Reduced Alcohol Self-administration Research Articles

Mechanical acupuncture at HT7 attenuates alcohol self-administration in rats by modulating neuroinflammation and altering mPFC-habenula-VTA circuit activity.

Alcohol use disorder is a chronic disorder with significant limitations in pharmacological treatments, necessitating the exploration of non-pharmacological interventions. We used a model of alcohol self-administration (10% v/v) to analyze behavioral, neurochemical, and signaling mechanisms. Our findings demonstrate that stimulation of the HT7 acupuncture point significantly decreased the frequency of active lever presses in rats self-administering alcohol (p < 0.05). Alcohol self-administration increased microglial activity and sigma 1 receptor expression in the habenula (Hb), while HT7 stimulation mitigated these effects, decreasing microglial activity and sigma 1 receptor levels (p < 0.05). Additionally, alcohol self-administration reduced brain-derived neurotrophic factor (BDNF) expression in the medial prefrontal cortex (mPFC) and increased tyrosine hydroxylase (TH) levels in the ventral tegmental area (VTA) (p < 0.05). HT7 stimulation reversed these alterations by increasing BDNF expression in the mPFC and decreasing TH levels in the VTA (p < 0.05). Further investigation revealed that BDNF microinjection into the mPFC inhibited sigma 1 receptor activity in the Hb, while microglial inhibition in the Hb decreased TH expression in the VTA (p < 0.05). The administration of the microglial inhibitor MINO to the Hb also reduced alcohol self-administration (p < 0.05). These results suggest that HT7 stimulation regulates the mPFC-Hb-VTA circuit, leading to decreased alcohol-seeking behavior. Our study demonstrates that HT7 acupuncture can modulate the mPFC-Hb-VTA circuit, providing a potential non-pharmacological treatment for alcohol-seeking behavior by influencing microglial activity, sigma 1 receptor expression, and TH levels. These findings contribute to a deeper understanding of the neural mechanisms underlying acupuncture's therapeutic effects on alcohol use disorder.

Region-Specific Gene Expression Changes Associated with Oleoylethanolamide-Induced Attenuation of Alcohol Self-Administration.

Oleoylethanolamide (OEA) is a lipid with anti-inflammatory activity that modulates multiple reward-related behaviors. Previous studies have shown that OEA treatment reduces alcohol self-administration (SA) while inhibiting alcohol-induced inflammatory signaling. Nevertheless, the specific mechanisms that OEA targets to achieve these effects have not been widely explored. Here, we tested the effects of OEA treatment during alcohol SA, extinction or previous to cue-induced reinstatement of alcohol seeking. In addition, we measured gene expression changes in the striatum and hippocampus of relevant receptors for alcohol consumption (Drd1, Drd2, Cnr1, Oprm) as well as immune-related proteins (Il-6, Il-1β, Tlr4) and the brain-derived neurotrophic factor (Bdnf). Our results confirmed that when administered contingently, systemic OEA administration reduced alcohol SA and attenuated cue-induced reinstatement. Interestingly, we also observed that OEA treatment reduced the number of sessions needed for the extinction of alcohol seeking. Biochemical analyses showed that OEA induced gene expression changes in dopamine and cannabinoid receptors in the striatum and hippocampus. In addition, OEA treatment modulated the long-term immune response and increased Bdnf expression. These results suggest that boosting OEA levels may be an effective strategy for reducing alcohol SA and preventing relapse.

Psilocybin reduces alcohol self-administration via selective left nucleus accumbens activation in rats.

