Voluntary Alcohol Consumption Research Articles

Combined Effects of Repetitive Mild Traumatic Brain Injury and Alcohol Drinking on the Neuroinflammatory Cytokine Response and Cognitive Behavioral Outcomes.

The relationship between alcohol consumption and traumatic brain injury (TBI) often focuses on alcohol consumption increasing the likelihood of incurring a TBI, rather than alcohol use outcomes after TBI. However, patients without a history of an alcohol use disorder can also show increased problem drinking after single or multiple TBIs. Alcohol and mild TBI share diffuse deleterious neurological impacts and cognitive impairments; therefore, the purpose of these studies was to determine if an interaction on brain and behavior outcomes occurs when alcohol is consumed longitudinally after TBI. To examine the impact of mild repetitive TBI (rmTBI) on voluntary alcohol consumption, mice were subjected to four mild TBI or sham procedures over a 2 week period, then offered alcohol (20% v/v) for 2 weeks using the two-bottle choice, drinking in the dark protocol. Following the drinking period, mice were evaluated for neuroinflammatory cytokine response or tested for cognitive and behavioral deficits. Results indicate no difference in alcohol consumption or preference following rmTBI as compared to sham; however, increases in the neuroinflammatory cytokine response due to alcohol consumption and some mild cognitive behavioral deficits after rmTBI and alcohol consumption were observed. These data suggest that the cytokine response to alcohol drinking and rmTBI + alcohol drinking is not necessarily aggregate, but the combination does result in an exacerbation of cognitive behavioral outcomes.

An Adolescent Porcine Model of Voluntary Alcohol Consumption Exhibits Binge Drinking and Motor Deficits in a Two Bottle Choice Test.

Alcohol is the most commonly abused substance leading to significant economic and medical burdens. Pigs are an attractive model for studying alcohol abuse disorder due to the comparable alcohol metabolism and consumption behavior, which are in stark contrast to rodent models. This study investigates the usage of a porcine model for voluntary binge drinking (BD) and a detailed analysis of gait changes due to motor function deficits during alcohol intoxication. Adolescent pigs were trained to drink increasing concentration (0-8%) of alcohol mixed in a 0.2% saccharin solution for 1h in a two bottle choice test for 2weeks. The training period was followed by a 3-week alcohol testing period, where animals were given free access to 8% alcohol in 0.2% saccharin solution and 0.2% saccharin water solution. Blood alcohol levels were tested and gait analysis was performed pre-alcohol consumption, last day of training, and Day 5 of each testing period. Pigs voluntarily consumed alcohol to intoxication at all timepoints with blood alcohol concentration (BAL) ≥80mg/dl. Spatiotemporal gait parameters including velocity, cadence, cycle time, swing time, stance time, step time, and stride length were perturbed as a result of intoxication. The stratification of the gait data based on BAL revealed that the gait parameters were affected in a dose-dependent manner. This novel adolescent BD porcine model with inherent anatomical and physiological similarities to humans display similar consumption and intoxication behavior that is likely to yield results that are translatable to human patients.

Pre-training naltrexone increases conditioned fear learning independent of adolescent alcohol consumption history

Our previous research has shown a relationship between low voluntary alcohol consumption and high conditioned fear in male Long Evans rats. Here, we examined whether differences in the endogenous opioid systems might be responsible for these differences. Rats received 6 weeks of chronic intermittent to 20% alcohol (v/v) or water-only from PND 26–66. Based on their consumption during the last 2 weeks of alcohol access, the alcohol-access rats were divided into high drinking (>2.5 g/kg/24-h) or low drinking (<2 g/kg/24-h). Rats were then given injections of the preferential mu opioid receptor antagonist naltrexone (1 mg/kg, s.c.) or the selective kappa opioid receptor antagonist LY2456302 (10 mg/kg, s.c.) prior to fear conditioning and were then tested for conditioned fear 2 days later. Pre-training naltrexone increased conditioned suppression of lever-pressing during training and testing, with no differences between high versus low alcohol drinkers or between water-only versus alcohol access groups (averaged across drinking levels). There was no effect of LY2456302 on conditioned fear in any comparison. We also found no differences between high and low alcohol drinkers and no reliable effect of prior alcohol access (averaged across drinking levels) on conditioned fear. Our experiment replicates and extends previous demonstrations that a preferential MOR antagonist can increase fear learning using conditioned suppression of lever-pressing as a fear measure. However, additional research is needed to determine the cause of the differences in conditioned fear that we previously observed (as they were not observed in the current experiments).

