Pharmacogenomics of alcohol response and addiction

Network States in the Basolateral Amygdala Predicts Voluntary Alcohol Consumption

Although most adults in the United States will drink alcohol in their life, only about 6% will go on to develop an alcohol use disorder (AUD). While a great deal of work has furthered our understanding of the cycle of addiction, it remains unclear why certain people transition to disordered drinking. Altered activity in regions implicated in AUDs, like the basolateral amygdala (BLA), has been suggested to play a role in the pathophysiology of AUDs, but how these networks contribute to alcohol misuse remains unclear. Our recent work demonstrated that alcohol can modulate BLA network states and that GABAergic parvalbumin (PV) interneurons are crucial modulators of network activity in the BLA. Further, our lab has demonstrated that δ subunit-containing GABA A receptors, which are modulated by alcohol, are highly expressed on PV interneurons in the BLA. These receptors on PV interneurons have also been shown to influence alcohol intake in a voluntary binge drinking paradigm and anxiety-like behavior in withdrawal. Therefore, we hypothesized that alcohol may impact BLA network states via δ subunit-containing GABA A receptors on PV interneurons to impact the extent of alcohol use. To test this hypothesis, we measured the impact of acute alcohol exposure on oscillatory states in the basolateral amygdala and then assessed the relationship to the extent of voluntary ethanol consumption in the Intermittent Access, Drinking-in-the-Dark-Multiple Scheduled Access, and Chronic Intermittent Ethanol exposure paradigms. Remarkably, we demonstrate that the average alcohol intake negatively correlates with δ subunit-containing GABA A receptor expression on PV interneurons and gamma power in the BLA after the first exposure to alcohol. These data implicate δ subunit-containing GABA A receptor expression on PV interneurons in the BLA in voluntary alcohol intake and suggest that BLA network states may serve as a useful biomarker for those at risk for alcohol misuse.

Significance Statement

Oscillatory states in the BLA have been demonstrated to drive behavioral states involved in emotional processing, including negative valence processing. Given that negative emotional states/hyperkatifeia contribute to the cycle of AUDs, our previous work demonstrating the ability of alcohol to modulate BLA network states and thereby behavioral states suggests that this mechanism may influence alcohol intake. Here we demonstrate a relationship between the ability of alcohol to modulate oscillations in the BLA and future alcohol intake such that the extent to which alcohol influences BLA network states predict the extent of future voluntary alcohol intake. These findings suggest that individual variability in the sensitivity of the BLA network to alcohol influences voluntary alcohol consumption.

Effect of chronic alcohol consumption on brain structure in males with alcohol use disorder without a familiar history of alcoholism

Structural brain damages caused by chronic alcohol consumption have been extensively reported. However, the neuroimaging findings in people with alcohol use disorder (AUD) are relatively inconsistent. This inconsistency may be due to the influence of different variables that are not always considered, such as the presence of a family history of alcoholism (FHA). The main aim of this research is to study the gray (GM) and white matter (WM) volumes in male participants with AUD without FHA compared to healthy control males (HC) without FHA. For this study, we included 19 participants with AUD without FHA and 18 HC males without FHA. T1-weighted images were acquired with a General Electric Signa Exite 1.5 T scanner. GM and WM tissues were calculated using Diffeomorphic Anatomical Registration Through Exponentiated Lie algebra (DARTEL). All analyses were controlled for age and total brain volume. The statistical threshold was calculated with AlphaSim and further adjusted to account for the non-isotropic smoothness of structural images, according to Hayasaka et al. (2004). The obtained main results showed that, relative to the HC group, the participants with AUD without FHA had significantly lower GM in several brain structures, reflecting relatively purely the effects of chronic alcohol intake on brain volume. GM structure integrity is relevant for the efficient functioning of low and high-order cognitive processes used in everyday life, and its damage seems to be related to the severity/intensity/chronicity of the AUD. As such, it becomes relevant to assess and follow brain structural changes through the dependence course.

Interventions to prevent periodontal disease in tobacco-, alcohol-, and drug-dependent individuals

Substance abuse affects more than one sixth of the world's population. More importantly, the nature of the abuse and the type of addictive substances available to individuals is increasing exponentially. All substances with abusive potential impact both the human immuno-inflammatory system and oral microbial communities, and therefore play a critical role in the etiopathogenesis of periodontal diseases. Evidence strongly supports the efficacy of professionally delivered cessation counseling. Dentists, dental therapists, and hygienists are ideally placed to deliver this therapy, and to spearhead efforts to provide behavioral and pharmacologic support for cessation. The purpose of this review is to examine the biologic mechanisms underlying their role in disease causation, to understand the pharmacologic and behavioral basis for their habituation, and to investigate the efficacy of population-based and personalized interventions in prevention of periodontal disease.