The use of psilocybin to treat alcohol use disorder is very promising, but its mechanisms of action remain poorly understood. We combined behavioural, pharmacological and gene expression analyses to decipher the mechanisms of action of psilocybin, for the first time, when injected into the brain. Male Long Evans rats underwent chronic operant ethanol self-administration before testing the effect of intraperitoneal psilocybin or directly within the nucleus accumbens core or the ventral tegmental area. Transcripts from the dopaminergic system were quantified in the nucleus accumbens and prefrontal cortex. Psilocybin significantly reduced (by 50%) ethanol self-administration when injected 4 h before the session either intraperitoneally (1 mg/kg) or directly within the left nucleus accumbens (0.15 μg) but not the right nucleus accumbens or the left ventral tegmental area. The effect of intraperitoneal injection of psilocybin was prevented by intra-left nucleus accumbens injection of 0.3 μg of the 5-HT2A receptor antagonist ketanserin. In rats that self-administered ethanol but not in those self-administering saccharin, dopamine D2 receptor (D2R) mRNA was increased in both the nucleus accumbens and the prefrontal cortex by psilocybin, while dopamine D1 receptor mRNA was increased only in the prefrontal cortex. As in humans, psilocybin reduced ethanol self-administration in rats through the 5-HT2A receptor within the left nucleus accumbens, possibly through increased D2R expression. Our results open unexpected perspectives regarding the hemispheric lateralization of psychedelic effects.

A randomized trial of the effects of COMT inhibition on subjective response to alcohol: Moderation by baseline COMT activity and mediation of alcohol self-administration.

Poor inhibitory control and enhanced subjective response to alcohol are interrelated risk factors for alcohol use disorder (AUD) that share underlying neural substrates, including dopamine signaling in the right prefrontal cortex, a potential target for pharmacological intervention. Cortical dopamine inactivation is primarily regulated by catechol-O-methyltransferase (COMT), an enzyme with large variation in activity as a function of the COMT rs4680 (val158met) single nucleotide polymorphism. In a previous randomized, placebo-controlled trial of the COMT inhibitor tolcapone (200 mg TID) in non-treatment-seeking participants with AUD, we found that tolcapone, relative to placebo, reduced alcohol self-administration only among rs4680 val-allele homozygotes, whose COMT activity is higher than in met-allele carriers. We conducted secondary analyses of the effects of tolcapone and baseline COMT activity, as indexed by both rs4680 genotype and an enzymatic activity assay, on the subjective response to alcohol in a bar-laboratory paradigm among 60 participants in the previous trial. Tolcapone did not affect alcohol-induced stimulation or sedation more than placebo. However, baseline COMT activity moderated the effects of the drug on both outcomes, such that tolcapone-treated participants with higher baseline COMT activity had less stimulation (p = 0.008) and sedation (p = 0.053) than participants with lower baseline COMT activity and those treated with placebo. Additionally, alcohol-induced stimulation significantly mediated the interacting effects of baseline COMT activity and tolcapone on bar-laboratory self-administration. Tolcapone may reduce subjective response to alcohol more effectively among individuals with preexisting high COMT activity an effect that could account for the drug's reduction of alcohol consumption among these individuals.

Novel RXFP3 negative allosteric modulator RLX-33 reduces alcohol self-administration in rats.

There is much interest in identifying novel pharmacotherapeutic targets that improve clinical outcomes for the treatment of alcohol use disorder (AUD). One promising target for therapeutic intervention is the relaxin family peptide 3 (RXFP3) receptor, a cognate receptor for neuropeptide relaxin-3, which has previously been implicated in regulating alcohol drinking behavior. Recently, we developed the first small-molecule RXFP3-selective negative allosteric modulator (NAM) RLX-33. Therefore, the goal of the present work was to characterize the impact of this novel NAM on affective-related behaviors and alcohol self-administration in rats. First, the effects of RLX-33 were tested on alcohol and sucrose self-administration in Wistar and alcohol-preferring P rats to determine the dose-response profile and specificity for alcohol. Then, we assessed the effects of systemic RLX-33 injection in Wistar rats in a battery of behavioral assays (open-field test, elevated zero maze, acoustic startle response test, and prepulse inhibition) and tested for alcohol clearance. We found that the lowest effective dose (5 mg/kg) reduced alcohol self-administration in both male and female Wistar rats, while in alcohol-preferring P rats, this effect was restricted to males, and there were no effects on sucrose self-administration or general locomotor activity. The characterization of affective and metabolic effects in Wistar rats generally found few locomotor, affective, or alcohol clearance changes, particularly at the 5 mg/kg dose. Overall, these findings are promising and suggest that RXFP3 NAM has potential as a pharmacological target for treating AUD.

