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Rationale: Alcohol use disorder remains a leading cause of preventable deaths, and current treatments have limited efficacy. Glucagon-like peptide 1 (GLP-1) receptor agonists can reduce alcohol drinking in preclinical studies, but mechanisms are still not fully understood, and data in female subjects are scarce. Objectives: To assess whether the GLP-1 receptor agonist exendin-4 could decrease alcohol-seeking behavior in the absence of alcohol consumption or intoxication, to compare the potency and efficacy of exendin-4 in the reduction of alcohol seeking vs. alcohol taking, and to compare effects between male and female mice. Methods: Male and female C57BL/6J mice were trained to self-administer 20% alcohol under an FR 1 schedule of reinforcement. After extinction, systemic exendin-4 (saline, 1.8, and 3.2 μg/kg) was tested in cue-induced reinstatement of alcohol seeking. Effects of exendin-4 on alcohol self-administration were tested in a separate group. Results: Exendin-4 suppressed reinstatement of alcohol seeking to extinction levels, at both doses, in the male mice, but had no effect in the female mice. Both doses of exendin-4 also significantly decreased alcohol self-administration in male mice; females again showed less pronounced effects. Conclusions: In male mice, exendin-4 appeared more effective at suppressing alcohol seeking in the absence of alcohol relative to alcohol self-administration, consistent with modulation of alcohol reward or inhibitory control, rather than satiety or aversive effects of alcohol. We saw marked sex differences with less effect of exendin-4 in female mice, and it will be important to include both sexes in further investigations into GLP-1 receptor agonists. [ABSTRACT FROM AUTHOR]

Rationale: The attraction to alcohol can be greatly increased when it is consumed in a social context. While pro-social interactions can potentiate voluntary alcohol drinking under some conditions, aversive social experience (i.e., social stress) can similarly intensify alcohol consumption. Objective: We sought to determine how exposure to different types of chronic social stress (i.e., intermittent episodes of social defeat or continuous social stress) influences alcohol consumption and the reinforcing effects of alcohol in mice with a history of drinking. Methods: Separate cohorts of male C57BL/6J mice were exposed to either 10 days of continuous or intermittent social defeat stress. In experiment 1, mice were assigned to 20% w/v alcohol consumption in a two-bottle choice protocol both prior to and after exposure to social defeat stress. In a second experiment, mice engaged in an operant response sequence to gain access to alcohol wherein completion of a fixed interval (FI; 5 min) schedule was reinforced with continuous access to alcohol (fixed ratio; FR1) for up to 1.8 g/kg. Alcohol-reinforced responding and subsequent alcohol consumption were assessed daily for 4 weeks prior to the 10-day social stress exposure and for 6-week post-stress. Machine learning was implemented to standardize the analysis of defeat behaviors exhibited by the intruder mouse during confrontation with an attacking resident. Results: In mice with a prior history of alcohol drinking, intermittent episodes of social defeat stress produced a significant increase in 20% EtOH consumption in preference over concurrently available water. This increased intake persisted for at least 6 weeks after the final social stress experience. Intermittently stressed mice also accelerated their anticipatory responding during the fixed interval component of the operant response chain that was reinforced by alcohol. Neither unstressed controls nor mice exposed to continuous social stress exhibited significant increases in alcohol consumption and alcohol reinforcement. Discussion: Episodic social defeat stress promotes the seeking and consumption of alcohol, extending earlier work to alcohol-experienced mice. We hypothesize that intermittent access to alcohol and intermittent episodes of social stress are additive and share common sensitizing neural mechanisms that engender excessive alcohol consumption. [ABSTRACT FROM AUTHOR]

