Role of novelty and ethanol history in locomotor stimulation induced by binge-like ethanol intake

Identification of Phosphodiesterase-7A (PDE7A) as a Novel Target for Reducing Ethanol Consumption in Mice

BACKGROUND

Ethanol elicits a rapid stimulatory effect and a subsequent, prolonged sedative response, which are potential predictors of EtOH consumption by decreasing adenosine signaling; this phenomenon also reflects the obvious sex difference. cAMP (cyclic Adenosine Monophosphate)-PKA (Protein Kinase A) signaling pathway modulation can influence the stimulatory and sedative effects induced by EtOH in mice. This study's objective is to clarify the role of phosphodiesterase (PDE) in mediating the observed sex differences in EtOH responsiveness between male and female animals.

METHODS

EtOH was administered i.p. for 7 days to identify the changes in PDE isoforms in response to EtOH treatment. Additionally, EtOH consumption and preference of male and female C57BL/6J mice were assessed using the drinking-in-the-dark and 2-bottle choice tests. Further, pharmacological inhibition of PDE7A heterozygote knockout mice was performed to investigate its effects on EtOH-induced stimulation and sedation in both male and female mice. Finally, Western blotting analysis was performed to evaluate the alterations in cAMP-PKA/Epac2 pathways.

RESULTS

EtOH administration resulted in an immediate upregulation in PDE7A expression in female mice, indicating a strong association between PDE7A and EtOH stimulation. Through the pharmacological inhibition of PDE7A KD mice, we have demonstrated for the first time, to our knowledge, that PDE7A selectively attenuates EtOH responsiveness and consumption exclusively in female mice, whichmay be associated with the cAMP-PKA/Epac2 pathway and downstream phosphorylation of CREB and ERK1/2.

CONCLUSIONS

Inhibition or knockdown of PDE7A attenuates EtOH responsivenessand consumption exclusively in female mice, which is associated with alterations in the cAMP-PKA/Epac2 signaling pathways, thereby highlighting its potential as a novel therapeutic target for alcohol use disorder.

Systemic administration of racemic baclofen reduces both acquisition and maintenance of alcohol consumption in male and female mice

Baclofen is a GABAB receptor agonist with proposed use as a treatment for alcohol use disorder (AUD). In preclinical studies, racemic baclofen decreases alcohol consumption in both mice and rats; however, there is a significant disparity in the efficacy of the drug across species. We previously demonstrated that baclofen is enantioselective, with the racemic enantiomer successfully reducing binge-like alcohol consumption during Drinking-in-the-Dark (DID) in C57BL/6J (B6) mice, as well as 24-h consumption during two-bottle choice (2BC) preference drinking in replicate 1 High Alcohol Preferring (HAP) mice. Here we extend these findings by investigating the effects of racemic baclofen on the acquisition and maintenance of alcohol consumption, locomotor activity, and saccharin drinking in two different mouse genotypes and drinking paradigms. Adult male and female B6 mice were allowed free access to 20% (v/v) alcohol for 2 h daily in a 14-day DID procedure. Adult male and female replicate 2 HAP (HAP2) mice were allowed 24-h access to 10% (v/v) alcohol versus tap water in a 2BC procedure for 14 days. Systemic injections of baclofen (0.0 or 3.0 mg/kg) were given 3 h into the dark cycle on days 1-5 in alcohol acquisition experiments and days 6-10 in alcohol maintenance experiments. We found that racemic baclofen significantly reduces acquisition of DID and 2BC alcohol drinking in male and female B6 and HAP2 mice, whereas it only significantly reduces the maintenance of DID alcohol intake in B6 mice. Racemic baclofen did not alter home cage locomotor activity but did alter saccharin intake, suggesting it may have nonspecific effects. The current data add to literature suggesting that smaller doses of racemic baclofen may be an effective treatment of AUD. Future work should focus on the longitudinal efficacy of racemic baclofen in high-drinking mouse genotypes to further investigate whether it is effective for those with a genetic predisposition to AUD.