Attentional set shifting in HAP3, LAP3, and cHAP mice is unaffected by either genetic differences in alcohol preference or an alcohol drinking history.

Alcohol consumption may precede, or result from, behavioral inflexibility and contribute to individuals' difficulties ceasing drinking. Attentional set shifting tasks are an animal analog to a human behavioral flexibility task requiring recognition of a previous strategy as inappropriate, and the formation and maintenance of a novel strategy (Floresco, Block, & Tse, 2008). Abstinent individuals with alcohol use disorder, nonalcoholic individuals with a family history of alcoholism, and mice exposed to chronic-intermittent alcohol vapor show impaired behavioral flexibility (Gierski et al., 2013; Hu, Morris, Carrasco, & Kroener, 2015; Oscar-Berman et al., 2009). Behavioral flexibility deficits can be linked to frontal cortical regions connected to the striatum (Ragozzino, 2007), and alterations to the endocannabinoid system, implicated in drug seeking and consumption (Economidou et al., 2006; Serrano & Parsons, 2011), may affect these behaviors. Alcohol-preferring and nonpreferring rodents exhibit differences in CB1 receptor expression (CB1R; Hansson et al., 2007; Hungund & Basavarajappa, 2000), but whether dorsal striatal CB1Rs are important for other alcohol-related behaviors such as attentional set shifting tasks remains unclear. This study assesses whether selectively bred high (HAP) versus low alcohol-preferring mice differ in an operant attentional set shifting task or CB1R levels in the dorsal striatum and whether a history of voluntary alcohol consumption in crossed HAP mice exacerbates inflexibility. Contrary to our hypothesis, neither genetic differences in alcohol preference nor drinking affected set shifting. However, high alcohol-preferring mice-3 mice showed reduced levels of dorsal striatal CB1R compared with low alcohol-preferring-3 mice, suggesting that genetic differences in alcohol consumption may be mediated in part by striatal CB1R. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Role of toll-like receptor 7 (TLR7) in voluntary alcohol consumption

Overactivation of neuroimmune signaling has been linked to excessive ethanol consumption. Toll-like receptors (TLRs) are a major component of innate immune signaling and initiate anti- and pro-inflammatory responses via intracellular signal transduction cascades. TLR7 is upregulated in post-mortem brain tissue from humans with alcohol use disorder (AUD) and animals with prior exposure to ethanol. Despite this evidence, the role of TLR7 in the regulation of voluntary ethanol consumption has not been studied. We test the hypothesis that TLR7 activation regulates voluntary ethanol drinking behavior by administering a TLR7 agonist (R848) during an intermittent access drinking procedure in mice. Acute activation of TLR7 reduced ethanol intake, preference, and total fluid intake due, at least in part, to an acute sickness response. However, chronic pre-treatment with R848 resulted in tolerance to the adverse effects of the drug and a subsequent increase in ethanol consumption. To determine the molecular machinery that mediates these behavioral changes, we evaluated gene expression after acute and chronic TLR7 activation. We found that acute TLR7 activation produces brain region specific changes in expression of immune pathway genes, whereas chronic TLR7 activation causes downregulation of TLRs and blunted cytokine induction, suggesting molecular tolerance. Our results demonstrate a novel role for TLR7 signaling in regulating voluntary ethanol consumption. Taken together, our findings suggest TLR7 may be a viable target for development of therapies to treat AUD.

Taurine enhances voluntary alcohol intake and promotes anxiolytic-like behaviors in rats.

