Genetically selected alcohol preferring rats to model human alcoholism

Epigenetic Dysregulation in Alcohol-Associated Behaviors: Preclinical and Clinical Evidence

Alcohol use disorder (AUD) is characterized by loss of control over intake and drinking despite harmful consequences. At a molecular level, AUD is associated with long-term neuroadaptations in key brain regions that are involved in reward processing and decision-making. Over the last decades, a great effort has been made to understand the neurobiological basis underlying AUD. Epigenetic mechanisms have emerged as an important mechanism in the regulation of long-term alcohol-induced gene expression changes. Here, we review the literature supporting a role for epigenetic processes in AUD. We particularly focused on the three most studied epigenetic mechanisms: DNA methylation, Histone modification and non-coding RNAs. Clinical studies indicate an association between AUD and DNA methylation both at the gene and global levels. Using behavioral paradigms that mimic some of the characteristics of AUD, preclinical studies demonstrate that changes in epigenetic mechanisms can functionally impact alcohol-associated behaviors. While many studies support a therapeutic potential for targeting epigenetic enzymes, more research is needed to fully understand their role in AUD. Identification of brain circuits underlying alcohol-associated behaviors has made major advances in recent years. However, there are very few studies that investigate how epigenetic mechanisms can affect these circuits or impact the neuronal ensembles that promote alcohol-associated behaviors. Studies that focus on the role of circuit-specific and cell-specific epigenetic changes for clinically relevant alcohol behaviors may provide new insights on the functional role of epigenetic processes in AUD.

Brain Network Allostasis after Chronic Alcohol Drinking Is Characterized by Functional Dedifferentiation and Narrowing

Alcohol use disorder (AUD) causes complex alterations in the brain that are poorly understood. The heterogeneity of drinking patterns and the high incidence of comorbid factors compromise mechanistic investigations in AUD patients. Here we used male Marchigian Sardinian alcohol-preferring (msP) rats, a well established animal model of chronic alcohol drinking, and a combination of longitudinal resting-state fMRI and manganese-enhanced MRI to provide objective measurements of brain connectivity and activity, respectively. We found that 1 month of chronic alcohol drinking changed the correlation between resting-state networks. The change was not homogeneous, resulting in the reorganization of pairwise interactions and a shift in the equilibrium of functional connections. We identified two fundamentally different forms of network reorganization. First is functional dedifferentiation, which is defined as a regional increase in neuronal activity and overall correlation, with a concomitant decrease in preferential connectivity between specific networks. Through this mechanism, occipital cortical areas lost their specific interaction with sensory-insular cortex, striatal, and sensorimotor networks. Second is functional narrowing, which is defined as an increase in neuronal activity and preferential connectivity between specific brain networks. Functional narrowing strengthened the interaction between striatal and prefrontocortical networks, involving the anterior insular, cingulate, orbitofrontal, prelimbic, and infralimbic cortices. Importantly, these two types of alterations persisted after alcohol discontinuation, suggesting that dedifferentiation and functional narrowing rendered persistent network states. Our results support the idea that chronic alcohol drinking, albeit at moderate intoxicating levels, induces an allostatic change in the brain functional connectivity that propagates into early abstinence.SIGNIFICANCE STATEMENT Excessive consumption of alcohol is positioned among the top five risk factors for disease and disability. Despite this priority, the transformations that the nervous system undergoes from an alcohol-naive state to a pathologic alcohol drinking are not well understood. In our study, we use an animal model with proven translational validity to study this transformation longitudinally. The results show that shortly after chronic alcohol consumption there is an increase in redundant activity shared by brain structures, and the specific communication shrinks to a set of pathways. This functional dedifferentiation and narrowing are not reversed immediately after alcohol withdrawal but persist during early abstinence. We causally link chronic alcohol drinking with an early and abstinence-persistent retuning of the functional equilibrium of the brain.

Leveraging Neural Networks in Preclinical Alcohol Research

Alcohol use disorder is a pervasive healthcare issue with significant socioeconomic consequences. There is a plethora of neural imaging techniques available at the clinical and preclinical level, including magnetic resonance imaging and three-dimensional (3D) tissue imaging techniques. Network-based approaches can be applied to imaging data to create neural networks that model the functional and structural connectivity of the brain. These networks can be used to changes to brain-wide neural signaling caused by brain states associated with alcohol use. Neural networks can be further used to identify key brain regions or neural "hubs" involved in alcohol drinking. Here, we briefly review the current imaging and neurocircuit manipulation methods. Then, we discuss clinical and preclinical studies using network-based approaches related to substance use disorders and alcohol drinking. Finally, we discuss how preclinical 3D imaging in combination with network approaches can be applied alone and in combination with other approaches to better understand alcohol drinking.