The development, but not expression, of alcohol front-loading in C57BL/6J mice maintained on LabDiet 5001 is abolished by maintenance on Teklad 2920x rodent diet

BACKGROUND

Excessive alcohol (ethanol) consumption, such as binge drinking, is extremely commonplace and represents a major health concern. Through modeling excessive drinking in rodents, we are beginning to uncover the neurobiological and neurobehavioral causes and consequences of this pattern of ethanol intake. One important factor for modeling binge drinking in mice is that they reliably drink to blood ethanol concentrations (BECs) of 80 mg/dl or higher. Drinking-in-the-dark (DID) is a commonly used mouse model of binge drinking, and we have shown that this method reliably results in robust ethanol front-loading and binge-level BECs in C57BL/6J (B6) mice and other ethanol-preferring mouse strains/lines. However, establishing the DID model in a new vivarium space forced us to consider the use of rodent diet formulations that we had not previously used.

METHODS

The current set of experiments were designed to investigate the role of two standard rodent diet formulations on binge drinking and the development of ethanol front-loading using DID.

RESULTS

We found that BECs in animals maintained on LabDiet 5001 (LD01) were double those found in mice maintained on Teklad 2920x (TL20). Interestingly, this effect was paralleled by differences in the degree of front-loading, such that LD01-fed mice consumed approximately twice as much ethanol in the first 15 min of the 2-h DID sessions as the TL20-fed mice. Surprisingly, however, mice that developed front-loading during maintenance on the LD01 diet continued to display front-loading behavior after being switched to the TL20 diet.

CONCLUSIONS

These data emphasize the importance of choosing and reporting diet formulations when conducting voluntary drinking studies and support the need for further investigation into the mechanisms behind diet-induced differences in binge drinking, particularly front-loading.

Sleep, sleep homeostasis and arousal disturbances in alcoholism

The effects of alcohol on human sleep were first described almost 70 years ago. Since then, accumulating evidences suggest that alcohol intake at bed time immediately induces sleep [reduces the time to fall asleep (sleep onset latency), and consolidates and enhances the quality (delta power) and the quantity of sleep]. Such potent sleep promoting activity makes alcohol as one of the most commonly used "over the counter" sleep aid. However, the somnogenic effects, after alcohol intake, slowly wane off and often followed by sleep disruptions during the rest of the night. Repeated use of alcohol leads to the development of rapid tolerance resulting into an alcohol abuse. Moreover, chronic and excessive alcohol intake leads to the development of alcohol use disorder (AUD). Alcoholics, both during drinking periods and during abstinences, suffer from a multitude of sleep disruptions manifested by profound insomnia, excessive daytime sleepiness, and altered sleep architecture. Furthermore, subjective and objective indicators of sleep disturbances are predictors of relapse. Finally, within the USA, it is estimated that societal costs of alcohol-related sleep disorders exceed $18 billion. Thus, although alcohol associated sleep problems have significant economic and clinical consequences, very little is known about how and where alcohol acts to affect sleep. In this review, a conceptual framework and clinical research focused on understanding the relationship between alcohol and sleep is first described. In the next section, our new and exciting preclinical studies, to understand the cellular and molecular mechanism of how acute and chronic alcohol affects sleep, are described. In the end, based on observations from our recent findings and related literature, opportunities for the development of innovative strategies to prevent and treat AUD are proposed.

Assessment of Acute Motor Effects and Tolerance Following Self-Administration of Alcohol and Edible ∆9 -Tetrahydrocannabinol in Adolescent Male Mice

BACKGROUND

Cannabinoids and their principle psychoactive target, the cannabinoid type 1 receptor (CB1R), impact a number of alcohol-related properties, and although alcohol and cannabis are often co-used, particularly in adolescence, few animal models of this phenomenon exist. We modeled the co-use of alcohol and ∆⁹ -tetrahydrocannabinol (THC) in adolescent mice using ingestive methods popular during this developmental period in humans, namely binge-drinking and edible THC. With this model, we assessed levels of use, acute effects, and tolerance to each substance.

METHODS

Adolescent male C57BL/6J mice had daily, limited access to 1 of 2 edible doughs (THC or control), to 1 of 2 fluids (ethanol (EtOH) or water), and in 1 of 2 orders (dough-fluid or fluid-dough). Home cage locomotor activity was recorded both during access and after access. On the day following the final access session, a subset of mice were assessed for functional and metabolic tolerance to alcohol using accelerating rotarod and blood EtOH concentrations, respectively. The remaining mice were assessed for tolerance to THC-induced hypothermia, and whole-brain CB1R expression was assessed in all mice.