Taurine is an amino acid usually added to energy drinks. In rodents, acute taurine administration decreases voluntary alcohol intake, and subchronic administration restores different behavioral features impaired by alcohol withdrawal. In the present study, we evaluated the effects of chronic taurine treatment on voluntary alcohol consumption and changes in behavioral parameters in rats. Adult male Wistar rats were divided into two groups and were allowed to choose from two bottles containing 20% alcohol or 0.08% saccharin (vehicle solution), or two bottles containing vehicle, 24h per day, for 5 weeks. After 3 weeks, rats received 100mg/kg taurine (TAU) or saline (SAL) intraperitoneally once a day for 2 weeks, and daily alcohol consumption was monitored. On days 22 and 33, rats were tested in the open-field, and on day 34, they were exposed to the light/dark task (LDT). Our results show for the first time that chronic taurine treatment enhanced voluntary alcohol intake and preference in rats, and that these changes were accompanied by an anxiolytic-like phenotype in alcohol-treated rats, possibly due to its synergistic effect with alcohol on the dopaminergic and GABAergic systems.

Further evidence for the involvement of the PPARγ system on alcohol intake and sensitivity in rodents.

Peroxisome Proliferator Activator receptors (PPARs) are intracellular receptors that function as transcription factors, which regulate specific metabolic and inflammatory processes. PPARs are broadly distributed in the body and are also expressed in the central nervous system, especially in areas involved in addiction-related behavioral responses. Recent studies support a role of PPARs in alcoholism and pioglitazone: a PPARγ agonist used for treatment of type 2 diabetes showed efficacy in reducing alcohol drinking, stress-induced relapse, and alcohol withdrawal syndrome in rats. In the current work, we tested the pharmacological effects of pioglitazone on binge-like alcohol consumption using an intermittent two-bottle choice paradigm in Wistar rats and on the "drinking in the dark" (DID) model in mice with selective deletion of PPARγ in neurons. Our data show that repeated administration of pioglitazone (10, 30mg/kg) reduces high voluntary alcohol consumption in Wistar rats. Pre-treatment with the selective PPARγ antagonist GW9662 (5mg/kg) completely prevented the effect of pioglitazone, demonstrating that its action is specifically mediated by activation of PPARγ. In line with this result, repeated administration of pioglitazone (30mg/kg) attenuated binge alcohol consumption in PPARγ(+/+) mice. Whereas in PPARγ(-/-) mice, which exhibit reduced alcohol consumption, pioglitazone had no effect. Of note, PPARγ(-/-) mice exhibited lower patterns of alcohol drinking without showing difference in sucrose (control) intake. Interestingly, PPARγ(-/-) mice displayed a higher sensitivity to the sedative and ataxic effect of alcohol compared with their wild-type counterpart. Collectively, these data suggest that PPARγ agonists, and specifically pioglitazone, could be potential therapeutics for the treatment of binge alcohol drinking.

Voluntary alcohol consumption is increased in female, but not male, oxytocin receptor knockout mice.

IntroductionThe oxytocin (Oxt) system, while typically associated with the neural regulation of social behaviors, also plays a role in an individual's vulnerability to develop alcohol use disorders (AUD). In humans, changes to the Oxt system, due to early life experience and/or genetic mutations, are associated with increased vulnerability to AUD. While a considerable amount is known about Oxt's role in AUD in males, less is known or understood, about how Oxt may affect AUD in females, likely due to many clinical and preclinical studies of AUD not directly considering sex as a biological variable. This is unfortunate given that females are more vulnerable to the effects of alcohol and have increased alcohol consumption, as compared to males. Therefore, in the current study we wanted to determine whether genetic disruption of the Oxt receptor (Oxtr), that is, Oxtr knockout (−/−) mice, affected stress‐induced alcohol consumption in males and females. We hypothesized that genetic disruption of the Oxtr would result in increased stress‐induced alcohol consumption in both males and females compared to wild‐type (+/+) controls. Though, we predicted that these disruptions might be greater in female Oxtr −/− mice.MethodsTo test this hypothesis, a two‐bottle preference test was utilized along with the forced swim test (FST), and pre‐ and poststress alcohol consumption and preference measured within each sex (males and females were run separately). As a follow‐up experiment, a taste preference test, to control for possible genotypic differences in taste, was also performed.ResultsIn males, we found no significant genotypic differences in alcohol consumption or preference. However, in females, we found that genetic disruption of the Oxtr resulted in a greater consumption of alcohol both pre‐ and poststress compared to controls.ConclusionThese data suggest that in females, disruptions in Oxt signaling may contribute to increased vulnerability to alcohol‐associated addiction.