Probing the Manipulated Neurochemical Drive in Alcohol Addiction and Novel Therapeutic Advancements

Alcohol addiction is one of the highly prevalent neurological disorders and a major threat to public health in the 21st century. Alcohol addiction affects people from all age groups and often leads to other serious comorbidities. The pathophysiology of alcohol addiction involves imbalance between the excitatory and inhibitory neurotransmitters in the brain. These changes occur in various regions of the brain including reward circuit such as the ventral tegmental area (VTA), nucleus accumbens (NAc), and prefrontal cortex. In this review, we have discussed several neurochemical circuitries which get manipulated and maladapted during alcohol addiction. To date there is no effective therapeutic intervention in clinics devoid of side effects that can successfully treat the patients suffering from alcohol addiction. Understanding the neurobiological intricacies of alcohol addiction is critical for the development of novel anti-addiction therapeutics. Apart from this, we have also discussed the recent therapeutic milestones for the management of alcohol addiction including vasopressin receptors, corticotrophin-releasing factor, GABA receptors, glucocorticoid receptors, brain stimulation and mindfulness-oriented recovery enhancement.

Sintomas de Depressão, Ansiedade e Estresse em Usuários de Drogas em Tratamento em Comunidades Terapêuticas

Resumo Sintomas de depressão, ansiedade e estresse podem interferir negativamente no progresso do tratamento de usuários de substâncias. Este estudo objetivou avaliar os níveis de depressão, ansiedade e estresse em homens e mulheres em tratamento em Comunidades Terapêuticas, relacionando tais níveis com o tipo de substância utilizada e dados sociodemográficos. Utilizou-se um Questionário de Dados Sociodemográficos e de Uso de Drogas e a escala DASS-21. Participaram 115 homens e 53 mulheres, em tratamento, totalizando 168 indivíduos, com idade média de 32 anos (DP = 8,7). A maioria eram usuários de tabaco e crack, este último associado às mulheres. Identificou-se que os usuários de tabaco e os usuários de drogas que não tinham emprego se associaram a níveis mais altos dos sintomas de depressão, ansiedade e estresse. Conclui-se que tais estratégias podem auxiliar na diminuição dos sintomas avaliados pelo DASS-21, melhorando as condições de vida para o enfrentamento do transtorno por uso de substâncias.

Sex differences in incentive motivation and the relationship to the development and maintenance of alcohol use disorders

Despite considerable evidence of higher rates of alcohol use disorders (AUDs) in men than in women, there is a dearth of research into the underlying causes of this disparity. As the gap in high risk drinking between men and women closes, it is critical to disentangle the biological factors that may place men and women at different risk for the development of AUDs as well as AUD-associated health problems. While sex differences in alcohol drinking have been reported in animal models and in human alcoholics, it increasingly seems that consummatory behavior may be dissociated from propensity toward inflexible and cue-elicited drug seeking and taking that characterize alcohol use disorders. While much of this work was initially performed in males a growing, yet limited, body of literature suggests that there are sex differences in both cue reactivity, and further, the relationship between cue reactivity and the maintenance of addictive behavior, indicating that males may be at greater risk for the development of a subset of addiction-related behaviors independent of alcohol consumption. Here, we will review the current literature on sex effects on the relationship between incentive motivation and addictive behavior and discuss unanswered questions that we expect will inform the development of individualized and sex-specific treatment and prevention strategies for AUDs. We believe that a greater understanding of how sex interacts with in cue reactivity to independently mediate the drug taking and risk for the development of uncontrolled drug or alcohol-seeking and -taking will inform the development of individualized treatment and prevention strategies for addiction.

A preclinical model for identifying rats at risk of alcohol use disorder

Alcohol use is one of the world's leading causes of death and disease, although only a small proportion of individuals develop persistent alcohol use disorder (AUD). The identification of vulnerable individuals prior to their chronic intoxication remains of highest importance. We propose here to adapt current methodologies for identifying rats at risk of losing control over alcohol intake by modeling diagnostic criteria for AUD: inability to abstain during a signaled period of reward unavailability, increased motivation assessed in a progressive effortful task and persistent alcohol intake despite aversive foot shocks. Factor analysis showed that these three addiction criteria loaded on one underlying construct indicating that they represent a latent construct of addiction trait. Further, not only vulnerable rats displayed higher ethanol consumption, and higher preference for ethanol over sweetened solutions, but they also exhibited pre-existing higher anxiety as compared to resilient rats. In conclusion, the present preclinical model confirms that development of an addiction trait not only requires prolonged exposure to alcohol, but also depends on endophenotype like anxiety that predispose a minority of individuals to lose control over alcohol consumption.