Glucagon-like peptide-1 receptors in nucleus accumbens, ventral hippocampus, and lateral septum reduce alcohol reinforcement in mice.

Glucagon-like peptide 1 (GLP-1) receptor agonists can decrease alcohol intake by central mechanisms that are still poorly understood. The lateral septum (LS) and the ventral/caudal part of the hippocampus are enriched in GLP-1 receptors, and activity in these regions was shown to modulate reward-related behaviors. Using microinfusions of the GLP-1 receptor agonist exendin-4 in mice trained to self-administer oral alcohol in an operant assay, we tested whether pharmacological stimulation of GLP-1 receptors in hippocampus and LS decrease alcohol self-administration. We report that infusion of exendin-4 in the ventral hippocampus or LS was sufficient to reduce alcohol self-administration with as large effect sizes as we previously reported with systemic exendin-4 administration. Infusion of exendin-4 into the nucleus accumbens also reduced alcohol self-administration, as anticipated based on earlier reports, while infusion of exendin-4 into the caudate-putamen (dorsal striatum) had little effect, consistent with lack of GLP-1 receptor expression in this region. The distribution of exendin-4 after infusion into the LS or caudate putamen was visualized using a fluorescently labeled ligand. These findings add to our understanding of the circuit-level mechanisms underlying the ability of GLP-1 receptor agonists to reduce alcohol self-administration. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Pharmacological administration of 3α,5α-THP into the nucleus accumbens core increases 3α,5α-THP expression and reduces alcohol self-administration.

Alcohol affects multiple circuits in the brain, mainly disrupting the delicate balance between inhibitory γ-aminobutyric acid (GABA) transmission and excitatory glutamate signaling in brain areas involved in reward circuits. These include the amygdala, nucleus accumbens (Acb), and ventral tegmental area (VTA). This action impairs circuits that regulate behavioral control of craving and alcohol seeking and intake. Studies in both rodent models and postmortem human brain of patients with alcohol use disorder (AUD) have highlighted the association between the loss of GABAergic inhibition and the development of addiction. The neurosteroid (3α,5α)-3-hydroxypregnan-20-one (3α,5α-THP) is a potent positive modulator of GABAA receptors. Chronic alcohol consumption reduces 3α,5α-THP levels, resulting in decreased GABA inhibition. We previously demonstrated that enhancing neurosteroid biosynthesis by overexpression of the cholesterol side-chain cleavage enzyme P450scc decreased alcohol intake in male alcohol-preferring rats (P-rats). While most of the evidence of alcohol-induced alterations comes from studies in male subjects, some data show that females are more vulnerable to alcohol's effects than males. In this study, we investigated the ability of 3α,5α-THP direct infusions in two brain regions that contribute to alcohol reinforcement, the VTA and Acb core (AcbC), to regulate alcohol self-administration in female P-rats. Administration of 3α,5α-THP into the AcbC increased 3α,5α-THP-positive cell expression in this area and reduced alcohol self-administration. By contrast, 3α,5α-THP infusion into the VTA did not significantly affect alcohol self-administration, though trends for a reduction were found. Our results show that local increases in 3α,5α-THP in the AcbC may alter mesolimbic activity that drives a reduction in alcohol self-administration.