Sex-dependent effects of chronic intermittent voluntary alcohol consumption on attentional, not motivational, measures during probabilistic learning and reversal.

BackgroundForced alcohol (ethanol, EtOH) exposure has been shown to cause significant impairments on reversal learning, a widely-used assay of cognitive flexibility, specifically on fully-predictive, deterministic versions of this task. However, previous studies have not adequately considered voluntary EtOH consumption and sex effects on probabilistic reversal learning. The present study aimed to fill this gap in the literature.MethodsMale and female Long-Evans rats underwent either 10 weeks of voluntary intermittent 20% EtOH access or water only (H2O) access. Rats were then pretrained to initiate trials and learn stimulus-reward associations via touchscreen response, and subsequently required to select between two visual stimuli, rewarded with probability 0.70 or 0.30. In the final phase, reinforcement contingencies were reversed.ResultsWe found significant sex differences on several EtOH-drinking variables, with females reaching a higher maximum EtOH consumption, exhibiting more high-drinking days, and escalating their EtOH at a quicker rate compared to males. During early abstinence, EtOH drinkers (and particularly EtOH-drinking females) made more initiation omissions and were slower to initiate trials than H2O drinking controls, especially during pretraining. A similar pattern in trial initiations was also observed in discrimination, but not in reversal learning. EtOH drinking rats were unaffected in their reward collection and stimulus response times, indicating intact motivation and motor responding. Although there were sex differences in discrimination and reversal phases, performance improved over time. We also observed sex-independent drinking group differences in win-stay and lose-shift strategies specific to the reversal phase.ConclusionsFemales exhibit increased vulnerability to EtOH effects in early learning: there were sex-dependent EtOH effects on attentional measures during pretraining and discrimination phases. We also found sex-independent EtOH effects on exploration strategies during reversal. Future studies should aim to uncover the neural mechanisms for changes in attention and exploration in both acute and prolonged EtOH withdrawal.

Forced Abstinence From Alcohol Induces Sex-Specific Depression-Like Behavioral and Neural Adaptations in Somatostatin Neurons in Cortical and Amygdalar Regions.

Forced abstinence (FA) from alcohol has been shown to produce a variety of anxiety- and depression-like symptoms in animal models. Somatostatin (SST) neurons, a subtype of GABAergic neurons found throughout the brain, are a novel neural target with potential treatment implications in affective disorders, yet their role in alcohol use disorders (AUD) remains to be explored. Here, we examined the neuroadaptations of SST neurons during forced abstinence from voluntary alcohol consumption. Following 6 weeks of two-bottle choice alcohol consumption and protracted forced abstinence, male and female C57BL/6J mice exhibited a heightened, but sex-specific, depressive-like behavioral profile in the sucrose preference test (SPT) and forced swim test (FST), without changes in anxiety-like behaviors in the elevated plus maze (EPM) and open field test (OFT). FST-induced cFos expressions in the prefrontal cortex (PFC) and ventral bed nucleus of the stria terminalis (vBNST) were altered in FA-exposed female mice only, suggesting a sex-specific effect of forced abstinence on the neural response to acute stress. SST immunoreactivity in these regions was unaffected by forced abstinence, while differences were seen in SST/cFos co-expression in the vBNST. No differences in cFos or SST immunoreactivity were seen in the lateral central nucleus of the amygdala (CEA) and the basolateral amygdala (BLA). Additionally, SST neurons in female mice displayed opposing alterations in the PFC and vBNST, with heightened intrinsic excitability in the PFC and diminished intrinsic excitability in the vBNST. These findings provide an overall framework of forced abstinence-induced neuroadaptations in these key brain regions involved in emotional regulation and processing.

Brucine N-Oxide Reduces Ethanol Intake and Preference in Alcohol-Preferring Male Fawn-Hooded Rats.