Review: Pharmacogenetics of alcoholism treatment: Implications of ethnic diversity

BACKGROUND AND OBJECTIVES

Pharmacogenetic studies of alcohol use disorder (AUD) have suggested that the efficacy of treatments for AUD is, in part, influenced by the genetic background of an individual. Since the frequency of alleles associated with pharmacotherapy for AUD varies by ancestral background, the effectiveness of medications used to treat AUD may vary among different populations. The purpose of this review is to summarize the existing pharmacogenetic studies of treatments for AUD in individuals of European, East Asian, African, and American Indian/Alaska Native ancestry.

METHODS

Electronic databases were searched for pharmacogenetic studies of AUD treatment that included individuals of diverse ancestral backgrounds.

RESULTS

Pharmacogenetic studies of AUD reviewed here have primarily investigated genetic variation thought to play a role in the response to naltrexone, ondansetron, and topiramate. There is support that the A118G polymorphism should be further investigated in individuals of East Asian ancestry.

DISCUSSION AND CONCLUSIONS

Given the lack of pharmacogenetic research on response to AUD medication in ethnic minority populations and the mixed results, there is a critical need for future studies among individuals of different ancestries. More efforts should be devoted to standardizing procedures such that results can be more readily integrated into a body of literature that can directly inform clinical practice.

SCIENTIFIC SIGNIFICANCE

This review highlights the importance for future research to aim for inclusiveness in pharmacogenetic studies of AUD and increase diversity of clinical trials in order to provide the best treatment outcomes for individuals across different racial and ethnic groups. (Am J Addict 2017;26:516-525).

Emergence of sex differences in the development of substance use and abuse during adolescence

Substance use and abuse begin during adolescence. Male and female adolescent humans initiate use at comparable rates, but males increase use faster. In adulthood, more men than women use and abuse addictive drugs. However, some women progress more rapidly from initiation of use to entry into treatment. In animal models, adolescent males and females consume addictive drugs similarly. However, reproductively mature females acquire self-administration faster, and in some models, escalate use more. Sex/gender differences exist in neurobiologic factors mediating both reinforcement (dopamine, opioids) and aversiveness (CRF, dynorphin), as well as intrinsic factors (personality, psychiatric co-morbidities) and extrinsic factors (history of abuse, environment especially peers and family) which influence the progression from initial use to abuse. Many of these important differences emerge during adolescence, and are moderated by sexual differentiation of the brain. Estradiol effects which enhance both dopaminergic and CRF-mediated processes contribute to the female vulnerability to substance use and abuse. Testosterone enhances impulsivity and sensation seeking in both males and females. Several protective factors in females also influence initiation and progression of substance use including hormonal changes of pregnancy as well as greater capacity for self-regulation and lower peak levels of impulsivity/sensation seeking. Same sex peers represent a risk factor more for males than females during adolescence, while romantic partners increase risk for women during this developmental epoch. In summary, biologic factors, psychiatric co-morbidities as well as personality and environment present sex/gender-specific risks as adolescents begin to initiate substance use.

cStress: Towards a Gold Standard for Continuous Stress Assessment in the Mobile Environment

Recent advances in mobile health have produced several new models for inferring stress from wearable sensors. But, the lack of a gold standard is a major hurdle in making clinical use of continuous stress measurements derived from wearable sensors. In this paper, we present a stress model (called cStress) that has been carefully developed with attention to every step of computational modeling including data collection, screening, cleaning, filtering, feature computation, normalization, and model training. More importantly, cStress was trained using data collected from a rigorous lab study with 21 participants and validated on two independently collected data sets - in a lab study on 26 participants and in a week-long field study with 20 participants. In testing, the model obtains a recall of 89% and a false positive rate of 5% on lab data. On field data, the model is able to predict each instantaneous self-report with an accuracy of 72%.

Pharmacological management of alcohol dependence: from mono-therapy to pharmacogenetics and beyond

Almost 10% of the world's population is affected by alcohol use disorders, and the treatment of alcohol dependence (AD) still remains a challenge. Patients with AD can differ in many traits. Three drugs (disulfiram, naltrexone, and acamprosate) have been approved by the FDA for the treatment of AD, and in some European countries sodium oxybate is also approved for this purpose. Combined pharmacological therapy has not provided such convincing results. Considering the fact that the "ideal" and effective drug for all types of alcoholic patients does not exists, the future challenge will be to identify a personalized approach. Recent data has shown that this objective can be achieved by investigating the genetic variability of the patient. Moreover, the use of replacement molecules can probably be considered an advantageous therapeutic opportunity (i.e. sodium oxybate). In addition, reduction of alcohol consumption is increasingly accepted as a viable treatment goal, and the use of nalmefene "as-needed" (a pharmacological approach similar to naltrexone, but, possibly, with lower hepatotoxicity) may help in the treatment of AD. Thus, it is important to stress that a pharmacological approach to treat AD should be preceded by the definition of patient characteristics; this may help in the choice of the most appropriate drug and it can be done more easily when more pharmacological options approved for the treatment of AD are also available.