Translational dynamics of alcohol tolerance of preclinical models and human laboratory studies

Increasing sensitivity due to alcohol intake has been explored using molecular and cellular mechanisms of sensitization and adaptive biobehavioral changes as well as through negative experiences of altered function during withdrawal. However, within both a preclinical and human laboratory setting, little has been elucidated toward understanding the neural substrates of decreased sensitivity to alcohol effects, that is, alcohol tolerance. More paradigms assessing alcohol tolerance are needed. Tolerance can be assessed through both self-reported response (subjective) and observed (objective) measurements. Therefore, sensitivity to alcohol is an exploitable variable that can be utilized to disentangle the diverse alcohol use disorder (AUD) phenotypical profile. This literature review focuses on preclinical models and human laboratory studies to evaluate alcohol tolerance and its modulating factors. Increased understanding of alcohol tolerance has the potential to reduce gaps between preclinical models and human laboratory studies to better evaluate the development of alcohol-related biobehavioral responses. Furthermore, alcohol tolerance can be used as an AUD phenotypic variable in randomized clinical trials designed for developing AUD therapies. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Chronic alcohol consumption alters extracellular space geometry and transmitter diffusion in the brain

Already moderate alcohol consumption has detrimental long-term effects on brain function. However, how alcohol produces its potent addictive effects despite being a weak reinforcer is a poorly understood conundrum that likely hampers the development of successful interventions to limit heavy drinking. In this translational study, we demonstrate widespread increased mean diffusivity in the brain gray matter of chronically drinking humans and rats. These alterations appear soon after drinking initiation in rats, persist into early abstinence in both species, and are associated with a robust decrease in extracellular space tortuosity explained by a microglial reaction. Mathematical modeling of the diffusivity changes unveils an increased spatial reach of extrasynaptically released transmitters like dopamine that may contribute to alcohol's progressively enhanced addictive potency.

Individual Differences in Ethanol Drinking and Seeking Behaviors in Rats Exposed to Chronic Intermittent Ethanol Vapor Exposure is Associated with Altered CaMKII Autophosphorylation in the Nucleus Accumbens Shell

Chronic intermittent ethanol vapor exposure (CIE) in rodents produces reliable and high blood ethanol concentration and behavioral symptoms associated with moderate to severe alcohol use disorder (AUD)—for example, escalation of operant ethanol self-administration, a feature suggestive of transition from recreational to addictive use, is a widely replicated behavior in rats that experience CIE. Herein, we present evidence from a subset of rats that do not demonstrate escalation of ethanol self-administration following seven weeks of CIE. These low responders (LR) maintain low ethanol self-administration during CIE, demonstrate lower relapse to drinking during abstinence and reduced reinstatement of ethanol seeking triggered by ethanol cues when compared with high responders (HR). We examined the blood ethanol levels in LR and HR rats during CIE and show higher levels in LR compared with HR. We also examined peak corticosterone levels during CIE and show that LR rats have higher levels compared with HR rats. Lastly, we evaluated the levels of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) in the nucleus accumbens shell and reveal that the activity of CaMKII, which is autophosphorylated at site Tyr-286, is significantly reduced in HR rats compared with LR rats. These findings demonstrate that dysregulation of the hypothalamic–pituitary–adrenal axis activity and plasticity-related proteins regulating molecular memory in the nucleus accumbens shell are associated with higher ethanol-drinking and -seeking in HR rats. Future mechanistic studies should evaluate CaMKII autophosphorylation-dependent remodeling of glutamatergic synapses in the ventral striatum as a plausible mechanism for the CIE-induced enhanced ethanol drinking and seeking behaviors.

phMRI, neurochemical and behavioral responses to psychostimulants distinguishing genetically selected alcohol-preferring from genetically heterogenous rats