Background: Accumulating clinical evidence suggests that women with prior exposure to adverse childhood experiences are more susceptible to heavy drinking and other health‐related behaviors. Yet, preclinical studies investigating sex‐dependent effects of adolescent adverse social experiences (ASEs) on later alcohol‐seeking behavior are lacking. This is mainly due to the unavailability of valid animal models and a shortage of studies that compare effects in males and females. Therefore, we sought to investigate the sex‐dependent effects of ASE on adult alcohol‐seeking behavior, locomotion, and reward sensitivity in male and female rats. Methods: We recently developed a rat model for childhood/adolescent peer rejection that allows us to study the long‐term consequences of ASEs. Adolescent Wistar rats were reared from postnatal day (pd) 21 to pd 50 either within a group of Fischer 344 rats (ASE) or within a group of Wistar rats (control). Wistar rats housed with Fischer 344 rats do not reciprocate social play in adolescence. This reduced play across adolescence mimics peer rejection and results in chronic dysregulation of social and pain‐related behaviors. We tested adult male and female rats in the reinstatement paradigm for cue‐induced alcohol‐seeking behavior, circadian locomotor activity, and sucrose consumption long after the termination of the peer rejection condition. Results: Peer rejection induced persistent sex‐dependent changes in alcohol cue‐induced reinstatement. Females showed an increased reinstatement effect while peer‐rejected males demonstrated a decrease. Sex differences were observed in locomotor activity or reward sensitivity to sucrose. Conclusions: Peer rejection has long‐lasting sex‐dependent consequences on alcohol‐seeking behavior without affecting locomotion or sweet reward sensitivity. Our results suggest that peer‐rejected female rats represent a vulnerable population in which to study relapse‐like behaviors that are similar to clinical findings, while males seem to buffer the peer rejection effect and demonstrate resilience to later life alcohol‐seeking behaviors, as measured by the reinstatement effect. Finally, we provide a novel approach to investigate the molecular and neurobiological underpinnings of ASEs on alcohol and other drug‐seeking behaviors. [ABSTRACT FROM AUTHOR]

Alcohol addiction is a chronic relapsing brain disease characterized by an impaired ability to stop or control alcohol use despite adverse consequences. A main challenge of addiction treatment is to prevent relapse, which occurs in more than >50% of newly abstinent patients with alcohol disorder within 3 months. In people suffering from alcohol addiction, stressful events, drug‐associated cues and contexts, or re‐exposure to a small amount of alcohol trigger a chain of behaviors that frequently culminates in relapse. In this review, we first present the preclinical models that were developed for the study of alcohol seeking behavior, namely the reinstatement model of alcohol relapse and compulsive alcohol seeking under a chained schedule of reinforcement. We then provide an overview of the neurobiological findings obtained using these animal models, focusing on the role of opioids systems, corticotropin‐release hormone and neurokinins, followed by dopaminergic, glutamatergic, and GABAergic neurotransmissions in alcohol seeking behavior. [ABSTRACT FROM AUTHOR]

Given the significant cost of alcohol use disorder (AUD), identifying risk factors for alcohol seeking represents a research priority. Prominent addiction theories emphasize the role of motivation in the alcohol seeking process, which has largely been studied using preclinical models. In order to bridge the gap between preclinical and clinical studies, this study examined predictors of motivation for alcohol self-administration using a novel paradigm. Heavy drinkers (n = 67) completed an alcohol infusion consisting of an alcohol challenge (target breath alcohol = 60 mg%) and a progressive-ratio alcohol self-administration paradigm (maximum breath alcohol 120 mg%; ratio requirements range = 20-3 139 response). Growth curve modeling was used to predict breath alcohol trajectories during alcohol self-administration. K-means clustering was used to identify motivated (n = 41) and unmotivated (n = 26) self-administration trajectories. The data were analyzed using two approaches: a theory-driven test of a-priori predictors and a data-driven, machine learning model. In both approaches, steeper delay discounting, indicating a preference for smaller, sooner rewards, predicted motivated alcohol seeking. The data-driven approach further identified phasic alcohol craving as a predictor of motivated alcohol self-administration. Additional application of this model to AUD translational science and treatment development appear warranted. [ABSTRACT FROM AUTHOR]

Corticotropin releasing factor ( CRF) is a neuropeptide that plays a key role in behavioral and physiological responses to stress. A large body of animal literature implicates CRF acting at type 1 CRF receptors ( CRFR1) in consumption by alcohol-dependent subjects, stress-induced reinstatement of alcohol seeking, and possibly binge alcohol consumption. These studies have encouraged recent pilot studies of CRFR1 antagonists in humans with alcohol use disorder ( AUD). It was a great disappointment to many in the field that these studies failed to show an effect of these compounds on stress-induced alcohol craving. Here, we examine these studies to explore potential limitations and discuss preclinical and human literature to ask whether CRFR1 is still a valid drug target to pursue for the treatment of AUD. [ABSTRACT FROM AUTHOR]