Are We There Yet? Feasibility of Continuous Stress Assessment via Wireless Physiological Sensors

Stress can lead to headaches and fatigue, precipitate addictive behaviors (e.g., smoking, alcohol and drug use), and lead to cardiovascular diseases and cancer. Continuous assessment of stress from sensors can be used for timely delivery of a variety of interventions to reduce or avoid stress. We investigate the feasibility of continuous stress measurement via two field studies using wireless physiological sensors - a four-week study with illicit drug users (n = 40), and a one-week study with daily smokers and social drinkers (n = 30). We find that 11+ hours/day of usable data can be obtained in a 4-week study. Significant learning effect is observed after the first week and data yield is seen to be increasing over time even in the fourth week. We propose a framework to analyze sensor data yield and find that losses in wireless channel is negligible; the main hurdle in further improving data yield is the attachment constraint. We show the feasibility of measuring stress minutes preceding events of interest and observe the sensor-derived stress to be rising prior to self-reported stress and smoking events.

Genetically selected alcohol preferring rats to model human alcoholism

Animal models have been successfully developed to mimic and study alcoholism. These models have the unique feature of allowing the researcher to control for the genetic characteristics of the animal, alcohol exposure and environment. Moreover, these animal models allow pharmacological, neurochemical and behavioral manipulations otherwise impossible. Unquestionably, one of the major contributions to the understanding of the neurobiological basis of alcoholism comes from data that have been obtained from the study of genetically selected alcohol preferring rat lines and from the consequences that alcohol drinking and environmental manipulations, (i.e., protracted alcohol drinking, intoxication, exposure to stress, etc.) have on them. In fact, if on the one hand genetic factors may account for about 50-60% of the risk of developing alcohol dependence, on the other hand protracted alcohol exposure is a necessary precondition to actually develop the disease, while environmental vulnerability factors may be crucial for disease progression. The present article will offer an overview of the different genetically selected alcohol preferring rat lines developed and used to study alcoholism. The predictive, face and construct validity of these animal models and the translational significance of findings achieved through their use will be critically discussed.

Selection for high alcohol preference drinking in mice results in heightened sensitivity and rapid development of acute functional tolerance to alcohol's ataxic effects

Propensity to develop acute functional (or within session) tolerance to alcohol (ethanol) may influence the amount of alcohol consumed, with higher drinking associated with greater acute functional tolerance (AFT). The goal of this study was to assess this potential correlated response between alcohol preference and AFT in second and third replicate lines of mice selectively bred for high (HAP2 and HAP3) and low (LAP2 and LAP3) alcohol preference drinking. Male and female mice were tested for development of AFT on a static dowel task, which requires that animals maintain balance on a wooden dowel in order to prevent falling. On test day, each mouse received one (1.75 g/kg; Experiment 1) or two (1.75 and 2.0 g/kg; Experiment 2) injections of ethanol; an initial administration before being placed on the dowel and in Experiment 2, an additional administration after the first regain of balance on the dowel. Blood samples were taken immediately after loss of balance [when blood ethanol concentrations (BECs) were rising] and at recovery (during falling BECs) in Experiment 1, and after first and second recovery in Experiment 2. It was found that HAP mice fell from the dowel significantly earlier and at lower BECs than LAP mice following the initial injection of ethanol and were therefore more sensitive to its early effects. Furthermore, Experiment 1 detected significantly greater AFT development (BECfalling--BECrising) in HAP mice when compared with LAP mice, which occurred within ~30 min, supporting our hypothesis. However, AFT was not different between lines in Experiment 2, indicating that ~30-60 min following alcohol administration, AFT development was similar in both lines. These data show that high alcohol drinking genetically associates with both high initial sensitivity and very early tolerance to the ataxic effects of ethanol.

The role of amygdaloid brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein and dendritic spines in anxiety and alcoholism

Innate anxiety appears to be a robust factor in the promotion of alcohol intake, possibly due to the anxiolytic effects of self-medication with alcohol. Brain-derived neurotrophic factor (BDNF) and its downstream target, activity-regulated cytoskeleton-associated (Arc) protein, play a role in the regulation of synaptic function and structure. In order to examine the role of the BDNF-Arc system and associated dendritic spines in the anxiolytic effects of ethanol, we investigated the effects of acute ethanol exposure on anxiety-like behaviors of alcohol-preferring (P) and -nonpreferring (NP) rats. We also examined changes in the expression of BDNF and Arc, and dendritic spine density (DSD), in amygdaloid brain regions of P and NP rats with or without ethanol exposure. It was found that in comparison with NP rats, P rats displayed innate anxiety-like behaviors, and had lower mRNA and protein levels of both BDNF and Arc, and also had lower DSD in the central amygdala (CeA) and medial amygdala (MeA), but not in the basolateral amygdala (BLA). Acute ethanol treatment had an anxiolytic effect in P, but not in NP rats, and was associated with an increase in mRNA and protein levels of BDNF and Arc, and in DSD in the CeA and MeA, but not BLA. These results suggest that innate deficits in BDNF-Arc levels, and DSD, in the CeA and MeA may be involved in the anxiety-like and excessive alcohol-drinking behaviors of P rats, as ethanol increased these amygdaloid synaptic markers and produced anxiolytic effects in P rats, but not NP rats.