RESULTS

EtOH intake was on par with levels previously reported in adolescent mice. Edible THC was well-consumed, but consumption decreased at the highest dose provided. Locomotor activity increased following EtOH intake and decreased following edible THC consumption, and edible THC increased fluid intake in general. The use of alcohol produced neither functional nor metabolic tolerance to an alcohol challenge. However, the use of edible THC impaired subsequent drug-free rotarod performance and was associated with a reduction in THC's hypothermic effect.

CONCLUSIONS

Adolescent mice self-administered both alcohol and edible THC to a degree sufficient to acutely impact locomotor activity. However, only edible THC consumption had lasting effects during short-term abstinence. Thus, this adolescent co-use model could be used to explore sex differences in self-administration and the impact substance co-use might have on other domains such as mood and cognition.

Self-administration of edible Δ9-tetrahydrocannabinol and associated behavioral effects in mice

BACKGROUND

With increasing access to legal cannabis across the globe, it is imperative to more closely study its behavioral and physiological effects. Furthermore, with the proliferation of cannabis use, modes of consumption are changing, with edible formulations becoming increasingly popular. Nevertheless, there are relatively few animal models of self-administration of the primary psychoactive component of cannabis, Δ⁹-tetrahydrocannabinol (THC), and almost all incorporate routes of administration other than those used by humans. The aim of the current study was to develop a model of edible THC self-administration and assess its impact on CB1 receptor-mediated behaviors in female and male mice.

METHODS

Mice were given limited access to a palatable dough which occasionally contained THC in doses ranging from 1 to 10 mg/kg. Following dough consumption, mice were assessed for home cage locomotor activity, body temperature, or analgesia. Locomotor activity was also assessed in conjunction with the CB1 receptor antagonist SR141716A.

RESULTS

Dough was well-consumed, but consumption decreased at the highest THC concentrations. Edible THC produced dose-dependent decreases in locomotor activity and body temperature in both sexes, and these effects were more pronounced in male mice. Hypolocomotion induced by edible THC was attenuated by SR141716A, indicating mediation by CB1 receptor activation.

CONCLUSIONS

In contrast to other cannabinoid self-administration models, edible THC is relatively low in stress and uses a route of administration analogous to one used by humans. Potential applications include chronic THC self-administration, determining THC reward/reinforcement, and investigating consequences of oral THC use.

Activation of extrasynaptic δ-GABAA receptors globally or within the posterior-VTA has estrous-dependent effects on consumption of alcohol and estrous-independent effects on locomotion

Recent reports support higher than expected rates of binge alcohol consumption among women and girls. Unfortunately, few studies have assessed the mechanisms underlying this pattern of intake in females. Studies in males suggest that alcohol concentrations relevant to the beginning stages of binge intoxication may selectively target tonic GABAergic inhibition mediated by GABAA receptor subtypes expressing the δ-subunit protein (δ-GABAARs). Indeed, administration of agonists that interact with these δ-GABAARs prior to alcohol access can abolish binge drinking behavior in male mice. These δ-GABAARs have also been shown to exhibit estrous-dependent plasticity in regions relevant to drug taking behavior, like the hippocampus and periaqueductal gray. The present experiments were designed to determine whether the estrous cycle would alter binge drinking, or our ability to modulate this pattern of alcohol use with THIP, an agonist with high selectivity and efficacy at δ-GABAARs. Using the Drinking-in-the-Dark (DID) binge-drinking model, regularly cycling female mice were given 2h of daily access to alcohol (20%v/v). Vaginal cytology or vaginal impedance was assessed after drinking sessions to track estrous status. There was no fluctuation in binge drinking associated with the estrous cycle. Both Intra-posterior-VTA administration of THIP and systemic administration of the drug was also associated with an estrous cycle dependent reduction in drinking behavior. Pre-treatment with finasteride to inhibit synthesis of 5α-reduced neurosteroids did not disrupt THIP's effects. Analysis of δ-subunit mRNA from posterior-VTA enriched tissue samples revealed that expression of this GABAA receptor subunit is elevated during diestrus in this region. Taken together, these studies demonstrate that δGABAARs in the VTA are an important target for binge drinking in females and confirm that the estrous cycle is an important moderator of the pharmacology of this GABAA receptor subtype.

