic lymphoma kinase (ALK), in AUD. We show that alcohol alters the expression of these growth factors or their receptors in brain regions previously implicated in addiction, and that manipulations on these growth factors and their downstream signaling can affect alcohol-drinking behaviors in animal models. We conclude that there is a need for translational and clinical research to assess the therapeutic potential of new pharmacotherapies targeting these systems.

Acute Effects of Ethanol on Hippocampal Spatial Representation and Offline Reactivation

Acute alcohol exposure impairs hippocampus-dependent spatial memory. However, there is little evidence for the effects of ethanol on the spike patterns of hippocampal cell populations. Here, we examined how the spatial firing patterns of place cells, neurons that encode specific locations, were altered in rats that were intraperitoneally injected with 1.5 g/kg ethanol. Ethanol administration partly reduced or abolished place-selective spiking of a subset of place cells during running periods in a spatial task, whereas a subset of place fields newly emerged, suggesting a partial reorganization of hippocampal spatial maps by ethanol. On the other hand, ethanol administration did not significantly alter the frequency of hippocampal sharp-wave ripple (SWRs) and synchronous spike patterns during resting periods, suggesting that offline memory consolidation and retrieval mechanisms underpinned by hippocampal neuronal synchronization are not strongly affected by ethanol. These results indicate that acute ethanol intake mainly affects the encoding of external information but has little impact on internal memory processing.

Identifying functionally relevant candidate genes for inflexible ethanol intake in mice and humans using a guilt-by-association approach

Gene prioritization approaches are useful tools to explore and select candidate genes in transcriptome studies. Knowing the importance of processes such as neuronal activity, intracellular signal transduction, and synapse plasticity to the development and maintenance of compulsive ethanol drinking, the aim of the present study was to explore and identify functional candidate genes associated with these processes in an animal model of inflexible pattern of ethanol intake. To do this, we applied a guilt-by-association approach, using the GUILDify and ToppGene software, in our previously published microarray data from the prefrontal cortex (PFC) and striatum of inflexible drinker mice. We then tested some of the prioritized genes that showed a tissue-specific pattern in postmortem brain tissue (PFC and nucleus accumbens (NAc)) from humans with alcohol use disorder (AUD). In the mouse brain, we prioritized 44 genes in PFC and 26 in striatum, which showed opposite regulation patterns in PFC and striatum. The most prioritized of them (i.e., Plcb1 and Prkcb in PFC, and Dnm2 and Lrrk2 in striatum) were associated with synaptic neuroplasticity, a neuroadaptation associated with excessive ethanol drinking. The identification of transcription factors among the prioritized genes suggests a crucial role for Irf4 in the pattern of regulation observed between PFC and striatum. Lastly, the differential transcription of IRF4 and LRRK2 in PFC and nucleus accumbens in postmortem brains from AUD compared to control highlights their involvement in compulsive ethanol drinking in humans and mice.

Assessment of Ethanol-Induced Toxicity on iPSC-Derived Human Neurons Using a Novel High-Throughput Mitochondrial Neuronal Health (MNH) Assay

Excessive ethanol exposure can cause mitochondrial and cellular toxicity. In order to discover potential counteracting interventions, it is essential to develop assays capable of capturing the consequences of ethanol exposure in human neurons, and particularly dopaminergic neurons that are crucial for the development of alcohol use disorders (AUD). Here, we developed a novel high-throughput (HT) assay to quantify mitochondrial and neuronal toxicity in human dopaminergic neuron-containing cultures (DNs) from induced pluripotent stem cells (iPSCs). The assay, dubbed mitochondrial neuronal health (MNH) assay, combines live-cell measurement of mitochondrial membrane potential (MMP) with quantification of neuronal branching complexity post-fixation. Using the MNH assay, we demonstrated that chronic ethanol exposure in human iPSC-derived DNs decreases MMP and neuronal outgrowth in a dose-dependent manner. The toxic effect of ethanol on DNs was already detectable after 1 h of exposure, and occurred similarly in DNs derived from healthy individuals and from patients with AUD. We next used the MNH assay to carry out a proof-of-concept compound screening using FDA-approved drugs. We identified potential candidate compounds modulating acute ethanol toxicity in human DNs. We found that disulfiram and baclofen, which are used for AUD treatment, and lithium caused neurotoxicity also in the absence of ethanol, while the spasmolytic drug flavoxate positively influenced MNH. Altogether, we developed an HT assay to probe human MNH and used it to assess ethanol neurotoxicity and to identify modulating agents. The MNH assay represents an effective new tool for discovering modulators of MNH and toxicity in live human neurons.