Genome-wide association studies of alcohol dependence and substance use disorders

Genome-wide association studies (GWAS) currently represent the most systematic approach to genetic research into complex disorders. They can detect associations of common variants in genomic regions in the absence of an a priori assumption. Most of the GWAS of addiction performed to date have focused on alcohol dependence or smoking behavior. Four GWAS of alcohol dependence have been published thus far, and only two single nucleotide polymorphisms have received modest support of replication in a subsequent study. Many more GWAS have been conducted for smoking behavior. One large, single GWAS and meta-analyses of the phenotype "smoking quantity" have generated convincing evidence for the contribution of variants in genes for cholinergic nicotinic receptor subunits. This article focuses on GWAS of alcohol addiction and provides an overview of GWAS of other substance abuse disorders.

Violência, dependência química e transtornos mentais em presidiários

O presente trabalho realizou uma análise de artigos científicos selecionados nas fontes eletrônicas SciELO, PubMed e Web of Science, no período entre 1998 e 2008. Na elaboração da revisão e na discussão de dados, foram utilizados os descritores: violência (violence); dependência de drogas (drug dependence), transtornos mentais (mental disturbs) e prisioneiros (prisoners). No total, foram encontrados 408 artigos sobre a temática, tendo sido utilizados 60 deles, juntamente com 23 livros e teses que abordam a problemática em questão. A revisão teve por objetivo analisar a relação entre violência, dependência química e transtornos mentais na população carcerária masculina. Os resultados mostraram que o uso abusivo de drogas é um importante fator de risco para a violência e que os transtornos mentais, muitas vezes, acompanham atos violentos. Conclui-se que a violência e a dependência de drogas estão diretamente relacionadas em prisioneiros.

Chronic cigarette smoking: implications for neurocognition and brain neurobiology

Compared to the substantial volume of research on the general health consequences associated with chronic smoking, little research has been specifically devoted to the investigation of its effects on human neurobiology and neurocognition. This review summarizes the peer-reviewed literature on the neurocognitive and neurobiological implications of chronic cigarette smoking in cohorts that were not seeking treatment for substance use or psychiatric disorders. Studies that specifically assessed the neurocognitive or neurobiological (with emphasis on computed tomography and magnetic resonance-based neuroimaging studies) consequences of chronic smoking are highlighted. Chronic cigarette smoking appears to be associated with deficiencies in executive functions, cognitive flexibility, general intellectual abilities, learning and/or memory processing speed, and working memory. Chronic smoking is related to global brain atrophy and to structural and biochemical abnormalities in anterior frontal regions, subcortical nuclei and commissural white matter. Chronic smoking may also be associated with an increased risk for various forms of neurodegenerative diseases. The existing literature is limited by inconsistent accounting for potentially confounding biomedical and psychiatric conditions, focus on cross-sectional studies with middle aged and older adults and the absence of studies concurrently assessing neurocognitive, neurobiological and genetic factors in the same cohort. Consequently, the mechanisms promoting the neurocognitive and neurobiological abnormalities reported in chronic smokers are unclear. Longitudinal studies are needed to determine if the smoking-related neurobiological and neurocognitive abnormalities increase over time and/or show recovery with sustained smoking cessation.

OPRM1 SNP (A118G): involvement in disease development, treatment response, and animal models

Endogenous opioids acting at mu-opioid receptors mediate many biological functions. Pharmacological intervention at these receptors has greatly aided in the treatment of acute and chronic pain, in addition to other uses. However, the development of tolerance and dependence has made it difficult to adequately prescribe these therapeutics. A common single nucleotide polymorphism (SNP), A118G, in the mu-opioid receptor gene can affect opioid function and, consequently, has been suggested to contribute to individual variability in pain management and drug addiction. Investigation into the role of A118G in human disease and treatment response has generated a large number of association studies across various disease states as well as physiological responses. However, characterizing the functional consequences of this SNP and establishing if it causes or contributes to disease phenotypes have been significant challenges. In this manuscript, we will review a number of association studies as well as investigations of the functional impact of this gene variant. In addition, we will describe a novel mouse model that was generated to recapitulate this SNP in mice. Evaluation of models that incorporate known human genetic variants into a tractable system, like the mouse, will facilitate the understanding of discrete contributions of SNPs to human disease.