COPE and oxytocin for the treatment of co-occurring PTSD and alcohol use disorder: Design and methodology of a randomized controlled trial in U.S. military veterans

BackgroundA significant proportion of individuals with alcohol use disorder (AUD) also meet criteria for posttraumatic stress disorder (PTSD). Military veterans are at increased risk for developing co-occurring AUD/PTSD, with prevalence rates 2–4 times higher than the general population. Research is needed to develop more effective treatments for this common comorbidity. The current investigation addresses this need by examining the synergistic effects of a novel pharmacotherapy combined with psychotherapy for co-occurring AUD/PTSD among veterans. Accumulating evidence suggests that the neuropeptide oxytocin (OT) is a promising pharmacotherapy to augment psychotherapy for AUD/PTSD. OT targets neurobiological and behavioral dysregulation common to both AUD and PTSD, in particular, corticolimbic connectivity. Human and animal studies show OT reduces alcohol self-administration, tolerance, and withdrawal; enhances fear extinction; and promotes prosocial behaviors. The current study builds on previous work by examining OT among veterans with AUD/PTSD receiving Concurrent Treatment of PTSD and Substance Use Disorders using Prolonged Exposure (COPE), an evidence-based integrated treatment. MethodsThis paper describes the rationale, design, and methodology of a Stage II, 12-week, double-blind, randomized clinical trial of intranasal OT (40 IU) versus placebo combined with COPE among veterans (N = 180) with current AUD/PTSD. In addition, the effects of treatment on corticolimbic connectivity will be examined using functional magnetic resonance imaging (fMRI) at pre- and post-treatment. ConclusionsThe proposed study will provide new knowledge and mechanistic insights to accelerate research in this understudied area and may lead to improved treatment outcomes for co-occurring AUD/PTSD.ClinicalTrials.gov: NCT04523922.

Effects of pimavanserin and lorcaserin on alcohol self-administration and reinstatement in male and female rats

The neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) modulates fundamental motivational processes, and the neurochemical and behavioural effects of drugs of abuse. Recently, attention has focused on the role of 5-HT acting via 5-HT2A and 5-HT2C receptor sub-types in this regard. We examined the impact of manipulating 5-HT2A and 5-HT2C receptor mediated function on several aspects of alcohol self-administration and alcohol-seeking behaviour in male and female rats. Specifically, experiments investigated the effect of the 5-HT2A inverse agonist/antagonist pimavanserin, and the 5-HT2C receptor agonist lorcaserin on these behaviours. In male and female rats trained to respond for alcohol reinforcement on fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement pimavanserin (0.3, 1 and 3 mg/kg) had no consistent effect on responding. Lorcaserin (0.25, 0.5 and 1 mg/kg) reduced these behaviours in both sexes. Following extinction of responding for alcohol, alcohol-seeking was reinstated by cues previously paired with alcohol. Pimavanserin (1 mg/kg) and lorcaserin (0.5 mg/kg) significantly reduced this reinstatement. In a two-bottle 24 h intermittent access procedure pimavanserin had no significant effects, but lorcaserin reduced alcohol consumption in both sexes at 1, 4 and 24 h after access to alcohol was allowed. Finally, as determined using in vivo microdialysis, alcohol increased, and lorcaserin (0.5 mg/kg) reduced, extracellular levels of DA in the NAc in male rats. In rats treated with lorcaserin prior to alcohol injection the net effect was that DA levels were not changed compared to those measured in control rats. These results suggest that blocking 5-HT2A receptor activity has a very limited action to reduce alcohol-seeking. Activating 5-HT2C receptors had a broader behavioural profile to reduce alcohol self-administration, alcohol drinking and alcohol seeking. These effects may partly result from a blunting of the effect of alcohol on mesolimbic DA release.

Exposure to an enriched environment reduces alcohol self-administration in Sardinian alcohol-preferring rats