Alcoholism is often associated with other forms of drug abuse, suggesting that innate predisposing factors may confer vulnerability to addiction to diverse substances. However, the neurobiological bases of these factors remain unknown. Here, we have used a combination of imaging, neurochemistry and behavioral techniques to investigate responses to the psychostimulant amphetamine in Marchigian Sardinian (msP) alcohol-preferring rats, a model of vulnerability to alcoholism. Specifically, we employed pharmacological magnetic resonance imaging to investigate the neural circuits engaged by amphetamine challenge, and to relate functional reactivity to neurochemical and behavioral responses. Moreover, we studied self-administration of cocaine in the msP rats. We found stronger functional responses in the extended amygdala, alongside with increased release of dopamine in the nucleus accumbens shell and augmented vertical locomotor activity compared with controls. Wistar and msP rats did not differ in operant cocaine self-administration under short access (2 hours) conditions, but msP rats exhibited a higher propensity to escalate drug intake following long access (6 hours). Our findings suggest that neurobiological and genetic mechanisms that convey vulnerability to excessive alcohol drinking also facilitate the transition from psychostimulants use to abuse.

What Is Addiction? How Can Animal and Human Research Be Used to Advance Research, Diagnosis, and Treatment of Alcohol and Other Substance Use Disorders?

The current article highlights key issues in defining, studying, and treating addiction, a concept related to but distinct from substance use disorders. The discussion is based upon a roundtable discussion at the 2017 annual meeting of the Research Society on Alcoholism where Warren K. Bickel and John C. Crabbe were charged with answering a range of questions posed by Kenneth J. Sher. All the presenters highlighted a number of central concerns for those interested in assessing and treating addiction as well as those seeking to conduct basic preclinical research that is amenable to meaningful translation to the human condition. In addition, the discussion illustrated both the power and limitations of using any single theory to explain multiple phenomena subsumed under the rubric of addiction. Among the major issues examined were the important differences between traditional diagnostic approaches and current concepts of addiction, the difficulty of modeling key aspects of human addiction in nonhuman animals, key aspects of addiction that have, to date, received little empirical attention, and the importance of thinking of recovery as a phenomenon that possibly involves processes distinct from those undergirding the development and maintenance of addiction.

NOP-Related Mechanisms in Substance Use Disorders

Nociceptin/orphanin FQ (N/OFQ) is a 17 amino acid peptide that was deorphanized in 1995 and has been widely studied since. The role of the N/OFQ system in drug abuse has attracted researchers' attention since its initial discovery. The first two scientific papers describing the effect of intracranial injection of N/OFQ appeared 20 years ago and reported efficacy of the peptide in attenuating alcohol intake, whereas heroin self-administration was insensitive. Since then more than 100 scientific articles investigating the role of the N/OFQ and N/OFQ receptor (NOP) system in drug abuse have been published. The present article provides an historical overview of the advances in the field with focus on three major elements. First, the most robust data supportive of the efficacy of NOP agonists in treating drug abuse come from studies in the field of alcohol research, followed by psychostimulant and opioid research. In contrast, activation of NOP appears to facilitate nicotine consumption. Second, emerging data challenge the assumption that activation of NOP is the most appropriate strategy to attenuate consumption of substances of abuse. This assumption is based first on the observation that animals carrying an overexpression of NOP system components are more prone to consume substances of abuse, whereas NOP knockout rats are less motivated to self-administer heroin, alcohol, and cocaine. Third, administration of NOP antagonists also reduces alcohol consumption. In addition, NOP blockade reduces nicotine self-administration. Hypothetical mechanisms explaining this apparent paradox are discussed. Finally, we focus on the possibility that co-activation of NOP and mu opioid (MOP) receptors is an alternative strategy, readily testable in the clinic, to reduce the consumption of psychostimulants, opiates, and, possibly, alcohol.

Shaping vulnerability to addiction - the contribution of behavior, neural circuits and molecular mechanisms

Substance use disorders continue to impose increasing medical, financial and emotional burdens on society in the form of morbidity and overdose, family disintegration, loss of employment and crime, while advances in prevention and treatment options remain limited. Importantly, not all individuals exposed to abused substances effectively develop the disease. Genetic factors play a significant role in determining addiction vulnerability and interactions between innate predisposition, environmental factors and personal experiences are also critical. Thus, understanding individual differences that contribute to the initiation of substance use as well as on long-term maladaptations driving compulsive drug use and relapse propensity is of critical importance to reduce this devastating disorder. In this paper, we discuss current topics in the field of addiction regarding individual vulnerability related to behavioral endophenotypes, neural circuits, as well as genetics and epigenetic mechanisms. Expanded knowledge of these factors is of importance to improve and personalize prevention and treatment interventions in the future.