Alcohol use disorder places a heavy burden on global public health systems and thus is in urgent need of improved pharmacotherapies. Previously, our group has demonstrated that 30mg/kg of the indole alkaloid brucine significantly attenuates alcohol-drinking behavior; however, the high toxicity, poor water solubility, short half-life, and limited therapeutic window of brucine restrain its clinical application as an antialcoholism medication. We subsequently hypothesized that the oxide of brucine (brucine N-oxide) would produce a similar behavioral effect without the risk profile associated with brucine. Male Fawn-Hooded rats with high innate alcohol preference underwent 2-bottle choice procedures (Experiments 1 to 3). Experiment 1 examined the effects of 7 daily BNO injections of 0, 30, 50, or 70mg/kg (s.c.) on voluntary alcohol consumption (n=9/group). Experiment 2 evaluated the impact of a single dose of 0 or 70mg/kg BNO on the increased alcohol intake induced by a 4-day alcohol deprivation (n=8/group). Experiment 3 tested the effect of 7 daily BNO injections of 0 or 70mg/kg (s.c.) on sucrose preference (n=6/group). Experiment 4 measured the median lethal dose (LD50) values of BNO and brucine to compare their acute toxicity in rats. Experiment 5 tested whether BNO (0, 30, 50, and 70mg/kg, s.c.) affected locomotor activity using an open-field paradigm (n=8/group). Finally, Experiment 6 evaluated the possible conditioned rewarding effects of 0, 30, 50, and 70mg/kg BNO using the conditioned place preference paradigm (n=6/group). BNO administration dose-dependently attenuated alcohol consumption without affecting food intake, total fluid consumption, or the natural preference for a sucrose solution, with 70mg/kg BNO reducing consumption by 22.8%. A single dose of 70mg/kg BNO significantly inhibited the alcohol deprivation effect. The LD50 values of BNO and brucine in rats were determined to be 1,103.5±177.0mg/kg and 264.6±17.7mg/kg, respectively. Finally, BNO administration did not affect spontaneous locomotor activity or induce a place preference. BNO may help to control excessive alcohol use and should be considered a treatment strategy for future study and development.

Drunk, dangerous and delusional: how legal concept-creep risks overcriminalization.

In the recent case of R v. Taj, the Court of Appeal of England and Wales upheld the conviction of a defendant who, in a psychotic delusional state, mistook his non-threatening victim to be a terrorist, violently attacking him. The law typically allows honest mistakes (even if unreasonable) as a basis for self-defence (in this case the defence of others). However, because Taj's delusions were found by the court to have been caused by voluntary alcohol consumption, special legal (prior-fault) intoxication rules were applied to block his defence; Taj was convicted and sentenced to 19years imprisonment for attempted murder. We focus here on the simple question-what does it mean to be intoxicated? On the facts, Taj did not have drugs active in his system at the time of the attack, but the court nonetheless insisted that Taj's delusional mistake was 'attributable to intoxication'; namely, to drink- and drug-taking in the previous days and weeks. This extended conception of intoxication was questionably distinguished from psychosis induced by withdrawal. Furthermore, the court was unreceptive to evidence of a long-standing, underlying mental health disorder. We argue that the court's expanded view of intoxication is problematic, in that intoxication-induced psychosis cannot be sharply distinguished from other causes such as mental disorders; and even if it could be distinguished, it should not give rise to blame and punishment in the same way as does conduct induced by chemically active intoxicants ('drug-on-board'). The courts' expansion of the definition of intoxication is both legally and forensically problematic, introducing legal vagaries where the clinical science is already vague; and with intoxication frequently interlocking with historic intoxication and secondary or comorbid mental health conditions, the decision risks inappropriately and/or over-criminalizing defendants.

Microglia depletion and alcohol: Transcriptome and behavioral profiles.

Alcohol abuse induces changes in microglia morphology and immune function, but whether microglia initiate or simply amplify the harmful effects of alcohol exposure is still a matter of debate. Here, we determine microglia function in acute and voluntary drinking behaviors using a colony-stimulating factor 1 receptor inhibitor (PLX5622). We show that microglia depletion does not alter the sedative or hypnotic effects of acute intoxication. Microglia depletion also does not change the escalation or maintenance of chronic voluntary alcohol consumption. Transcriptomic analysis revealed that although many immune genes have been implicated in alcohol abuse, downregulation of microglia genes does not necessitate changes in alcohol intake. Instead, microglia depletion and chronic alcohol result in compensatory upregulation of alcohol-responsive, reactive astrocyte genes, indicating astrocytes may play a role in regulation of these alcohol behaviors. Taken together, our behavioral and transcriptional data indicate that microglia are not the primary effector cell responsible for regulation of acute and voluntary alcohol behaviors. Because microglia depletion did not regulate acute or voluntary alcohol behaviors, we hypothesized that these doses were insufficient to activate microglia and recruit them to an effector phenotype. Therefore, we used a model of repeated immune activation using polyinosinic:polycytidylic acid (poly(I:C)) to activate microglia. Microglia depletion blocked poly(I:C)-induced escalations in alcohol intake, indicating microglia regulate drinking behaviors with sufficient immune activation. By testing the functional role of microglia in alcohol behaviors, we provide insight into when microglia are causal and when they are consequential for the transition from alcohol use to dependence.