Living in an enriched environment (EE) produces a notable impact on several rodent behaviors, including those motivated by drugs of abuse. This picture is somewhat less clear when referring to alcohol-motivated behaviors. With the intent of contributing to this research field with data from one of the few rat lines selectively bred for excessive alcohol consumption, the present study investigated the effect of EE on operant oral alcohol self-administration in Sardinian alcohol-preferring (sP) rats. Starting from Postnatal Day (PND) 21, male sP rats were kept under 3 different housing conditions: impoverished environment (IE; single housing in shoebox-like cages with no environmental enrichment); standard environment (SE; small colony cages with 3 rats and no environmental enrichment); EE (large colony cages with 6 rats and multiple elements of environmental enrichment, including 2 floors, ladders, maze, running wheels, and shelter). From PND 60, rats were exposed to different phases of shaping and training of alcohol self-administration. IE, SE, and EE rats were then compared under (i) fixed ratio (FR) 4 (FR4) schedule of alcohol reinforcement for 20 daily sessions and (ii) progressive ratio (PR) schedule of alcohol reinforcement in a final single session. Acquisition of the lever-responding task (shaping) was slower in EE than IE and SE rats, as the likely consequence of a “devaluation” of the novel stimuli provided by the operant chamber in comparison to those to which EE rats were continuously exposed in their homecage or an alteration, induced by EE, of the rat “emotionality” state when facing the novel environment represented by the operant chamber. Training of alcohol self-administration was slower in EE than IE rats, with SE rats displaying intermediate values. A similar ranking order (IE>SE>EE) was also observed in number of lever-responses for alcohol, amount of self-administered alcohol, and breakpoint for alcohol under FR4 and PR schedules of reinforcement. These data suggest that living in a complex environment reduced the reinforcing and motivational properties of alcohol in sP rats. These results are interpreted in terms of the reinforcing and motivational properties of the main components of EE (i.e., social interactions, physical activities, exploration, novelty) substituting, at least partially, for those of alcohol.

RTICBM-74 Is a Brain-Penetrant Cannabinoid Receptor Subtype 1 Allosteric Modulator that Reduces Alcohol Intake in Rats.

The endocannabinoid system is implicated in the neuronal mechanisms of alcohol use disorder (AUD), with the cannabinoid receptor subtype 1 (CB1) representing a promising target for AUD therapeutic interventions. We have previously shown negative allosteric modulators (NAMs) of the CB1 receptor attenuated the reinstatement of other drugs of abuse including cocaine and methamphetamine in rats; however, their effects on alcohol-related behaviors have not been investigated. Here, we tested the pharmacokinetic properties of one such CB1 NAM, RTICBM-74, and its effects on alcohol self-administration in rats. RTICBM-74 showed low aqueous solubility and high protein binding but had excellent half-life and low clearance against rat liver microsomes and hepatocytes, and excellent brain penetrance in rats. RTICBM-74 pretreatment specifically reduced alcohol intake across a range of doses in male or female Wistar or Long-Evans rats that were trained to self-administer alcohol. These effects were similar to the CB1 antagonist/inverse agonist rimonabant, which was tested as a positive control. Importantly, RTICBM-74 was effective at reducing alcohol intake at doses that did not affect locomotion or sucrose self-administration. Our findings suggest that CB1 NAMs such as RTICBM-74 have promising therapeutic potential in treatment of AUD. SIGNIFICANCE STATEMENT: The present work shows that a metabolically stable and brain-penetrant cannabinoid receptor subtype 1 negative allosteric modulator reduces alcohol self-administration in rats without affecting locomotion or sucrose self-administration, suggesting potential therapeutic relevance for the treatment of alcohol use disorder.

The Novel Positive Allosteric Modulator of the GABAB Receptor, KK-92A, Suppresses Alcohol Self-Administration and Cue-Induced Reinstatement of Alcohol Seeking in Rats.