Rationale: Although striatal dopamine (DA) is important in alcohol abuse, the nature of DA release during actual alcohol drinking is unclear, since drinking includes self-administration of both conditioned flavor stimuli (CS) of the alcoholic beverage and subsequent intoxication, the unconditioned stimulus (US). Objectives: Here, we used a novel self-administration analog to distinguish nucleus accumbens (NAcc) DA responses specific to the CS and US. Methods: Right-handed male heavy drinkers ( n = 26) received three positron emission tomography (PET) scans with the D/D radioligand [C]raclopride (RAC) and performed a pseudo self-administration task that separately administered a flavor CS of either a habitually consumed beer or the appetitive control Gatorade®, concomitant with the US of ethanol intoxication (0.06 g/dL intravenous (IV) administration) or IV saline. Scan conditions were Gatorade flavor + saline (Gat&Sal), Gatorade flavor + ethanol (Gat&Eth), and beer flavor + ethanol (Beer&Eth). Results: Ethanol (US) reduced RAC binding (inferring DA release) in the left (L) NAcc [Gat&Sal > Gat&Eth]. Beer flavor (CS) increased DA in the right (R) NAcc [Gat&Eth > Beer&Eth]. The combination of beer flavor and ethanol (CS + US), [Gat&Sal > Beer&Eth], induced DA release in bilateral NAcc. Self-reported intoxication during scanning correlated with L NAcc DA release. Relative to saline, infusion of ethanol increased alcoholic drink wanting. Conclusions: Our findings suggest lateralized DA function in the NAcc, with L NAcc DA release most reflecting intoxication, R NAcc DA release most reflecting the flavor CS, and the conjoint CS + US producing a bilateral NAcc response. [ABSTRACT FROM AUTHOR]

Rationale: Cross-sectional research demonstrates that heavy drinking is associated with elevated impulsivity, including disinhibition. However, causal effects of disinhibition on drinking behaviour are not well established. Objective: To experimentally manipulate disinhibited versus restrained mental sets before exploring their impact on alcohol-seeking behaviour and to investigate if any effects of the manipulation occurred independently of arousal, mood, and craving. Methods: The study utilized a between-subjects design in which participants were randomly allocated to experimental groups. Social drinkers ( N = 90) attended the laboratory for a single session where they initially completed a stop-signal task. Different mental sets were induced by emphasising either the importance of cautious responding and successful inhibition (Restraint group), the importance of rapid responding (Disinhibition group), or the equal importance of rapid responding and successful inhibition (Control group). Heart rate, blood pressure, and subjective mood were assessed before participants completed a bogus taste test procedure. Results: The Restraint group consumed less beer than the Disinhibition and Control groups, which did not differ from each other. There were no group differences in heart rate, blood pressure, or self-reported mood after the manipulation. Across the whole sample, cautious responding during the stop-signal task (slower reaction time to 'Go' cues, fewer inhibition errors) was associated with reduced beer consumption. Conclusions: These findings suggest that temporary fluctuations in disinhibited/restrained states may play a causal role in drinking behaviour. [ABSTRACT FROM AUTHOR]

Reinstatement of responding to a previously alcohol-associated lever following extinction is an established model of relapse-like behavior and can be triggered by stress exposure. Here, we examined whether neuropeptide Y (NPY), an endogenous anti-stress mediator, blocks reinstatement of alcohol-seeking induced by the pharmacological stressor yohimbine. NPY [5.0 or 10.0 μg/rat, intracerebroventricularly (ICV)] dose-dependently blocked the reinstatement of alcohol seeking induced by yohimbine (1.25 mg/kg, i.p.) but failed to significantly suppress the maintenance of alcohol self-administration. We then used c-fos expression mapping to examine neuronal activation following treatment with yohimbine or NPY alone or yohimbine following NPY pre-treatment. The analysis was focused on a network of structures previously implicated in yohimbine-induced reinstatement, comprised of central (CeA) and basolateral (BLA) amygdala and the shell of the nucleus accumbens (Nc AccS). Within this network, both yohimbine and NPY potently induced neuronal activation, and their effects were additive, presumably indicating activation of excitatory and inhibitory neuronal populations, respectively. These results suggest that NPY selectively suppresses relapse to alcohol seeking induced by stressful events and support the NPY system as an attractive target for the treatment of alcohol addiction. [ABSTRACT FROM AUTHOR]