Concomitant Caffeine Increases Binge Consumption of Ethanol in Adolescent and Adult Mice, But Produces Additive Motor Stimulation Only in Adolescent Animals

BACKGROUND

Binge co-consumption of highly caffeinated energy drinks with alcohol (ethanol [EtOH]) has become a common practice among adolescents/young adults and has been associated with an increased incidence of hazardous behaviors. Animal models are critical in advancing our understanding the neurobehavioral consequences of this form of binge drinking. Surprisingly, virtually no work has explored caffeine and EtOH co-consumption or its long-term consequences in adolescent animals. The primary objective of the current study was to extend a previously established mouse model of voluntary binge caffeine and EtOH co-consumption to explore adolescent consumption and responses compared to adults.

METHODS

Adolescent and adult male C57BL/6J mice had daily limited access to caffeine (0.03% w/v), EtOH (20% v/v), a combined EtOH/caffeine solution, or water for 14 days via the binge-like drinking paradigm, drinking-in-the-dark (DID). Home cage locomotor activity was measured during DID in a subset of mice. Following DID, all mice rested for 18 days so that adolescents reached adulthood, whereupon all mice underwent 7 days of continuous access 2-bottle choice drinking for 10% (v/v) EtOH or water.

RESULTS

Co-consumption with caffeine significantly increased EtOH intake and resultant blood ethanol concentrations in both adolescent and adult mice. In addition, adolescent mice exhibited a uniquely robust locomotor stimulant response to caffeine and EtOH co-consumption. Later EtOH intake and preference was not influenced, however, by prior fluid consumption history via DID.

CONCLUSIONS

Together with findings from the human literature, our results suggest that caffeine co-consumption may positively influence binge alcohol consumption in adolescents/young adults. Importantly, this age group may be particularly sensitive to the additive stimulant effects of caffeinated alcohol consumption, an effect which may be related to the high incidence of associated negative outcomes in this population. These observations are particularly concerning considering the heightened plasticity of the adolescent brain.

Relative fluid novelty differentially alters the time course of limited-access ethanol and water intake in selectively bred high-alcohol-preferring mice

BACKGROUND

The influence of previous alcohol (ethanol [EtOH])-drinking experience on increasing the rate and amount of future EtOH consumption might be a genetically regulated phenomenon critical to the development and maintenance of repeated excessive EtOH abuse. We have recently found evidence supporting this view, wherein inbred C57BL/6J (B6) mice develop progressive increases in the rate of binge EtOH consumption over repeated drinking-in-the-dark (DID) EtOH access sessions (i.e., "front loading"). The primary goal of this study was to evaluate identical parameters in high-alcohol-preferring (HAP) mice to determine whether similar temporal alterations in limited-access EtOH drinking develop in a population selected for high EtOH preference/intake under continuous (24-hour) access conditions.

METHODS

Using specialized volumetric drinking devices, HAP mice received 14 daily 2-hour DID EtOH or water access sessions. A subset of these mice was then given 1 day access to the opposite assigned fluid on day 15. Home cage locomotor activity was recorded concomitantly on each day of these studies. The possibility of behavioral/metabolic tolerance was evaluated on day 16 using experimenter-administered EtOH.

RESULTS

The amount of EtOH consumed within the first 15 minutes of access increased markedly over days. However, in contrast to previous observations in B6 mice, EtOH front loading was also observed on day 15 in mice that only had previous DID experience with water. Furthermore, a decrease in the amount of water consumed within the first 15 minutes of access compared to animals given repeated water access was observed on day 15 in mice with 14 previous days of EtOH access.

CONCLUSIONS

These data further illustrate the complexity and importance of the temporal aspects of limited-access EtOH consumption and suggest that previous procedural/fluid experience in HAP mice selectively alters the time course of EtOH and water consumption.

Involvement of the GABAA Receptor in Age-Dependent Differences in Binge-Like Ethanol Intake

BACKGROUND

Binge alcohol (ethanol [EtOH]) drinking is common during adolescence, a time characterized by many behavioral and neurobiological changes. Among them, the GABAA receptor system undergoes substantial modifications, including changes in the density, distribution, and subunit composition of the receptor. Based on its demonstrated role in EtOH consumption, this study aimed to investigate the effects of 2 different GABAA receptor agonists on binge-like EtOH intake in adolescent and adult mice using the Drinking-in-the-Dark model.

METHODS

Three hours into their dark cycle, adolescent (postnatal day 28 [P28]) and adult (P63) male C57BL/6J mice were given daily access to 20% EtOH for 2 hours during 8 consecutive days. Immediately before the access on day 8, mice (P35 and P70) were systemically injected with 1 of 2 different GABAergic drugs. The effects of muscimol, a full GABAA agonist, were assessed in a first experiment. The second experiment tested for the more specific involvement of δ-containing extrasynaptic GABAA receptors through the administration of THIP (4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol).