Positive allosteric modulators (PAMs) of the GABAB receptor (GABAB PAMs) are of interest in the addiction field due to their ability to suppress several behaviors motivated by drugs of abuse. KK-92A is a novel GABAB PAM found to attenuate intravenous self-administration of nicotine and reinstatement of nicotine seeking in rats. This present study was aimed at extending to alcohol the anti-addictive properties of KK-92A. To this end, Sardinian alcohol-preferring rats were trained to lever-respond for oral alcohol (15% v/v) or sucrose (0.7% w/v) under the fixed ratio (FR) 5 (FR5) schedule of reinforcement. Once lever-responding behavior had stabilized, rats were exposed to tests with acutely administered KK-92A under FR5 and progressive ratio schedules of reinforcement and cue-induced reinstatement of previously extinguished alcohol seeking. KK-92A effect on spontaneous locomotor activity was also evaluated. Treatment with 10 and 20 mg/kg KK-92A suppressed lever-responding for alcohol, amount of self-administered alcohol, and breakpoint for alcohol. Treatment with 20 mg/kg KK-92A reduced sucrose self-administration. Combination of per se ineffective doses of KK-92A (2.5 mg/kg) and the GABAB receptor agonist, baclofen (1 mg/kg), reduced alcohol self-administration. Treatment with 5, 10, and 20 mg/kg KK-92A suppressed reinstatement of alcohol seeking. Only treatment with 80 mg/kg KK-92A affected spontaneous locomotor activity. These results demonstrate the ability of KK-92A to inhibit alcohol-motivated behaviors in rodents and confirm that these effects are common to the entire class of GABAB PAMs. The remarkable efficacy of KK-92A is discussed in terms of its ago-allosteric properties.

Calcium-permeable AMPA receptor activity and GluA1 trafficking in the basolateral amygdala regulate operant alcohol self-administration.

Addiction is viewed as maladaptive glutamate-mediated neuroplasticity that is regulated, in part, by calcium-permeable AMPA receptor (CP-AMPAR) activity. However, the contribution of CP-AMPARs to alcohol-seeking behavior remains to be elucidated. We evaluated CP-AMPAR activity in the basolateral amygdala (BLA) as a potential target of alcohol that also regulates alcohol self-administration in C57BL/6J mice. Operant self-administration of sweetened alcohol increased spontaneous EPSC frequency in BLA neurons that project to the nucleus accumbens as compared with behavior-matched sucrose controls indicating an alcohol-specific upregulation of synaptic activity. Bath application of the CP-AMPAR antagonist NASPM decreased evoked EPSC amplitude only in alcohol self-administering mice indicating alcohol-induced synaptic insertion of CP-AMPARs in BLA projection neurons. Moreover, NASPM infusion in the BLA dose-dependently decreased the rate of operant alcohol self-administration providing direct evidence for CP-AMPAR regulation of alcohol reinforcement. As most CP-AMPARs are GluA1-containing, we asked if alcohol alters the activation state of GluA1-containing AMPARs. Immunocytochemistry results showed elevated GluA1-S831 phosphorylation in the BLA of alcohol as compared with sucrose mice. To investigate mechanistic regulation of alcohol self-administration by GluA1-containing AMPARs, we evaluated the necessity of GluA1 trafficking using a TET-ON AAV encoding a dominant-negative GluA1 c-terminus (GluA1ct) that blocks activity-dependent synaptic delivery of native GluA1-containing AMPARs. GluA1ct expression in the BLA reduced alcohol self-administration with no effect on sucrose controls. These results show that CP-AMPAR activity and GluA1 trafficking in the BLA mechanistically regulate the reinforcing effects of sweetened alcohol. Pharmacotherapeutic targeting these mechanisms of maladaptive neuroplasticity may aid medical management of alcohol use disorder.

Glucocorticoid receptor modulators decrease alcohol self-administration in male rats

Alcohol use disorder (AUD) is associated with the dysregulation of brain stress and reward systems, including glucocorticoid receptors (GRs). The mixed glucocorticoid/progesterone receptor antagonist mifepristone and selective GR antagonist CORT113176 have been shown to selectively reduce alcohol consumption in alcohol-dependent rats. Mifepristone has also been shown to decrease alcohol consumption and craving for alcohol in humans with AUD. The present study tested the effects of the GR modulators CORT118335, CORT122928, CORT108297, and CORT125134 on alcohol self-administration in nondependent (air-exposed) and alcohol-dependent (alcohol vapor-exposed) adult male rats. Different GR modulators recruit different GR-associated transcriptional cofactors. Thus, we hypothesized that these GR modulators would vary in their effects on alcohol drinking. CORT118335, CORT122928, and CORT125134 significantly reduced alcohol self-administration in both alcohol-dependent and nondependent rats. CORT108297 had no effect on alcohol self-administration in either group. The present results support the potential of GR modulators for the development of treatments for AUD. Future studies that characterize genomic and nongenomic effects of these GR modulators will elucidate potential molecular mechanisms that underlie alcohol drinking in alcohol-dependent and nondependent states.