Neuropeptide Y signaling in the central nucleus of amygdala regulates alcohol-drinking and anxiety-like behaviors of alcohol-preferring rats

BACKGROUND

The neuropeptide Y (NPY) system of the central nucleus of amygdala (CeA) has been shown to be involved in anxiety and alcoholism. In this study, we investigated the molecular mechanisms by which NPY in the CeA regulates anxiety and alcohol drinking behaviors using alcohol-preferring (P) rats as an animal model.

METHODS

Alcohol-preferring rats were bilaterally cannulated targeting the CeA and infused with artificial cerebrospinal fluid (aCSF) or NPY. Alcohol drinking and anxiety-like behaviors were assessed by the 2-bottle free-choice paradigm and light/dark box (LDB) exploration test, respectively. The levels of NPY and related signaling proteins were determined by the gold immunolabeling procedure. The mRNA levels of NPY were measured by in situ RT-PCR. Double-immunofluorescence labeling was performed to observe the colocalization of NPY and Ca(2+)/calmodulin-dependent protein kinase IV (CaMK IV).

RESULTS

We found that NPY infusion into the CeA produced anxiolytic effects, as measured by the LDB exploration test, and also decreased alcohol intake in P rats. NPY infusion into the CeA significantly increased levels of CaMK IV and phosphorylated cAMP responsive element-binding (pCREB) protein and increased mRNA and protein levels of NPY, but produced no changes in protein levels of CREB or the catalytic alpha-subunit of protein kinase A (PKA-Calpha) in the CeA. We also observed that alcohol intake produced anxiolytic effects in P rats in the LDB test and also increased NPY expression and protein levels of pCREB and PKA-Calpha without modulating protein levels of CREB or CaMK IV, in both the CeA and medial nucleus of amygdala. In addition, we found that CaMK IV-positive cells were co-localized with NPY in amygdaloid structures of P rats.

CONCLUSIONS

These results suggest that NPY infusion may increase the expression of endogenous NPY in the CeA, which is most likely attributable to an increase in CaMK IV-dependent CREB phosphorylation and this molecular mechanism may be involved in regulating anxiety and alcohol drinking behaviors of P rats.

Sex differences in NMDA receptor expression in human alcoholics

AIM

The aim of this study was to assess whether chronic alcohol misuse affects N-methyl-d-aspartate (NMDA) receptor subunit concentrations in human cases, and whether male and female subjects respond differently.

METHODS

Real-time RT-PCR normalized to GAPDH was used to assay NR1, NR2A and NR2B subunit mRNA in superior frontal (SFC) and primary motor (PMC) cortex tissue obtained at autopsy from chronic alcoholics with and without comorbid cirrhosis of the liver, and from matched controls.

RESULTS

The expression of all three subunits was significantly lower in both areas of cirrhotic alcoholics than in either controls or alcoholics without comorbid disease, who did not differ significantly. Values were also influenced by the subject's sex and genotype. The mu-opiate receptor C1031G polymorphism selectively modulated NMDA transcript expression in cirrhotic-alcoholic SFC, an effect that was more marked for NR1 and NR2A than for NR2B subunit transcripts. Contrasting 5HT1B genotypes affected NMDA mRNA expression differently in male and female SFC, but not PMC, in cirrhotic alcoholics.

CONCLUSION

NMDA receptor subunit expression may differentially influence male and female cirrhotic alcoholics' susceptibility to brain damage.

Genome-wide association study of alcohol dependence

CONTEXT

Alcohol dependence is a serious and common public health problem. It is well established that genetic factors play a major role in the development of this disorder. Identification of genes that contribute to alcohol dependence will improve our understanding of the mechanisms that underlie this disorder.

OBJECTIVE

To identify susceptibility genes for alcohol dependence through a genome-wide association study (GWAS) and a follow-up study in a population of German male inpatients with an early age at onset.

DESIGN

The GWAS tested 524,396 single-nucleotide polymorphisms (SNPs). All SNPs with P < 10(-4) were subjected to the follow-up study. In addition, nominally significant SNPs from genes that had also shown expression changes in rat brains after long-term alcohol consumption were selected for the follow-up step.

SETTING

Five university hospitals in southern and central Germany.

PARTICIPANTS

The GWAS included 487 male inpatients with alcohol dependence as defined by the DSM-IV and an age at onset younger than 28 years and 1358 population-based control individuals. The follow-up study included 1024 male inpatients and 996 age-matched male controls. All the participants were of German descent.

MAIN OUTCOME MEASURES

Significant association findings in the GWAS and follow-up study with the same alleles.

RESULTS

The GWAS produced 121 SNPs with nominal P < 10(-4). These, together with 19 additional SNPs from homologues of rat genes showing differential expression, were genotyped in the follow-up sample. Fifteen SNPs showed significant association with the same allele as in the GWAS. In the combined analysis, 2 closely linked intergenic SNPs met genome-wide significance (rs7590720, P = 9.72 x 10(-9); rs1344694, P = 1.69 x 10(-8)). They are located on chromosome region 2q35, which has been implicated in linkage studies for alcohol phenotypes. Nine SNPs were located in genes, including the CDH13 and ADH1C genes, that have been reported to be associated with alcohol dependence.