Initial subjective reward to alcohol in Sprague-Dawley rats

Initial subjective response to the rewarding properties of alcohol predicts voluntary consumption and the risk for alcohol use disorders. We assessed the initial subjective reward to alcohol in rats using a single exposure conditioned place preference (SE-CPP) paradigm. Sprague-Dawley rats demonstrate preference for a context paired with a single systemic injection of ethanol (1.0 g/kg, delivered intraperitoneally). However, expression of SE-CPP in males depended on pairing ethanol with the first exposure of two (ethanol; saline) to the conditioning apparatus and procedures, while conditioning day did not appreciably affect SE-CPP in females, consistent with the view that females experience heightened addiction vulnerability. This model offers researchers a high throughput assay for investigating factors that influence alcohol reward and may point the way toward more effective prevention and treatment efforts.

Neuropeptide S differently modulates alcohol-related behaviors in alcohol-preferring and non-preferring rats

RATIONALE

Neuropeptide S (NPS) displays unique pharmacological properties and induces both anxiolytic and pro-stress/arousal activities. Previous studies performed using Wistar rats demonstrated that NPS facilitated alcohol and cocaine seeking but did not affect alcohol or cocaine consumption.

OBJECTIVES

Here, we investigated the effects of NPS in Marchigian Sardinian alcohol-preferring (msP) rats, a rat strain characterized by excessive alcohol consumption comorbid with heightened anxiety and depressive-like phenotypes. Specifically, we evaluated the effect of NPS on operant alcohol self-administration by msP rats compared to Wistar rats. The effect of NPS on cue-induced reinstatement of alcohol seeking in msP rats was also evaluated. Finally, using the open field test (OFT) and the elevated plus maze (EPM), we evaluated the effects of NPS on locomotor activity and anxiety.

RESULTS

NPS reduced alcohol self-administration but did not affect cue-induced reinstatement in the msP rat. In addition, NPS induced reinstatement of extinguished alcohol seeking in Wistar rats without affecting alcohol intake. In the EPM task, NPS, in accordance with its anxiolytic activity, increased the time spent in the open arm of the arena by msP rats, although this effect was not observed in Wistar rats.

CONCLUSIONS

These data suggest that the effect of NPS is strongly influenced by the genetic background of the animal. In Wistar rats, NPS acts as a pro-arousal agent to promote the reinstatement of alcohol seeking. However, when alcohol drinking is motivated by or associated with a state of pathological anxiety, NPS attenuates alcohol consumption and seeking due to its anxiolytic activity.

Neurokinin 1 receptor blockade in the medial amygdala attenuates alcohol drinking in rats with innate anxiety but not in Wistar rats

BACKGROUND AND PURPOSE

Substance P and its preferred neurokinin receptor NK1 have been implicated in stress and anxiety and have been proposed as possible therapeutic targets for the treatment of anxiety/depression. Attention is also being focused on the role this neuropeptide system may play in drug addiction, because stress-related mechanisms promote drug abuse.

EXPERIMENTAL APPROACH

The effects of the rat-specific NK1 receptor antagonist, L822429, on alcohol intake and seeking behaviour was investigated in genetically selected Marchigian Sardinian alcohol preferring rats. These rats demonstrate an anxious phenotype and are highly sensitive to stress and stress-induced drinking.

KEY RESULTS

Systemic administration of L822429 significantly reduced operant alcohol self-administration in Marchigian Sardinian alcohol preferring rats, but did not reduce alcohol self-administration in stock Wistar rats. NK1 receptor antagonism also attenuated yohimbine-induced reinstatement of alcohol seeking at all doses tested but had no effect on cue-induced reinstatement of alcohol seeking. L822429 reduced operant alcohol self-administration when injected into the lateral cerebroventricles or the medial amygdala. L822429 injected into the medial amygdala also significantly reduced anxiety-like behaviour in the elevated plus maze test. No effects on alcohol intake were observed following injection of L822429 into the dorsal or the ventral hippocampus. Conclusions and Implications Our results suggest that NK1 receptor antagonists may be useful for the treatment of alcohol addiction associated with stress or comorbid anxiety disorders. The medial amygdala appears to be an important brain site of action of NK1 receptor antagonism.