Chronic Alcohol Exposure Induces Aberrant Mitochondrial Morphology and Inhibits Respiratory Capacity in the Medial Prefrontal Cortex of Mice

Alcohol use disorder (AUD) is characterized as a chronic, relapsing disease with a pattern of excessive drinking despite negative consequences to an individual’s life. Severe chronic alcohol use impairs the function of the medial prefrontal cortex (mPFC), which contributes to alcohol-induced cognitive and executive dysfunction. The mPFC contains more mitochondria compared to other cortical areas, which suggests mitochondrial damage may occur in AUD and trigger subsequent behavior change. Here, we identified morphological and functional changes in mitochondria in the mPFC in C57BL6/J mice after 8 h of withdrawal from chronic intermittent alcohol (CIA) exposure. Three-dimensional serial block-face scanning electron microscopy (SBFSEM) reconstruction revealed that CIA exposure elongated mPFC mitochondria and formed mitochondria-on-a-string (MOAS). Furthermore, alcohol significantly affected mitochondrial bioenergetics, including oxidative phosphorylation and electron transport, with inhibited aerobic respiration in mPFC mitochondria after CIA exposure. We also found decreased expression of fusion (mitofusin 2, Mfn2) and increased fission (mitochondrial fission 1 protein, Fis1) proteins in the mPFC of alcohol-treated mice. In sum, our study suggests that CIA exposure impairs mitochondrial dynamics and function in the mPFC.

Pharmacological characterization of the forced swim test in Drosophila melanogaster

The forced swim test is commonly used as a preclinical screen of antidepressant medication efficacy in rats and mice. Neckameyer and Nieto-Romero (Stress 18:254-66, 2015) adopted the forced swim test for use with the fruit fly Drosophila melanogaster and showed that behavior in this test is sensitive to several physiologically relevant stressors. However, whether this test might be sensitive to the effects of antidepressant medications or other compounds is unknown. In the current studies, we fed drugs to male and female flies that we expected to either decrease or increase the duration of immobility in the forced swim test, including fluoxetine, desipramine, picrotoxin, reserpine, 3-iodo-tyrosine, and ethanol. Fluoxetine was the only drug tested that affected behavior in this test, and surprisingly, the direction of the effect depended on the duration of feeding. Short-term (30 min) feeding of the drug prior to test resulted in the expected increase in latency to immobility, while a longer feeding duration (20-24 h) decreased this measure. These results suggest that the pharmacological profile of the fly FST is more restricted than that of the rat or mouse FST, and that the duration of drug exposure is an important consideration in pharmacological research using flies.

Alcohol-related brain injury: An unrecognized problem in acute medicine

Alcohol-related brain injury (ARBI) is an unrecognized and therefore untreated consequence of alcohol use disorder. Here, we explore a 12-month period prevalence of alcohol-related brain injury (ARBI) in alcohol use disorder patients. Inpatients aged ≥18 years reviewed by the Alcohol Care Team's Specialist Nurses between April 1, 2017 and March 31, 2018 were eligible for the study (n = 1276). Screening identified a high-risk subset of patients who matched at least one of the following: 1) more than three alcohol-related admissions in one year; 2) two alcohol-related admissions in any given 30-day period; 3) patient or their significant other had concerns regarding cognition. The high-risk patients were assessed for evidence of ARBI using the Montreal Cognitive Assessment Tool (MoCA). The primary measure of interest was MoCA ≤23. Analysis was conducted between subgroups of the study population to identify prevalence rate ratios for matching the high-risk screening criteria, and MoCA ≤23 in high-risk patients. Two hundred and five patients were identified as high risk for ARBI. The period prevalence rates in this high-risk group for patients with a MoCA ≤23 was 36.1%. Those under the age of 35 years were significantly less likely to match the high-risk criteria. Patients that were homeless or staying in hostels were more likely to match the high-risk criteria and were also at increased risk of MoCA ≤23, compared with those living with family members. In summary, ARBI is common in patients with AUD attending acute hospitals. ARBI is often not diagnosed, and thus further work is required to improve screening for, and identification of, these patients to develop evidence-based clinical pathways that optimize care.

Alcohol-Induced Neuropathy in Chronic Alcoholism: Causes, Pathophysiology, Diagnosis, and Treatment Options

Purpose of the Review

Alcohol abuse causes a wide range of disorders that affect the nervous system. These include confusion, cerebellar ataxia, peripheral neuropathy, and cognitive impairment. Chronic and excessive alcohol consumption is the primary cause of peripheral neuropathy. It is worth noting that peripheral neuropathy has no reliable treatment due to the poor understanding of its pathology.

Recent Findings

Coasting is a major feature of alcoholic neuropathy, largely due to chronic alcohol abuse. Its major features are hyperalgesia, allodynia, and burning pain. Even though much research was done in this area, still we do not have a full understanding of the mechanism of alcoholic neuropathy. However, some theories have been proposed. These include direct or indirect effects of alcohol metabolites, impaired axonal transport, suppressed excitatory nerve pathway activity, or imbalance in neurotransmitters. Activation of spinal cord microglia, mGlu5 spinal cord receptors, and hypothalamic-pituitary-adrenal axis also seem to be implicated in the pathophysiology of this alcoholic neuropathy. The goal of treatment is to impede further damage to the peripheral nerves while also restoring their normal physiology. Alcohol abstinence, intake of balanced diets, and treatment with medications are suggested including benfotiamine, alpha-lipoic acid, acetyl-l-carnitine, vitamin E, methylcobalamin, myo-inositol, N-acetylcysteine, capsaicin, tricyclic antidepressants, or antiepileptic drugs.