CONCLUSIONS

This is the first GWAS and follow-up study to identify a genome-wide significant association in alcohol dependence. Further independent studies are required to confirm these findings.

Assessing appetitive, aversive, and negative ethanol-mediated reinforcement through an immature rat model

The motivational effects of drugs play a key role during the transition from casual use to abuse and dependence. Ethanol reinforcement has been successfully studied through Pavlovian and operant conditioning in adult rats and mice genetically selected for their ready acceptance of ethanol. Another model for studying ethanol reinforcement is the immature (preweanling) rat, which consumes ethanol and exhibits the capacity to process tactile, odor and taste cues and transfer information between different sensorial modalities. This review describes the motivational effects of ethanol in preweanling, heterogeneous non-selected rats. Preweanlings exhibit ethanol-mediated conditioned taste avoidance and conditioned place aversion. Ethanol's appetitive effects, however, are evident when using first- and second-order conditioning and operant procedures. Ethanol also devalues the motivational representation of aversive stimuli, suggesting early negative reinforcement. It seems that preweanlings are highly sensitive not only to the aversive motivational effects of ethanol but also to its positive and negative (anti-anxiety) reinforcement potential. The review underscores the advantages of using a developing rat to evaluate alcohol's motivational effects.

Morphine attenuates the expression of sensitization to ethanol, but opioid antagonists do not

Behavioral sensitization to ethanol is characterized by an increased locomotor activity after repeated exposure. A great variability exists among species and strains in the development of sensitization. There is a growing amount of evidence to indicate that the opioid system is involved in alcoholism; it is possible, therefore, that this system also modulates the sensitization to ethanol. In this study we evaluated the role of the opioid system in determining the variability of the sensitized response to ethanol. Mice received repeated administrations of ethanol (2.2 g/kg) or saline every other day for 10 days. According to their locomotor response on the last day of treatment, ethanol-treated animals were classified into two groups: sensitized or non-sensitized mice. After the treatment, mice were submitted to four challenges 48 h apart. In experiments 1 and 2, mice were challenged, respectively, with i.p. administration of opioid antagonists (naloxone or naltrexone) or an opioid agonist (morphine), followed immediately by 2.2 g/kg ethanol. In experiment 3, animals received morphine by i.c.v., followed by 2.2 g/kg of ethanol (i.p.). Pretreatment with opioid antagonists (naloxone or naltrexone) did not block the expression of ethanol sensitization; however pretreatment with morphine attenuated the increased locomotor activity after ethanol administration in sensitized mice. In experiment 4, after the ethanol or saline treatment, mice brains were processed and brain mu opioid binding was assessed by autoradiography using [3H]D-Ala2,N-mePhe4, Gly-ol5-enkephalin ([3H]DAMGO). No differences were seen between any of the groups of mice, so the agonist effect is not likely to be mediated by differences in binding to mu opioid receptors.

The relationship of 5HTT (SLC6A4) methylation and genotype on mRNA expression and liability to major depression and alcohol dependence in subjects from the Iowa Adoption Studies

Serotonin Transporter (5HTT or SLC6A4) mRNA transcription is regulated by both genetic and epigenetic mechanisms. Unfortunately, despite intense scrutiny, the exact identity and contribution of each of these regulatory mechanisms, and their relationship to behavioral illness remain unknown. This lack of knowledge is critical because alterations in SLC6A4 function are posited to be central to a wide variety of CNS disorders. In order to address this shortcoming, we quantified 5HTTLPR genotype, SLC6A4 mRNA production and CpG methylation using biomaterial from 192 lymphoblast cell lines derived from subjects who participated in the latest wave of the Iowa Adoption Studies. We then analyzed the resulting data with respect to clinical characteristics. We confirmed prior findings that the short (s) 5HTTLPR allele is associated with lower amounts of mRNA transcription, but there was no significant effect of the "Long G" allele on mRNA transcription. We also found that CpG methylation was higher (P < 0.0008) and mRNA production (P < 0.0001) was lower in females as compared to males. Those subjects with a lifetime history of Alcohol Dependence had higher levels of SLC6A4 mRNA. There was a trend for an association of increased overall methylation with lifetime history of major depression. Finally, we confirm our prior findings that the exact levels of 5HTT mRNA expression are dependent on how it is measured. We conclude that both genetic variation and epigenetic modifications contribute to the regulation of SLC6A4 function and that more in-depth studies of the molecular mechanisms controlling gene activity and the relationship of these mechanisms to behavioral illness are indicated.