Acetaldehyde sequestration by D-penicillamine prevents ethanol relapse-like drinking in rats: evidence from an operant self-administration paradigm

RATIONALE

Previous experiments in our laboratory have shown that D-penicillamine (DP) (acetaldehyde sequestering agent) is able to block the increase in ethanol consumption observed after a period of imposed deprivation (the so-called alcohol deprivation effect (ADE)), using a non-operant paradigm in Wistar rats.

OBJECTIVES

This study is aimed at investigating the robustness and reproducibility of our previous data using an operant paradigm, which is considered to be a valid and reliable model of human drug consumption, and the ADE, probably the most often used measure of ethanol relapse-drinking behaviour in rats.

METHODS

Male Wistar rats with a limited (30-min sessions), intermittent and extended background of ethanol operant self-administration were used. In order to evaluate the efficacy of several DP doses (6.25, 12.5 and 25 mg/kg i.p.) in preventing alcohol relapse, we set up a protocol based on the ADE. In a separate experiment, the effect of DP on spontaneous motor activity of rats was also tested.

RESULTS

A significant ADE was observed in animals treated with saline. DP treatment blocked the increase in ethanol responses following the imposed abstinence period. The higher dose suppressed the ADE and provoked a significant reduction in ethanol consumption with respect to the baseline conditions. Basal motor activity was not altered after DP treatment.

CONCLUSION

Our positive results with DP, using two different paradigms that evaluate relapse of ethanol drinking, will help to increase the positive predictive value of pre-clinical experiments and offer a solid base to inspire human studies with DP.

Sigma-1 receptor mediates acquisition of alcohol drinking and seeking behavior in alcohol-preferring rats

Sigma-1 receptor (Sig-1R) has been proposed as a novel therapeutic target for drug and alcohol addiction. We have shown previously that Sig-1R agonists facilitate the reinforcing effects of ethanol and induce binge-like drinking, while Sig-1R antagonists on the other hand block excessive drinking in genetic and environmental models of alcoholism, without affecting intake in outbred non-dependent rats. Even though significant progress has been made in understanding the function of Sig-1R in alcohol reinforcement, its role in the early and late stage of alcohol addiction remains unclear. Administration of the selective Sig-1R antagonist BD-1063 dramatically reduced the acquisition of alcohol drinking behavior as well as the preference for alcohol in genetically selected TSRI Sardinian alcohol preferring (Scr:sP) rats; the treatment had instead no effect on total fluid intake, food intake or body weight gain, proving selectivity of action. Furthermore, BD-1063 dose-dependently decreased alcohol-seeking behavior in rats trained under a second-order schedule of reinforcement, in which responding is maintained by contingent presentation of a conditioned reinforcer. Finally, an innate elevation in Sig-1R protein levels was found in the nucleus accumbens of alcohol-preferring Scr:sP rats, compared to outbred Wistar rats, alteration which was normalized by chronic, voluntary alcohol drinking. Taken together these findings demonstrate that Sig-1R blockade reduces the propensity to both acquire alcohol drinking and to seek alcohol, and point to the nucleus accumbens as a potential key region for the effects observed. Our data suggest that Sig-1R antagonists may have therapeutic potential in multiple stages of alcohol addiction.

Polymorphism in the corticotropin-releasing factor receptor 1 (CRF1-R) gene plays a role in shaping the high anxious phenotype of Marchigian Sardinian alcohol-preferring (msP) rats

INTRODUCTION

Marchigian Sardinian alcohol-preferring (msP) rats exhibit innate preference for alcohol along with anxious phenotype. In these animals, two single-nucleotide polymorphisms in position -1,836 and -2,097 from the first start codon of the CRF1-R transcript have been found.

MATERIALS AND METHODS

Here, we examined whether these point mutations account for the heightened anxiety-like behavior and stress responsiveness of msP rats. We rederived the msP rats to obtain two distinct lines carrying the wild-type (GG) and point mutations (AA), respectively.