Summary

This review focuses on the many pathways that play a role in the onset and development of alcohol-induced neuropathy, as well as present the possible treatment strategies of this disorder, providing insights into a further search of new treatment modalities.

Constitutive Genetic Deletion of Hcn1 Increases Alcohol Preference during Adolescence

The hyperpolarization-activated cyclic nucleotide-gated channel (HCN), which underlies the hyperpolarization-activated cation current (I_h), has diverse roles in regulating neuronal excitability across cell types and brain regions. Recently, HCN channels have been implicated in preclinical models of substance abuse including alcohol. In the prefrontal cortex of rodents, HCN expression and I_h magnitude are developmentally regulated during adolescence and may be vulnerable to alcohol’s effects. In mice, binge alcohol consumption during the adolescent period results in a sustained reduction in I_h that coincides with increased alcohol consumption in adulthood, yet the direct role HCN channels have on alcohol consumption are unknown. Here, we show that the genetic deletion of Hcn1 causes an increase in alcohol preference on intermittent 2-bottle choice task in homozygous null (HCN1^−/−) male mice compared to wild-type littermates without affecting saccharine or quinine preference. The targeted viral deletion of HCN1 in pyramidal neurons of the medial prefrontal cortex resulted in a gradual loss of Hcn1 expression and a reduction in I_h magnitude during adolescence, however, this did not significantly affect alcohol consumption or preference. We conclude that while HCN1 regulates alcohol preference, the genetic deletion of Hcn1 in the medial prefrontal cortex does not appear to be the locus for this effect.

Alcohol-Responsive Hyperkinetic Movement Disorders-a Mechanistic Hypothesis

Patients with essential tremor, vocal tremor, torticollis, myoclonus-dystonia and posthypoxic myoclonus often benefit in a surprisingly rapid and robust manner from ingestion of a modest amount of alcohol (ethanol). Despite considerable investigation, the mechanism of ethanol’s ability to produce this effect remains a mystery. In this paper, we review the pharmacology of ethanol and its analogue GHB (or sodium oxybate), summarize the published literature of alcohol-responsive hyperkinetic movement disorders, and demonstrate videos of patients we have treated over the last fifteen years with either an ethanol challenge or with chronic sodium oxybate therapy. We then propose a novel explanation for this phenomenon—namely, that ingestion of modest doses of ethanol (or sodium oxybate) normalizes the aberrant motor networks underling these disorders. We propose that alcohol and its analogues improve clinical symptoms and their physiologic correlate by restoring the normal firing pattern of the major outflow pathways of the cerebellum (the Purkinje cells and deep cerebellar nuclei), We present evidence to support this hypothesis in animal models and in affected patients, and suggest future investigations to test this model.

Dopamine and Addiction

Addiction is commonly identified with habitual nonmedical self-administration of drugs. It is usually defined by characteristics of intoxication or by characteristics of withdrawal symptoms. Such addictions can also be defined in terms of the brain mechanisms they activate; most addictive drugs cause elevations in extracellular levels of the neurotransmitter dopamine. Animals unable to synthesize or use dopamine lack the conditioned reflexes discussed by Pavlov or the appetitive behavior discussed by Craig; they have only unconditioned consummatory reflexes. Burst discharges (phasic firing) of dopamine-containing neurons are necessary to establish long-term memories associating predictive stimuli with rewards and punishers. Independent discharges of dopamine neurons (tonic or pacemaker firing) determine the motivation to respond to such cues. As a result of habitual intake of addictive drugs, dopamine receptors expressed in the brain are decreased, thereby reducing interest in activities not already stamped in by habitual rewards.

Daily alcohol intake triggers aberrant synaptic pruning leading to synapse loss and anxiety-like behavior

Alcohol abuse adversely affects the lives of millions of people worldwide. Deficits in synaptic transmission and in microglial function are commonly found in human alcohol abusers and in animal models of alcohol intoxication. Here, we found that a protocol simulating chronic binge drinking in male mice resulted in aberrant synaptic pruning and substantial loss of excitatory synapses in the prefrontal cortex, which resulted in increased anxiety-like behavior. Mechanistically, alcohol intake increased the engulfment capacity of microglia in a manner dependent on the kinase Src, the subsequent activation of the transcription factor NF-κB, and the consequent production of the proinflammatory cytokine TNF. Pharmacological blockade of Src activation or of TNF production in microglia, genetic ablation of Tnf, or conditional ablation of microglia attenuated aberrant synaptic pruning, thereby preventing the neuronal and behavioral effects of the alcohol. Our data suggest that aberrant pruning of excitatory synapses by microglia may disrupt synaptic transmission in response to alcohol abuse.