Assessing effects of oxytocin on alcohol consumption in socially housed prairie voles using radio frequency tracking.

Alcohol use disorder affects millions of people each year. Currently approved pharmacotherapies have limited success in treating this disorder. Evidence suggests that this lack of success is partly due to how these pharmacotherapies are tested in preclinical settings. The vast majority of preclinical studies assessing the effects of pharmacotherapies on alcohol or drug self-administration are done in individually housed animals. However, it is known that alcohol and drug intake are heavily influenced by social settings. Here, we adapted radio frequency tracking technology to determine the effects of oxytocin, a potential therapy for alcohol use disorder, on alcohol consumption in socially housed male and female prairie voles. Voluntary alcohol consumption in these animals resulted in high daily alcohol intakes, blood ethanol concentrations that are considered intoxicating, and central changes in FosB immunoreactivity, indicative of changes in neural activity. Prairie voles that received oxytocin temporarily reduced alcohol consumption but not alcohol preference, compared with control prairie voles regardless whether their cagemates received a similar treatment or not. Our results demonstrate that oxytocin can decrease consummatory behaviors in the presence of peers that are not receiving this treatment, and therefore, its potential use in clinical trials is warranted. Moreover, effectiveness of other pharmacotherapies in preclinical studies can be tested in mixed-treatment socially housed animals similarly to clinical studies in humans.

Toxicological Assessment of the Role of Alcohol and Drugs in Drug-Facilitated Sexual Assault Cases in New Zealand.

This report details the toxicology profile of victims of drug-facilitated sexual assault (DFSA) in New Zealand from 2015 to 2018. This study represents all of the toxicology results for DFSA cases in New Zealand during this time period, of which there were 161 cases. Blood and urine samples were screened for legal and illicit drugs in addition to testing for alcohol and correlating alcohol concentration with sampling delay. Our results indicate that increased delay in sampling time resulted in a corresponding decrease in alcohol concentration. In victims who had declared alcohol use but of which none was detected, the average sampling time was 14hours for blood and 17hours for urine, which is in excess of the average sampling delay for even the lowest alcohol-positive samples. The most frequently detected alcohol concentration was in the range of 51-80mg/100mL for blood and 121-200mg/100mL for urine with an average sampling time of 8.5 and 6.5hours, respectively. We also examined acetone concentrations in alcohol-positive samples, and our results indicate that 82% of blood alcohol-positive samples contained acetone at concentrations between 5 and 10mg/L and 68% of alcohol-positive urine samples contained acetone at a concentration >20mg/L. It may be that the nature of sexual assault affects an individual's metabolism of alcohol and results in increased acetone production. Cannabis was the most commonly detected illicit drug, followed by methamphetamine. In relation to medicinal drugs, there was a high usage of antidepressants and antipsychotics, suggesting the victims may have been people of vulnerable personality. Based on case information, it does not appear there are many cases where stupefaction by unknown administration of a drug has occurred, instead loss of consent through voluntary alcohol and drug consumption is more common and poses a greater risk than surreptitious drug administration.