Central amygdala mineralocorticoid receptors modulate alcohol self-administration

The mineralocorticoid receptor (MR) is an emerging target in the field of alcohol research. The MR is a steroid receptor in the same family as the glucocorticoid receptor, with which it shares the ligand corticosterone in addition to the MR selective ligand aldosterone. Recent studies have shown correlations between central amygdala (CeA) MR expression and alcohol drinking in rats and macaques, as well as correlations between aldosterone and alcohol craving in individuals with alcohol use disorder (AUD). Additionally, our previous work demonstrated that systemic treatment with the MR antagonist spironolactone reduced alcohol self-administration and response persistence in both male and female rats. This study examined if reductions in self-administration following MR antagonist treatment were related to dysregulation of MR-mediated corticosterone negative feedback. Female rats treated with spironolactone (50 mg/kg; IP) showed increased plasma corticosterone following self-administration, which correlated with reduced alcohol self-administration. Next, local microinjection of the MR-selective antagonist eplerenone was used to identify the brain-regional locus of MR action on alcohol self-administration. Eplerenone infusion produced dose-dependent reductions in alcohol self-administration in the CeA, but had no effect in the dorsal hippocampus. Finally, to assay the functional role of CeA MR expression in alcohol self-administration, CeA MR was knocked down by antisense oligonucleotide (ASO) infusion prior to alcohol self-administration. Rats showed a transient reduction in alcohol self-administration 1 day after ASO infusion. Together these studies demonstrate a functional role of CeA MR in modulating alcohol self-administration and make a case for studying MR antagonists as a novel treatment for AUD.

Glucagon-Like Peptide-1 Receptor Signaling in the Ventral Tegmental Area Reduces Alcohol Self-Administration in Male Rats.

The misuse and abuse of alcohol is a major public health issue. However, available treatments are limited with variable efficacy. Recently, preclinical studies show that glucagon-like-peptide-1 (GLP-1) and its analogue Exendin-4 (Ex4) potently reduce a range of alcohol intake behaviors, thus highlighting its potential as a treatment for alcohol use disorders. However, the neural mechanisms and sites of action mediating the effects of Ex4 on alcohol intake behaviors remain to be characterized. This study examined the ventral tegmental area (VTA) as a site of action for the effects of GLP-1 on alcohol intake. Male Long-Evans rats were given intermittent access to 20% alcohol and trained to nose poke for 20% alcohol. Rats received intra-VTA injections of Ex4 (vehicle, 0.01, 0.05μg), and the effects of VTA Ex4 on alcohol self-administration, motivation, and relapse were assessed. When compared to vehicle treatment, intra-VTA Ex4 (0.01, 0.05μg) delivery significantly reduced alcohol self-administration, an effect that was particularly prominent in high alcohol drinkers. However, VTA Ex4 did not reduce reacquisition of alcohol self-administration after extinction nor the motivation to obtain alcohol. Importantly, the lower dose of Ex4 (0.01μg) used had no effect on food intake or locomotor activity, suggesting that the reduction in alcohol self-administration observed was not secondary to caloric intake or motor deficits. Together, these findings provide support for the VTA as a key site of action for GLP-1 on alcohol self-administration but not the reacquisition of alcohol self-administration or motivation to work for alcohol.

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

BackgroundAlcohol 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. MethodsWe 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. ResultsWe 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. ConclusionsCollectively, 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.