Differential effects of ethanol on behavior and GABAA receptor expression in adult zebrafish (Danio rerio) with alternative stress coping styles

Variation in stress responses between individuals are linked to factors ranging from stress coping styles to sensitivity of neurotransmitter systems. Many anxiolytic compounds (e.g. ethanol) can increase stressor engagement through modulation of neurotransmitter systems and are used to investigate stress response mechanisms. There are two alternative suites of correlated behavioral and physiological responses to stressors (stress coping styles) that differ in exploration tendencies: proactive and reactive stress coping styles. By chronically treating individuals differing in stress coping style with ethanol, a GABA-acting drug, we assessed the role of the GABAergic system on the behavioral stress response. Specifically, we investigated resulting changes in stress-related behavior (i.e. exploratory behavior) and whole-brain GABAA receptor subunits (gabra1, gabra2, gabrd, & gabrg2) in response to a novelty stressor. We found that ethanol-treated proactive individuals showed lower stress-related behaviors than their reactive counterparts. Proactive individuals showed significantly higher expression of gabra1, gabra2, and gabrg2 compared to reactive individuals and ethanol treatment resulted in upregulation of gabra1 and gabrg2 in both stress coping styles. These results suggest that impacts of ethanol on stress-related behaviors vary by stress coping style and that expression of select GABAA receptor subunits may be one of the underlying mechanisms.

Preclinical methodological approaches investigating of the effects of alcohol on perinatal and adolescent neurodevelopment

Despite much evidence of its economic and social costs, alcohol use continues to increase. Much remains to be known as to the effects of alcohol on neurodevelopment across the lifespan and in both sexes. We provide a comprehensive overview of the methodological approaches to ethanol administration when using animal models (primarily rodent models) and their translational relevance, as well as some of the advantages and disadvantages of each approach. Special consideration is given to early developmental periods (prenatal through adolescence), as well as to the types of research questions that are best addressed by specific methodologies. The zebrafish is used increasingly in alcohol research, and how to use this model effectively as a preclinical model is reviewed as well.

24-Epibrassinolide protects against ethanol-induced behavioural teratogenesis in zebrafish embryo

Embryonic studies have demonstrated the neurotoxic, teratogenic, and neurobehavioral toxicity of ethanol (EtOH). Although multiple mechanisms may contribute to these effects, oxidative stress has been described as the major damage pathway. In this regard, natural antioxidants have the potential to counteract oxidative stress-induced cellular damage. Therefore, the present study aimed to investigate the potential protective role of 24-epibrassinolide (24-EPI), a natural brassinosteroid with proved antioxidant properties, in EtOH-induced teratogenic effects during early zebrafish development. Embryos (~2 h post-fertilization - hpf) were exposed to 1 % EtOH, co-exposed to 24-EPI (0.01, 0.1 and 1 μM) and to 24-EPI alone (1 μM) for 24 h. Following exposure, biochemical evaluations were made at 26 hpf, developmental analysis was made throughout the embryo-larval period, and behavioural responses were evaluated at 120 hpf. Exposure to 1 % EtOH caused an increase in the number of malformations, which were diminished by 24-EPI. In addition, EtOH induced an accumulation of GSSG and consequent reduction of GSH:GSSG ratio, indicating the involvement of oxidative mechanisms in the EtOH-induced effects. These were reverted by 24-EPI as proved by the GSSG levels and GSH:GSSG ratio that returned to control values. Furthermore, exposure to EtOH resulted in behavioural deficits at 120 hpf as observed by the disrupted response to an aversive stimulus, suggesting the involvement of neurotoxic mechanisms. 24-EPI restored the behavioural deficits observed in a dose-dependent manner. The absence of effects in the embryos exposed solely to 24-EPI showed its safety during the exposure period. In conclusion, EtOH caused developmental teratogenicity and behavioural toxicity by inducing glutathione changes, which were prevented by 24-EPI.

Ethanol-Induced Changes in Brain of Transgenic Mice Overexpressing DYRK1A

Alcoholism is a chronic relapsing disorder defined by loss of control over excessive consumption of ethanol despite damaging effects on the liver and brain. We previously showed that the overexpression in mice of Dyrk1A (TgDyrk1A, for dual-specificity tyrosine (Y) phosphorylation-regulated kinase 1A) reduces the severity of alcohol mediated liver injury. Ethanol consumption has also been associated with increased brain glutamate concentration that led to therapies targeting glutamatergic receptors and normalization of glutamatergic neurotransmission. Interestingly, mice overexpressing Dyrk1A (TgDyrk1A mice) present a reduction of glutamatergic brain transmission, which we propose could be protective against alcohol intake. To answer this question, we investigated the ethanol preference in TgDyrk1A mice using a two-bottle choice paradigm. TgDyrk1A mice showed a non-significant decrease of voluntary ethanol intake and ethanol preference compared with wild-type mice. At the peripheral level, mice overexpressing Dyrk1A show lower ethanol plasma levels, indicating a faster ethanol metabolism. At the end of the protocol, lasting 21 days, brains were extracted for protein analysis. Ethanol reduced levels of the synaptic protein PSD-95 and increased the glutamate decarboxylase GAD65, specifically in the cortex of TgDyrk1A mice. Our results suggest that overexpression of DYRK1A may cause different ethanol-induced changes in the brain.