Intermittent Ethanol Access Increases Sensitivity to Social Defeat Stress

Comorbidity between alcoholism and depression is extremely common. Recent evidence supports a relationship between alcohol exposure and stress sensitivity, an underlying factor in the development of depression. Our laboratory has recently shown that chronic alcohol gavage increases sensitivity to social defeat stress (SDS). However, the effects of voluntary alcohol consumption, resulting from protocols such as intermittent ethanol access (IEA), on defeat stress sensitivity have yet to be elucidated. We first assessed the effects of 4weeks of IEA to 20% alcohol on sensitivity to subthreshold SDS exposure. Next, to examine neuroinflammatory mechanisms, we analyzed gene expression of inhibitor of NFkB (IkB) following IEA or chronic alcohol exposure (10days of 3.0g/kg alcohol via intragastric gavage). Then, we quantified NFkB activation via β-galactosidase immunohistochemistry following IEA or chronic alcohol gavage in NFkB-LacZ mice. IEA-exposed mice displayed an increase in sensitivity to subthreshold SDS compared to water-drinking controls. We also found that IkB gene expression was decreased in the nucleus accumbens (NAC) and amygdala (AMY) following IEA but was not altered following chronic alcohol gavage. Finally, we observed increased NFkB activity in the central amygdala (CEA), basolateral amygdala (BLA), and medial amygdala (MEA) after IEA, and increased NFkB activity solely in the CEA following chronic alcohol gavage. These findings further corroborate that prior alcohol exposure, in this case intermittent voluntary consumption, can impact development of depressive-like behavior by altering stress sensitivity. Furthermore, our results suggest the CEA as a potential mediator of alcohol's effects on stress sensitivity, as NFkB was activated in this region following both IEA and chronic alcohol gavage. Thus, this study provides novel insight on alterations in the NFkB pathway and identifies specific regions to target in future experiments assessing the functional role of NFkB in these processes.

Activation of Melanocortin-4 Receptor Inhibits Both Neuroinflammation Induced by Early Exposure to Ethanol and Subsequent Voluntary Alcohol Intake in Adulthood in Animal Models: Is BDNF the Key Mediator?

The concept that neuroinflammation induced by excessive alcohol intake in adolescence triggers brain mechanisms that perpetuate consumption has strengthened in recent years. The melanocortin system, composed of the melanocortin 4 receptor (MC4R) and its ligand α-melanocyte-stimulating hormone (α-MSH), has been implicated both in modulation of alcohol consumption and in ethanol-induced neuroinflammation decrease. Chronic alcohol consumption in adolescent rats causes a decrease in an α-MSH release by the hypothalamus, while the administration of synthetic agonists of MC4R causes a decrease in neuroinflammation and a decrease in voluntary alcohol consumption. However, the mechanism that connects the activation of MC4R with the decrease of both neuroinflammation and voluntary alcohol consumption has not been elucidated. Brain-derived neurotrophic factor (BDNF) has been implicated in alcohol drinking motivation, dependence and withdrawal, and its levels are reduced in alcoholics. Deficiencies in BDNF levels increased ethanol self-administration in rats. Further, BDNF triggers important anti-inflammatory effects in the brain, and this could be one of the mechanisms by which BDNF reduces chronic alcohol intake. Interestingly, MC4R signaling induces BDNF expression through the activation of the cAMP-responsive element-binding protein (CREB). We hypothesize that ethanol exposure during adolescence decreases the expression of α-MSH and hence MC4R signaling in the hippocampus, leading to a lower BDNF activity that causes dramatic changes in the brain (e.g., neuroinflammation and decreased neurogenesis) that predispose to maintain alcohol abuse until adulthood. The activation of MC4R either by α-MSH or by synthetic agonist peptides can induce the expression of BDNF, which would trigger several processes that lead to lower alcohol consumption.

Inescapable exposure to the Barnes maze increases preference for alcohol over water in rats: Implications for depression and anxiety

Various sources of stress induce alcohol intake in rodents, including inescapable shocks, physical restraint, and reward loss. One hypothesis maintains that alcohol intake increases because its anxiolytic properties reduce negative emotion. A series of experiments explored this hypothesis using escapable vs. inescapable exposure to the well-lit circular platform of a Barnes maze in a master/yoked (M/Y) design, with pairs of rats matched in the amount of time on the lighted platform, but differing in terms of the presence vs. absence of an escape box. In Experiment 1 the M/Y design was validated as a means of producing rapid acquisition of escape behavior in master animals. In Experiment 2, immediate postsession access to a 2-h, 2-bottle preference test with 8 % alcohol and water resulted in a higher increase in preference for alcohol over water across sessions in yoked animals compared to master animals. Group differences were not observed when animals had access to water in both bottles. Higher preference for 8 % alcohol in yoked vs. master animals was also observed when the Barnes maze and preference test were separated by a 1-h interval (Experiment 3). However, voluntary alcohol consumption was similar in master and yoked animals when the order of exposure to the Barnes maze and fluid consumption was reversed (Experiment 4) or when the threat level was reduced by using a dim light over the Barnes maze (Experiment 5). Increased preference for alcohol after inescapable exposure to the Barnes maze is consistent with the hypothesis that alcohol alleviates negative mood and anxiety induced by an inescapable threat. This animal model is relevant to an understanding of the initial stages of co-morbidity between depression, anxiety, and alcohol use.