RESULTS

Adolescent mice consumed more EtOH than their adult counterparts. Following the administration of GABAA agonists, levels of EtOH intake were reduced at both ages. However, age-dependent differences were revealed following the administration of THIP, with adolescents exhibiting greater sensitivity to its suppressant effects, especially during the first 30 minutes of binge EtOH access.

CONCLUSIONS

This study adds to the existing literature demonstrating the crucial role of the GABAA receptor in alcohol consumption. In addition, it suggests that age differences in the GABAA receptor modulation of binge alcohol drinking might be more dependent on extrasynaptic GABAA receptors.

Adenosinergic regulation of binge-like ethanol drinking and associated locomotor effects in male C57BL/6J mice

We recently observed that the addition of caffeine (a nonselective adenosine receptor antagonist) to a 20% ethanol solution significantly altered the intoxication profile of male C57BL/6J (B6) mice induced by voluntary binge-like consumption in the 'Drinking-in-the-Dark' (DID) paradigm. In the current study, the roles of A1 and A2A adenosine receptor subtypes, specifically, in binge-like ethanol consumption and associated locomotor effects were explored. Adult male B6 mice (PND 60-70) were allowed to consume 20% ethanol (v/v) or 2% sucrose (w/v) for 6days via DID. On day 7, mice received a systemic administration (i.p.) of the A1 antagonist DPCPX (1, 3, 6mg/kg), the A2A antagonist MSX-3 (1, 2, 4mg/kg), or vehicle immediately prior to fluid access in DID. Antagonism of the A1 receptor via DPCPX was found to dose-dependently decrease binge-like ethanol intake and associated blood ethanol concentrations (p's<0.05), although no effect was observed on sucrose intake. Antagonism of A2A had no effect on ethanol or sucrose consumption, however, MSX-3 elicited robust locomotor stimulation in mice consuming either solution (p's<0.05). Together, these findings suggest unique roles for the A1 and A2A adenosine receptor subtypes in binge-like ethanol intake and its associated locomotor effects.

Alterations in the rate of binge ethanol consumption: implications for preclinical studies in mice

The rate at which alcohol (ethanol) is consumed has direct impact on its behavioral and subjective effects. For this reason, alterations in the pattern of ethanol consumption as a function of drinking history might be critical to the development and maintenance of alcoholism. Furthermore, because pharmacological interventions aimed at disrupting the motivation to consume ethanol are dependent on the brain/plasma concentrations present when an individual is most likely to engage in consumption of this substance, characterizing temporal drinking patterns might be useful to determine the timing of such treatments. The primary goal of the present study was to evaluate alterations in the timecourse of daily binge (drinking-in-the-dark; DID) ethanol consumption. We gave 14 daily 2 hour DID ethanol or water access sessions to male C57BL/6J (B6) mice using a state of the art volumetric drinking monitoring device. We then, primarily as a proof-of-principle, used the GABAB allosteric modulator GS39783 (GS) to determine how this compound influenced the timecourse of binge-like ethanol intake. The rate of ethanol consumption increased dramatically over sessions with the majority occurring in the first few minutes of the final session. Additionally, ethanol consumption occurring immediately following access was almost completely abolished in mice pre-treated with GS; an effect which was ethanol-specific only at this early time interval. These data characterize progressive alterations in the rate of ethanol intake using the DID model and suggest that careful consideration of prior ethanol history and timing of drug administration are warranted when interpreting results of pre-clinical drug administration studies.

Site-specific microinjection of Gaboxadol into the infralimbic cortex modulates ethanol intake in male C57BL/6J mice