Alcohol Consumption Reported during the COVID-19 Pandemic: The Initial Stage

Physical health is not the only area affected by the outbreak of the SARS-CoV-2 virus pandemic. There are also other consequences that have globally affected many millions at other levels, namely: Societal, political, economic, and cultural. This study aims to survey alcohol drinking throughout the pandemic so as to investigate those factors considered most relevant; i.e., sociodemographic and clinical. A longitudinal study was designed. The first (or initial) stage was completed between April 10–20 2020 on 443 subjects during the enforcement of the “Lockdown” in Poland. The second stage will be due in June 2020. As well as an in-house questionnaire, the study used: The Alcohol Use Disorder Identification Test (AUDIT), General Health Questionnaire (GHQ-28), Perceived Stress Scale (PSS-10), and the Brief COPE Inventory (Mini COPE). Alcohol was the most commonly used psychoactive substance (73%) identified. More than 30% changed their drinking habits because of the pandemic, with 16% actually drinking less, whilst 14% did so more. The former group was significantly younger than the latter. Amongst the stress-related coping strategies, it was found that current alcohol drinkers were significantly less able to find anything positive about the pandemic situation (positive reframing) and were mentally less able to cope. Those drinking more now were found to have been drinking more intensively before the pandemic started.

Parkin deficiency accentuates chronic alcohol intake-induced tissue injury and autophagy defects in brain, liver and skeletal muscle

Alcoholism leads to organ injury including mitochondrial defect and apoptosis with evidence favoring a role for autophagy dysregulation in alcoholic damage. Parkin represents an autosomal recessive inherited gene for Parkinson's disease and an important member of selective autophagy for mitochondria. The association between Parkinson's disease and alcoholic injury remains elusive. This study aimed to examine the effect of parkin deficiency on chronic alcohol intake-induced organ injury in brain, liver and skeletal muscle (rectus femoris muscle). Adult parkin-knockout (PRK-/-) and wild-type mice were placed on Liber-De Carli alcohol liquid diet (4%) for 12 weeks prior to assessment of liver enzymes, intraperitoneal glucose tolerance, protein carbonyl content, apoptosis, hematoxylin and eosin morphological staining, and mitochondrial respiration (cytochrome c oxidase, NADH:cytochrome c reductase and succinate:cytochrome c reductase). Autophagy protein markers were monitored by western blot analysis. Our data revealed that chronic alcohol intake imposed liver injury as evidenced by elevated aspartate aminotransferase and alanine transaminase, glucose intolerance, elevated protein carbonyl formation, apoptosis, focal inflammation, necrosis, microvesiculation, autophagy/mitophagy failure and dampened mitochondrial respiration (complex IV, complexes I and III, and complexes II and III) in the brain, liver and rectus femoris skeletal muscle. Although parkin ablation itself did not generate any notable effects on liver enzymes, insulin sensitivity, tissue carbonyl damage, apoptosis, tissue morphology, autophagy or mitochondrial respiration, it accentuated alcohol intake-induced tissue damage, apoptosis, morphological change, autophagy/mitophagy failure and mitochondrial injury without affecting insulin sensitivity. These data suggest that parkin plays an integral role in the preservation against alcohol-induced organ injury, apoptosis and mitochondrial damage.

Effect of ethanol on Munc13-1 C1 in Membrane: A Molecular Dynamics Simulation Study

BACKGROUND

EtOH has a significant effect on synaptic plasticity. Munc13-1 is an essential presynaptic active zone protein involved in priming the synaptic vesicle and releasing neurotransmitter in the brain. It is a peripheral membrane protein and binds to the activator, diacylglycerol (DAG)/phorbol ester at its membrane-targeting C1 domain. Our previous studies identified Glu-582 of C1 domain as the alcohol-binding residue (Das, J. et al, J. Neurochem., 126, 715-726, 2013).

METHODS

Here, we describe a 250 ns molecular dynamics (MD) simulation study on the interaction of EtOH and the activator-bound Munc13-1 C1 in the presence of varying concentrations of phosphatidylserine (PS).

RESULTS

In this study, Munc13-1 C1 shows higher conformational stability in EtOH than in water. It forms fewer hydrogen bonds with phorbol 13-acetate in the presence of EtOH than in water. EtOH also affected the interaction between the protein and the membrane and between the activator and the membrane. Similar studies in a E582A mutant suggest that these effects of EtOH are mostly mediated through Glu-582.

CONCLUSIONS

EtOH forms hydrogen bonds with Glu-582. While occupancy of the EtOH molecules at the vicinity (4Å) of Glu-582 is 34.4%, the occupancy in the E582A mutant is 26.5% of the simulation time. In addition, the amount of PS in the membrane influences the conformational stability of the C1 domain and interactions in the ternary complex. This study is important in providing the structural basis of EtOH's effects on synaptic plasticity.