Targeting liver aldehyde dehydrogenase-2 prevents heavy but not moderate alcohol drinking

Aldehyde dehydrogenase 2 (ALDH2), a key enzyme for detoxification the ethanol metabolite acetaldehyde, is recognized as a promising therapeutic target to treat alcohol use disorders (AUDs). Disulfiram, a potent ALDH2 inhibitor, is an approved drug for the treatment of AUD but has clinical limitations due to its side effects. This study aims to elucidate the relative contribution of different organs in acetaldehyde clearance through ALDH2 by using global- (Aldh2-/-) and tissue-specific Aldh2-deficient mice, and to examine whether liver-specific ALDH2 inhibition can prevent alcohol-seeking behavior. Aldh2-/- mice showed markedly higher acetaldehyde concentrations than wild-type (WT) mice after acute ethanol gavage. Acetaldehyde levels in hepatocyte-specific Aldh2 knockout (Aldh2Hep-/-) mice were significantly higher than those in WT mice post gavage, but did not reach the levels observed in Aldh2-/- mice. Energy expenditure and motility were dramatically dampened in Aldh2-/- mice, but moderately decreased in Aldh2Hep-/- mice compared to controls. In the 2-bottle paradigm and the drinking-in-the-dark model, Aldh2-/- mice drank negligible volumes from ethanol-containing bottles, whereas Aldh2Hep-/- mice showed reduced alcohol preference at high but not low alcohol concentrations. Glial cell- or neuron-specific Aldh2 deficiency did not affect voluntary alcohol consumption. Finally, specific liver Aldh2 knockdown via injection of shAldh2 markedly decreased alcohol preference. In conclusion, although the liver is the major organ responsible for acetaldehyde metabolism, a cumulative effect of ALDH2 from other organs likely also contributes to systemic acetaldehyde clearance. Liver-targeted ALDH2 inhibition can decrease heavy drinking without affecting moderate drinking, providing molecular basis for hepatic ALDH2 targeting/editing for the treatment of AUD.

Chronic voluntary alcohol consumption causes persistent cognitive deficits and cortical cell loss in a rodent model

Chronic alcohol use is associated with cognitive decline that impedes behavioral change during rehabilitation. Despite this, addiction therapy does not address cognitive deficits, and there is poor understanding regarding the mechanisms that underlie this decline. We established a rodent model of chronic voluntary alcohol use to measure ensuing cognitive effects and underlying pathology. Rats had intermittent access to alcohol or an isocaloric solution in their home cage under voluntary 2-bottle choice conditions. In Experiments 1 and 2 cognition was assessed using operant touchscreen chambers. We examined performance in a visual discrimination and reversal task (Experiment 1), and a 5-choice serial reaction time task (Experiment 2). For Experiment 3, rats were perfused immediately after cessation of alcohol access period, and volume, cell density and microglial populations were assessed in the prefrontal cortex and striatum. Volume was assessed using the Cavalieri probe, while cell and microglial counts were estimated using unbiased stereology with an optical fractionator. Alcohol-exposed and control rats showed comparable acquisition of pairwise discrimination; however, performance was impaired when contingencies were reversed indicating reduced behavioral flexibility. When tested in a 5-choice serial reaction time task alcohol-exposed rats showed increased compulsivity and increased attentional bias towards a reward associated cue. Consistent with these changes, we observed decreased cell density in the prefrontal cortex. These findings confirm a detrimental effect of chronic alcohol and establish a model of alcohol-induced cognitive decline following long-term voluntary intake that may be used for future intervention studies.