Sex differences in the long-term effects of past stress on alcohol self-administration, glucocorticoid sensitivity and phosphodiesterase 10A expression

Stress responses differ by sex, and females are more susceptible to developing mental illnesses because of past stress, including alcohol use disorder. Investigation of neuroadaptations governing the interaction between past stress and future alcohol intake remains understudied in females. A history of footshock stress previously was shown to increase alcohol self-administration under relapse-like conditions in male rats, associated with elevated phosphodiesterase 10A (PDE10A) mRNA expression in the dorsomedial prefrontal cortex and basolateral amygdala. To identify sex differences in long-term stress effects, male and female Wistar rats were exposed to light-cued footshock stress prior to alcohol self-administration training. While past stress did not alter acquisition or extinction, reacquisition self-administration was oppositely impacted by past stress. Stress history slightly increased reacquisition self-administration in males, but reduced alcohol self-administration in females, relative to same-sex controls. Control females self-administered less alcohol following glucocorticoid receptor inhibition by mifepristone, which did not significantly alter alcohol consumption in the other groups. PDE10A expression in synaptically enriched fractions also differed by sex and stress history in a brain region-specific manner. Females expressed more synaptic PDE10A than males in basolateral amygdala and dorsolateral striatum, regardless of stress history, whereas dorsomedial prefrontal cortex PDE10A protein levels matched group differences in reacquisition drinking, but also were expressed at much lower levels than all other regions examined. Together, these data show stress history differentially impacts alcohol self-administration and PDE10A expression by sex, with control females consuming alcohol in a glucocorticoid receptor-sensitive fashion that may relate to sex differences in PDE10A expression.

The mineralocorticoid receptor antagonist spironolactone reduces alcohol self-administration in female and male rats

Cortisol/corticosterone and the hypothalamic-pituitary-adrenal (HPA) axis serve an important role in modulating alcohol drinking behaviors. To date most alcohol research has focused on the functional involvement of corticosterone and the glucocorticoid receptor (GR), the primary receptor for corticosterone. Recent studies have indicated that the related mineralocorticoid receptor (MR), which binds both corticosterone and aldosterone, may also play a role in alcohol drinking. Therefore, the purpose of the present study was to test the functional role of MR signaling in alcohol self-administration via pharmacological antagonism of the MR with spironolactone. Male and female Long-Evans rats were trained to self-administer a sweetened alcohol solution (15% (v/v) alcohol +2% (w/v) sucrose). The effects of spironolactone (0, 10, 25, 50 mg/kg; IP) were tested on alcohol self-administration and under “probe extinction” conditions to measure the persistence of responding in the absence of the alcohol reinforcer. Parallel experiments in sucrose self-administration trained rats were used to confirm the specificity of spironolactone effects to an alcohol reinforcer. In female rats spironolactone (50 mg/kg) reduced alcohol self-administration and persistence of alcohol responding. In male rats spironolactone (25 and 50 mg/kg) reduced alcohol self-administration, but not persistence of alcohol responding. Spironolactone reduced sucrose intake in female rats only, and locomotion in male and female rats during sucrose self-administration. There was no effect of spironolactone on persistence of sucrose responding. These studies add to growing evidence that the MR is involved in alcohol drinking, while underscoring the importance of studying both male and female animals.

Discovery of a Potent, Selective, and Brain-Penetrant Small Molecule that Activates the Orphan Receptor GPR88 and Reduces Alcohol Intake.

The orphan G-protein-coupled receptor GPR88 is highly expressed in the striatum. Studies using GPR88 knockout mice have suggested that the receptor is implicated in alcohol seeking and drinking behaviors. To date, the biological effects of GPR88 activation are still unknown due to the lack of a potent and selective agonist appropriate for in vivo investigation. In this study, we report the discovery of the first potent, selective, and brain-penetrant GPR88 agonist RTI-13951-33 (6). RTI-13951-33 exhibited an EC50 of 25 nM in an in vitro cAMP functional assay and had no significant off-target activity at 38 GPCRs, ion channels, and neurotransmitter transporters that were tested. RTI-13951-33 displayed enhanced aqueous solubility compared to (1 R,2 R)-2-PCCA (2) and had favorable pharmacokinetic properties for behavioral assessment. Finally, RTI-13951-33 significantly reduced alcohol self-administration and alcohol intake in a dose-dependent manner without effects on locomotion and sucrose self-administration in rats when administered intraperitoneally.