Understanding the neurobiological effects of drug abuse: Lessons from zebrafish models

Drug abuse and brain disorders related to drug comsumption are public health problems with harmful individual and social consequences. The identification of therapeutic targets and precise pharmacological treatments to these neuropsychiatric conditions associated with drug abuse are urgently needed. Understanding the link between neurobiological mechanisms and behavior is a key aspect of elucidating drug abuse-related targets. Due to various molecular, biochemical, pharmacological, and physiological features, the zebrafish (Danio rerio) has been considered a suitable vertebrate for modeling complex processes involved in drug abuse responses. In this review, we discuss how the zebrafish has been successfully used for modeling neurobehavioral phenotypes related to drug abuse and review the effects of opioids, cannabinoids, alcohol, nicotine, and psychedelic drugs on the central nervous system (CNS). Moreover, we summarize recent advances in zebrafish-based studies and outline potential advantages and limitations of the existing zebrafish models to explore the neurochemical bases of drug abuse and addiction. Finally, we discuss how the use of zebrafish models may present fruitful approaches to provide valuable clinically translatable data.

Inhibition of Lrrk2 reduces ethanol preference in a model of acute exposure in zebrafish

Due to its multifactorial and yet to be fully understood origin, ethanol addiction is a field that still requires studies for the elucidation of novel genes and pathways that potentially influence the establishment and maintenance of addiction-like phenotypes. In this context, the present study aimed to evaluate the role of the LRRK2 pathway in the modulation of ethanol preference behavior in Zebrafish (Danio rerio). Using the behavioral Conditioned Place Preference (CPP) paradigm, we accessed the preference of animals for ethanol. Next, we evaluated the transcriptional regulation of the gene lrrk2 and the receptors drd1, drd2, grin1a, gria2a, and gabbr1b in the zebrafish brain. Additionally, we used a selective inhibitor of Lrrk2 (GNE-0877) to assess the role of this gene in the preference behavior. Our results revealed four distinct ethanol preference phenotypes (Light, Heavy, Negative Reinforcement, and Inflexible), each showing different transcriptional regulation patterns of the drd1, drd2, grin1a, gria2a, and gabbr1b receptors. We showed that the lrrk2 gene was hyperregulated only in the brains of the animals with the Inflexible phenotype. Most importantly, we showed, for the first time in the context of preference for ethanol, that treatment with the GNE-0877 inhibitor modulates the transcription of the target receptor genes and reduces the preference for ethanol in the animals of the Inflexible group. This result corroborates the hypothesis that the LRRK2 pathway is involved in the inflexible preference for ethanol behavior. Lastly, we identified a possible pharmacological target for the treatment of abusive preference behavior for ethanol.

Alcohol binge-drinking damage on the vestibulo-oculomotor reflex

PURPOSE

Binge drinking is associated with several adverse effects in multiple organs. This study aimed at evaluating the effects of a binge-like-drinking on the vestibulo-oculomotor reflex (VOR) using the video Head Impulse Test (vHIT) and the functional Head Impulse Test (fHIT).

METHODS

Eleven healthy men (age range 32-35 years) with moderate drinking habits and no history of vestibular dysfunction were enrolled. A preliminary assessment of breath alcohol concentration (BrAC) to check for zero alcohol value and a pre-intake evaluation of VOR using the vHIT and the fHIT were carried on. Then, the subjects were asked to take drinks with different alcohol content (8-40% ethanol by volume) according to their choice, consuming at least 5 standard drinks. Volunteers stopped drinking after 3 h. After a further 30 min, post-intake BrAC measurements and VOR analysis were repeated.

RESULTS

After alcohol intake, vHIT recorded an overall significant reduction of VOR gain (0.82 ± 0.07 on both sides) although the outcomes were below the normal range only in the four subjects with the highest blood alcohol levels. The post-intake fHIT outcomes were substandard in 9 participants, with a significant deterioration in performance (% of exact answers = 84.54 ± 11.05% on the left, 83.18 ± 14.53 on the right).

CONCLUSIONS

Binge drinking severely affects VOR; fHIT seems more sensitive than vHIT in the assessment of VOR function for complex vestibular lesions, such as those determined by ethanol, suggesting that fHIT could support vHIT in vestibular dysfunction assessment.

In vitro effects of Pueraria extract on ethanol-exposed microglia and neurons

Predominant health impacts from alcoholism are chronic neurologic deficits and hepatic dysfunction. Pueraria extract (PE) is a solution obtained from the dried root of Pueraria lobate and can reverse alcohol-induced hepatic damage. The present study aimed to elucidate the effects of PE on ethanol-induced injury in microglia and neurons. To confirm the reliability of the experimental approach, an in vivo demonstration of PE activity was used to verify its impact on hepatic damage in mice exposed to ethanol (ETOH). Subsequently, an in vitro assay was used to verify the effects of PE on ETOH-exposed microglia and neurons.PE reversed fibrosis and hyperplasia, adipocyte infiltration, hepatomegaly, hepatic function, lipid metabolism, indicators of oxidative stress, and morphological changes in hepatic cells, induced by ETOH exposure. The reliability of the experimental approach was thus confirmed. PE also reversed the activation of microglia and inflammatory-related cytokines and proteins induced by ETOH exposure. PE showed protective effects on neurons via inhibition of mitochondrial fission. in vivo and in vitro evidence indicated that PE might be useful in the treatment of both hepatic injury and neurologic deficits commonly observed in chronic alcoholism.