RESULTS

CRF1-R gene expression analysis revealed significant dysregulation of the system in the extended amygdala of AA rats. At the behavioral level, using the elevated plus maze, we found that both AA and GG lines had higher basal anxiety compared to Wistar rats. In the defensive burying test, AA rats showed decreased burying behavior compared to the GG and the unselected Wistar lines. Freezing/immobility did not differ among AA and GG but was higher than that of Wistars. The selective CRF1-R antagonist antalarmin (0, 10, and 20 mg/kg) reduced burying behavior in Wistar animals. However, antalarmin (10 mg/kg) tended to increase rather than reducing this behavior when tested in the msP lines, an effect that appeared more marked in the GG as compared to the AA line.

CONCLUSION

The present data suggest that rats with msP genetic background are more anxious and show different sensitivity to stress and CRF1-R blockade than Wistars. The point mutations occurring in the CRF1-R gene do not seem to influence basal anxiety while they appear to affect active responses to stress.

Ethanol affects acylated and total ghrelin levels in peripheral blood of alcohol-dependent rats

There is a hypothesis that ghrelin could take part in the central effects of alcohol as well as function as a peripheral indicator of the changes which occur during long-term alcohol consumption. The aim of this study was to determine a correlation between alcohol concentration and acylated and total form of ghrelin after a single administration of alcohol (intraperitoneal, i.p.) (experiment 1) and prolonged ethanol consumption (experiment 2). The study was performed using Wistar alcohol preferring (PR) and non-preferring (NP) rats and rats from inbred line (Warsaw High Preferring, WHP; Warsaw Low Preferring, WLP). It was found that ghrelin in ethanol-naive WHP animals showed a significantly lower level when compared with the ethanol-naive WLP or Wistar rats. After acute ethanol administration in doses of 1.0; 2.0 and 4.0 g/kg, i.p., the simple (WHP) or inverse (WLP and Wistar) relationship between alcohol concentration and both form of ghrelin levels in plasma were found. Chronic alcohol intake in all groups of rats led to decrease of acylated ghrelin concentration. PR and WHP rats, after chronic alcohol drinking, had lower levels of both form of ghrelin in comparison with NP and WLP rats, respectively, and the observed differences in ghrelin levels were in inverse relationship with their alcohol intake. In conclusion, it is suggested that there is a strong relationship between alcohol administration or intake, ethanol concentration in blood and both active and total ghrelin level in the experimental animals, and that ghrelin plasma concentration can be a marker of alcohol drinking predisposition.

Role of a genetic polymorphism in the corticotropin-releasing factor receptor 1 gene in alcohol drinking and seeking behaviors of marchigian sardinian alcohol-preferring rats

Marchigian Sardinian alcohol-preferring (msP) rats exhibit innate preference for alcohol, are highly sensitive to stress and stress-induced alcohol seeking. Genetic analysis showed that over-expression of the corticotropin-releasing factor (CRF) system of msP rats is correlated with the presence of two single nucleotide polymorphisms (SNPs) occurring in the promoter region (position -1836 and -2097) of the CRF1 receptor (CRF1-R) gene. Here we examined whether these point mutations were associated to the innate alcohol preference, stress-induced drinking, and seeking. We have recently re-derived the msP rats to obtain two distinct lines carrying the wild type (GG) and the point mutations (AA), respectively. The phenotypic characteristics of these two lines were compared with those of unselected Wistar rats. Both AA and GG rats showed similar patterns of voluntary alcohol intake and preference. Similarly, the pharmacological stressor yohimbine (0.0, 0.625, 1.25, and 2.5 mg/kg) elicited increased operant alcohol self-administration under fixed and progressive ratio reinforcement schedules in all three lines. Following extinction, yohimbine (0.0, 0.625, 1.25, and 2.5 mg/kg) significantly reinstated alcohol seeking in the three groups. However, at the highest dose this effect was no longer evident in AA rats. Treatment with the CRF1-R antagonist antalarmin (0, 5, 10, and 20 mg/kg) significantly reduced alcohol-reinforced lever pressing in the AA line (10 and 20 mg/kg) while a weaker or no effect was observed in the Wistar and the GG group, respectively. Finally, antalarmin significantly reduced yohimbine-induced increase in alcohol drinking in all three groups. In conclusion, these specific SNPs in the CRF1-R gene do not seem to play a primary role in the expression of the msP excessive drinking phenotype or stress-induced drinking but may be associated with a decreased threshold for stress-induced alcohol seeking and an increased sensitivity to the effects of pharmacological blockade of CRF1-R on alcohol drinking.