Alcohol-related cues may induce relapse to heavy alcohol drinking and promote molecular adaptations in discrete brain regions. An exact nature of these molecular alterations is still unknown. In the present study, rats trained to self-administer ethanol were tested for cue-induced reinstatement of ethanol seeking after 30 days of abstinence. Next, a detailed immunocytochemical analysis of c-Fos activation was performed within seven nuclei of the amygdala. In the second experiment, c-Fos activation after reinstatement of ethanol seeking induced by discrete cues was compared with the activation pattern of its putative partner (c-Jun) and regulators (extracellular signal-regulated kinases and c-Jun N-terminal kinases). Reexposure to ethanol-associated context cues (an extinction session) potentiated c-Fos expression within the basolateral and central amygdala. Repeated presentation of ethanol-associated discrete cues in an extinction/reinstatement session led to even stronger c-Fos activation in the latter nuclei. In the second experiment, reexposure to the ethanol-associated context and discrete cues activated both c-Jun and extracellular signal-regulated kinases (ERK1/2) in the basolateral amygdala. Our observations suggest that the basolateral and central amygdala may be specifically involved in alcohol-seeking behavior induced by discrete cues.Neuropsychopharmacology (2008) 33, 1835–1846; doi:10.1038/sj.npp.1301567; published online 12 September 2007 [ABSTRACT FROM AUTHOR]

Despite the generally held view that alcohol is an unspecific pharmacological agent, recent molecular pharmacology studies demonstrated that alcohol has only a few known primary targets. These are the NMDA, GABA(A), glycine, 5-hydroxytryptamine 3 (serotonin) and nicotinic ACh receptors as well as L-type Ca(2+) channels and G-protein-activated inwardly rectifying K(+) channels. Following this first hit of alcohol on specific targets in the brain, a second wave of indirect effects on a variety of neurotransmitter/neuropeptide systems is initiated that leads subsequently to the typical acute behavioural effects of alcohol, ranging from disinhibition to sedation and even hypnosis, with increasing concentrations of alcohol. Besides these acute pharmacodynamic aspects of alcohol, we discuss the neurochemical substrates that are involved in the initiation and maintenance phase of an alcohol drinking behaviour. Finally, addictive behaviour towards alcohol as measured by alcohol-seeking and relapse behaviour is reviewed in the context of specific neurotransmitter/neuropeptide systems and their signalling pathways. The activity of the mesolimbic dopaminergic system plays a crucial role during the initiation phase of alcohol consumption. Following long-term, chronic alcohol consumption virtually all brain neurotransmission seems to be affected, making it difficult to define which of the systems contributes the most to the transition from controlled to compulsive alcohol use. However, compulsive alcohol drinking is characterized by a decrease in the function of the reward neurocircuitry and a recruitment of antireward/stress mechanisms comes into place, with a hypertrophic corticotropin-releasing factor system and a hyperfunctional glutamatergic system being the most important ones. [ABSTRACT FROM AUTHOR]

Background The current study examined the effects of ethanol (EtOH) drinking during periadolescence on the subsequent acquisition and extinction of operant self-administration of EtOH and expression of alcohol-seeking behavior in adult alcohol-preferring (P) rats to test the hypothesis that alcohol drinking during periadolescence produces enduring alterations that enhance the reinforcing properties of EtOH. Methods Periadolescent female P rats were given 24 hr free-choice access to 15% (v/v) EtOH starting at postnatal day (PND) 30 and ending on PND 60 or were similarly housed and received water only. On PND 75, without any prior training, periadolescent alcohol-drinking and periadolescent alcohol-naïve rats were placed in standard two-lever (15% EtOH and water) chambers to examine acquisition of EtOH self-administration with a fixed ratio (FR) 1 schedule of reinforcement. After the acquisition phase and after stable responding was established on an FR5 for EtOH and FR1 for water, P rats underwent extinction training for both EtOH and water rewards. After extinction training and a 2 week home cage period, rats were returned to the operant chambers in the absence of reward for seven consecutive sessions (Pavlovian spontaneous recovery). After this testing period, animals were maintained in their home cage for a week before being returned to the operant chambers and allowed to respond for EtOH and water (reacquisition). Results Compared with periadolescent alcohol-naïve rats, periadolescent alcohol-drinking rats acquired EtOH responding sooner (i.e., in the first acquisition session), displayed a greater resistance to extinguish EtOH responding (i.e., higher levels of responding in sessions 4-6), had higher responding for more sessions on the EtOH lever in the absence of reward after a prolonged home cage rest period, and had a more prolonged elevated level of EtOH responding during reacquisition (four sessions versus one session). Conclusions Overall, the results suggest that periadolescent EtOH drinking by P rats produced long-lasting alterations in the reinforcing effects of alcohol, which increased the likelihood that alcohol drinking would be initiated in adulthood, decreased the likelihood that once adult alcohol drinking began it could be extinguished easily, and increased the potential for relapse. [ABSTRACT FROM AUTHOR]