The transition to compulsion in addiction

Compulsion is a cardinal symptom of drug addiction (severe substance use disorder). However, compulsion is observed in only a small proportion of individuals who repeatedly seek and use addictive substances. Here, we integrate accounts of the neuropharmacological mechanisms that underlie the transition to compulsion with overarching learning theories, to outline how compulsion develops in addiction. Importantly, we emphasize the conceptual distinctions between compulsive drug-seeking behaviour and compulsive drug-taking behaviour (that is, use). In the latter, an individual cannot stop using a drug despite major negative consequences, possibly reflecting an imbalance in frontostriatal circuits that encode reward and aversion. By contrast, an individual may compulsively seek drugs (that is, persist in seeking drugs despite the negative consequences of doing so) when the neural systems that underlie habitual behaviour dominate goal-directed behavioural systems, and when executive control over this maladaptive behaviour is diminished. This distinction between different aspects of addiction may help to identify its neural substrates and new treatment strategies.

Inhibitors of cellular stress overcome acute effects of ethanol on hippocampal plasticity and learning

Ethanol intoxication can produce marked changes in cognitive function including states in which the ability to learn and remember new information is completely disrupted. These defects likely reflect changes in the synaptic plasticity thought to underlie memory formation. We have studied mechanisms contributing to the adverse effects of ethanol on hippocampal long-term potentiation (LTP) and provided evidence that ethanol-mediated LTP inhibition involves a form of metaplasticity resulting from local metabolism of ethanol to acetaldehyde and untimely activation of N-methyl-d-aspartate receptors (NMDARs), both of which are neuronal stressors. In the present studies, we sought to understand the role of cellular stress in LTP defects, and demonstrate that ethanol's effects on LTP in the CA1 hippocampal region are overcome by agents that inhibit cellular stress responses, including ISRIB, a specific inhibitor of integrated stress responses, and GW3965, an agonist that acts at liver X receptors (LXRs) and dampens cellular stress. The agents that alter LTP inhibition also prevent the adverse effects of acute ethanol on one trial inhibitory avoidance learning. Unexpectedly, we found that the LXR agonist but not ISRIB overcomes effects of ethanol on synaptic responses mediated by N-methyl-d-aspartate receptors (NMDARs). These results have implications for understanding the adverse effects of ethanol and possibly for identifying novel paths to treatments that can prevent or overcome ethanol-induced cognitive dysfunction.

Role of corticotropin-releasing factor in alcohol and nicotine addiction

The two most prevalent substance use disorders involve alcohol and nicotine, which are often co-abused. Robust preclinical and translational evidence indicates that individuals initiate drug use for the acute rewarding effects of the substance. The development of negative emotional states is key for the transition from recreational use to substance use disorders as subjects seek the substance to obtain relief from the negative emotional states of acute withdrawal and protracted abstinence. The neuropeptide corticotropin-releasing factor (CRF) is a major regulator of the brain stress system and key in the development of negative affective states. The present review examines the role of CRF in preclinical models of alcohol and nicotine abuse and explores links between CRF and anxiety-like, dysphoria-like, and other negative affective states. Finally, the present review discusses preclinical models of nicotine and alcohol use with regard to the CRF system, advances in molecular and genetic manipulations of CRF, and the importance of examining both males and females in this field of research.

NADPH oxidase contributes to oxidative damage and mitochondrial impairment induced by acute ethanol treatment in rat hippocampal neurons

Acute ethanol treatment induces neurodegeneration in cultured neurons and can lead to brain damage in animal models. Neuronal cells exposed to ethanol showed an increase in reactive oxygen species (ROS), oxidative damage and mitochondrial impairment contributing to synaptic failure. However, the underlying mechanisms of these events are not well understood. Here, we studied the contribution of NADPH oxidase, as a relevant source of ROS production in the brain, to mitochondrial impairment and oxidative stress induced by ethanol. We used primary hippocampal neurons subjected to an acute treatment of ethanol at increasing concentrations (25, 50, and 75 mM, 24 h), and we evaluated ROS production, mitochondrial function, and synaptic vesicle activity. Our studies showed that after ethanol administration, hippocampal neurons presented an increase in ROS levels, mitochondrial dysfunction, calcium handling defects, and synaptic impairment. Interestingly, treatment with the NADPH inhibitor, apocynin, significantly prevented oxidative stress, mitochondrial dysfunction, and the impairment of synaptic vesicle activity induced by ethanol treatment. These results indicate that NADPH oxidase could be a key participant in the molecular mechanism by which alcohol affects the brain.