Extrasynaptic GABAA receptors, often identified as those containing both α4 and δ subunits, demonstrate super-sensitivity to GABA and are involved in tonic inhibitory processes regulating activity within mesolimbocortical circuitry. Rodent studies testing the effects of the δ-subunit selective agonist Gaboxadol (THIP) on alcohol consumption have produced mixed results. The goal of this study was to determine the role of extrasynaptic GABAA receptors located in the infralimbic cortex (ILC) in the alcohol consumption of male C57BL/6J (B6) mice. The ILC is of interest due to its demonstrated involvement in stress reactivity. Furthermore, alcohol exposure has been shown to interfere with extinction learning; impairments of which may be related to inflexible behavior (i.e., problematic alcohol consumption). Adult male B6 mice were bilaterally implanted with guide cannulas aimed at the ILC and were subsequently offered daily limited access to 20% ethanol or 5% sucrose for 7 days. Immediately prior to ethanol or sucrose access on day 7, mice were bilaterally injected with 50 or 100ng THIP (25 or 50ng per side respectively) or saline vehicle into the ILC. The highest dose of intra-ILC THIP (100ng/mouse) increased alcohol intake relative to vehicle controls, although control animals consumed relatively little ethanol following infusion. Intra-ILC THIP had no effect on sucrose consumption (p>0.05), suggesting that the effect of THIP was selective for ethanol consumption. Together, these findings suggest that THIP may have effectively prevented the decrease in ethanol intake on day 7 induced by the microinjection process, perhaps supporting a suggested role for the ILC in adaptive learning processes and behavioral flexibility.

"Wired," yet intoxicated: modeling binge caffeine and alcohol co-consumption in the mouse

BACKGROUND

The combination of highly caffeinated "energy drinks" with alcohol (ethanol [EtOH]) has become popular among young adults and intoxication via such beverages has been associated with an elevated risk for harmful behaviors. However, there are discrepancies in the human literature regarding the effect of caffeine on alcohol intoxication, perhaps due to confounding factors such as personality type, expectancy, and history of exposure. Animal models of co-exposure are resistant to such issues; however, the consequences of voluntary co-consumption have been largely ignored in the animal literature. The primary goal of this work was to characterize a mouse model of binge caffeine and EtOH co-consumption employing the limited access "Drinking-in-the-Dark" (DID) paradigm.

METHODS

Caffeine was added to a 20% alcohol solution via DID. Alcohol/caffeine intake, locomotor behavior, ataxia, anxiety-like behavior, and cognitive function were evaluated as a consequence of co-consumption in adult male C57BL/6J mice.

RESULTS

Caffeine did not substantially alter binge alcohol intake or resultant blood EtOH concentrations (BECs), nor did it alter alcohol's anxiolytic effects on the elevated plus maze or cognitive-interfering effects in a novel object-recognition task. However, no evidence of alcohol-induced sedation was observed in co-consumption groups that instead demonstrated a highly stimulated state similar to that of caffeine alone. The addition of caffeine was also found to mitigate alcohol-induced ataxia.

CONCLUSIONS

Taken together, our mouse model indicates that binge co-consumption of caffeine and alcohol produces a stimulated, less ataxic and anxious, as well as cognitively altered state; a state that could be of great public health concern. These results appear to resemble the colloquially identified "wide awake drunk" state that individuals seek via consumption of such beverages. This self-administration model therefore offers the capacity for translationally valid explorations of the neurobiological consequences of binge co-consumption to assess the public health risk of this drug combination.

Repeated binge-like ethanol drinking alters ethanol drinking patterns and depresses striatal GABAergic transmission

Repeated cycles of binge alcohol drinking and abstinence are key components in the development of dependence. However, the precise behavioral mechanisms underlying binge-like drinking and its consequences on striatal synaptic physiology remain unclear. In the present study, ethanol and water drinking patterns were recorded with high temporal resolution over 6 weeks of binge-like ethanol drinking using the 'drinking in the dark' (DID) protocol. The bottle exchange occurring at the beginning of each session prompted a transient increase in the drinking rate that might facilitate the acquisition of ethanol binge-like drinking. Ethanol drinking mice also displayed a 'front-loading' behavior, in which the highest rate of drinking was recorded during the first 15 min. This rate increased over weeks and paralleled the mild escalation of blood ethanol concentrations. GABAergic and glutamatergic transmission in the dorsal striatum were examined following DID. Spontaneous glutamatergic transmission and the density of dendritic spines were unchanged after ethanol drinking. However, the frequency of GABAA receptor-mediated inhibitory postsynaptic currents was depressed in medium spiny neurons of ethanol drinking mice. A history of ethanol drinking also increased ethanol preference and altered the acute ethanol effects on GABAergic transmission differentially in dorsolateral and dorsomedial striatum. Together, the study shows that the bottle exchange during DID promotes fast, voluntary ethanol drinking and that this intermittent pattern of ethanol drinking causes a depression of GABAergic transmission in the dorsal striatum.