Diverse types of genomic evidence converge on alcohol use disorder risk genes

BACKGROUND

Alcohol use disorder (AUD) is one of the most common forms of substance use disorders with a strong contribution of genetic (50%-60%) and environmental factors. Genome-wide association studies (GWAS) have identified a number of AUD-associated variants, including those in alcohol metabolism genes. These genetic variants may modulate gene expression, making individuals more susceptible to AUD. A long-term alcohol consumption can also change the transcriptome patterns of subjects via epigenetic modulations.

METHODS

To explore the interactive effect of genetic and epigenetic factors on AUD, we conducted a secondary analysis by integrating GWAS, CNV, brain transcriptome and DNA methylation data to unravel novel AUD-associated genes/variants. We applied the mega-analysis of OR (MegaOR) method to prioritise AUD candidate genes (AUDgenes).

RESULTS

We identified a consensus set of 206 AUDgenes based on the multi-omics data. We demonstrated that these AUDgenes tend to interact with each other more frequent than chance expectation. Functional annotation analysis indicated that these AUDgenes were involved in substance dependence, synaptic transmission, glial cell proliferation and enriched in neuronal and liver cells. We obtained a multidimensional evidence that AUD is a polygenic disorder influenced by both genetic and epigenetic factors as well as the interaction of them.

CONCLUSION

We characterised multidimensional evidence of genetic, epigenetic and transcriptomic data in AUD. We found that 206 AUD associated genes were highly expressed in liver, brain cerebellum, frontal cortex, hippocampus and pituitary. Our studies provides important insights into the molecular mechanism of AUD and potential target genes for AUD treatment.

Developmental stage and genotype dependent behavioral effects of embryonic alcohol exposure in zebrafish larvae

Fetal Alcohol Spectrum Disorders (FASD) represent a worldwide problem. The severity and types of symptoms of FASD vary, which may be due to the genotype of the fetus and the developmental stage at which the fetus is exposed to alcohol. The most prevalent forms of FASD present less severe symptoms, including behavioral and cognitive abnormalities, and arise from exposure to low amounts of alcohol consumed infrequently. Treating or diagnosing FASD patients has been difficult because we do not understand the mechanisms underlying FASD. Animal models, including the zebrafish, have been suggested to answer this question. Here, we present a proof of concept analysis studying the behavioral effects of embryonic alcohol exposure in one-week old juvenile zebrafish. We exposed zebrafish embryos at one of five developmental stages (8, 16, 24, 32, or 40 hour post-fertilization) to 0% (control) or 1% (vol/vol) ethanol for 2 h, and tested the behavior of these fish at their age of 7-9 days post-fertilization. We employed two genetically distinct zebrafish populations, a quasi-inbred AB derivative strain, and a genetically variable WT population. We report significant developmental time and genotype dependent effects of alcohol on certain measures of motor function and/or anxiety-like responses. For example, we found embryonic alcohol exposed AB fish to swim faster, vary their speed more, stop moving more often and turn less compared to control fish, alcohol induced changes that were absent or less robust in WT fish. We conclude that our results open new avenues to the identification of genetic mechanisms that mediate or influence alcohol induced developmental alteration of brain function and behavior, which, on the long run, may allow us to identify diagnostic biomarkers and treatment options for human FASD.

Role of the treatment environment in the effects of aripiprazole on ethanol-induced behavioral sensitization and conditioned place preference in female mice

BACKGROUND

Evidence suggests that aripiprazole, a partial dopamine D2 and serotonin 5-HT1A receptor agonist and 5-HT2A receptor antagonist, show significant efficacy in reducing alcohol use. We have previously demonstrated that treatment with aripiprazole blocked the reinstatement of cocaine-induced behavioral sensitization in a context-dependent manner, suggesting that the treatment environment may modulate the therapeutic effects of aripiprazole. The present study aimed to evaluate the effects of treatment with aripiprazole on ethanol-induced behavioral sensitization and conditioned place preference in female mice, and the role of the treatment environment in those effects.

METHODS

Adult female mice were either sensitized with ethanol injections in the open-field apparatus, or conditioned with ethanol in the conditioned place preference (CPP) apparatus. Animals were then treated with vehicle or 0.1 mg/kg aripiprazole paired to the test environment (open-field or CPP apparatus) or not (home-cage treatments) for 4 alternate days, and the subsequent expression of behavioral sensitization or CPP to ethanol was evaluated during or following an ethanol re-exposure, respectively.

RESULTS

Repeated treatment with aripiprazole attenuated the expression of ethanol-induced behavioral sensitization regardless of the treatment environment. Treatment with aripiprazole was only effective at preventing the reinstatement of ethanol-induced CPP when paired with the ethanol-associated environment, but not when administered in the home-cage.

CONCLUSIONS

The present findings corroborate previous studies suggesting the effectiveness of aripiprazole for the treatment of alcohol use disorder. Our results also point to an important role of the treatment environment in the therapeutic effects of aripiprazole in rodent models of ethanol abuse.