Innate differences in the expression of brain-derived neurotrophic factor in the regions within the extended amygdala between alcohol preferring and nonpreferring rats

BACKGROUND

Animal lines such as alcohol-preferring (P) and nonpreferring (NP) rats appear to be suitable animal models to investigate the biological basis of alcohol-drinking behaviors. The extended amygdala serves as a neuroanatomical substrate for alcohol-drinking behaviors. Brain-derived neurotrophic factor (BDNF) in the amygdala has been implicated in alcohol-drinking behaviors; however, its expression in the extended amygdala of P and NP rats is unknown. Therefore, we examined the basal expression of BDNF in the extended amygdala of alcohol naive P and NP rats.

METHODS

We determined the basal mRNA and protein levels of BDNF by in situ RT-PCR and immuno-histochemical procedure, respectively, in the amygdaloid [central nucleus of amygdala (CeA), medial nucleus of amygdala (MeA), and basolateral amygdala (BLA)], nucleus accumbal (NAc shell and core), and bed nucleus of stria terminalis (BNST) [lateral BNST (lBNST), medial BNST (mBNST), and ventral BNST (vBNST)] brain structures of P and NP rats. In addition, we examined the localization of BDNF in neurons using double-immunofluorescence labeling of BDNF with neuron-specific nuclear protein (NeuN) and also determined the number of NeuN-positive neurons in the amygdaloid structures of P and NP rats.

RESULTS

The mRNA and protein levels of BDNF were found to be significantly lower in both the CeA and MeA, but not in the BLA, of P compared with NP rats. We also found that BDNF was expressed in neurons in the amygdaloid structures of P and NP rats. In addition, we found that the number of NeuN-positive neurons was similar in the amygdaloid structures of P and NP rats. Interestingly, the mRNA and protein levels of BDNF were also significantly lower in the lBNST, mBNST, and vBNST of P compared with NP rats. On the other hand, mRNA and protein levels of BDNF were similar in the NAc shell and core structures of P and NP rats.

CONCLUSIONS

P and NP rats are selectively bred for higher and lower alcohol preference, respectively; therefore it is possible that lower BDNF levels in the amygdaloid and BNST structures may be associated with the excessive alcohol-drinking behaviors of P rats.

Modulation of voluntary ethanol consumption by beta-arrestin 2

Beta-arrestin 2 is a multifunctional key component of the G protein-coupled receptor complex and is involved in mu-opiate and dopamine D2 receptor signaling, both of which are thought to mediate the rewarding effects of ethanol consumption. We identified elevated expression of the beta-arrestin 2 gene (Arrb2) in the striatum and the hippocampus of ethanol-preferring AA rats compared to their nonpreferring counterpart ANA line. Differential mRNA expression was accompanied by different levels of Arrb2 protein. The elevated expression was associated with a 7-marker haplotype in complete linkage disequilibrium, which segregated fully between the lines, and was unique to the preferring line. Furthermore, a single, distinct, and highly significant quantitative trait locus for Arrb2 expression in hippocampus and striatum was identified at the locus of this gene, providing evidence that genetic variation may affect a cis-regulatory mechanism for expression and regional control of Arrb2. These findings were functionally validated using mice lacking Arrb2, which displayed both reduced voluntary ethanol consumption and ethanol-induced psychomotor stimulation. Our results demonstrate that beta-arrestin 2 modulates acute responses to ethanol and is an important mediator of ethanol reward.

The role of GABA(A) receptors in the development of alcoholism

Alcoholism is a common, heritable, chronic relapsing disorder. GABA(A) receptors undergo allosteric modulation by ethanol, anesthetics, benzodiazepines and neurosteroids and have been implicated in the acute as well as the chronic effects of ethanol including tolerance, dependence and withdrawal. Medications targeting GABA(A) receptors ameliorate the symptoms of acute withdrawal. Ethanol induces plasticity in GABA(A) receptors: tolerance is associated with generally decreased GABA(A) receptor activation and differentially altered subunit expression. The dopamine (DA) mesolimbic reward pathway originating in the ventral tegmental area (VTA), and interacting stress circuitry play an important role in the development of addiction. VTA GABAergic interneurons are the primary inhibitory regulators of DA neurons and a subset of VTA GABA(A) receptors may be implicated in the switch from heavy drinking to dependence. GABA(A) receptors modulate anxiety and response to stress; important elements of sustained drinking and relapse. The GABA(A) receptor subunit genes clustered on chromosome 4 are highly expressed in the reward pathway. Several recent studies have provided strong evidence that one of these genes, GABRA2, is implicated in alcoholism in humans. The influence of the interaction between ethanol and GABA(A) receptors in the reward pathway on the development of alcoholism together with genetic and epigenetic vulnerabilities will be explored in this review.

Strain differences in alcohol-induced neurochemical plasticity: a role for accumbens glutamate in alcohol intake

BACKGROUND

Repeated alcohol administration alters nucleus accumbens (NAC) basal glutamate content and sensitizes the capacity of alcohol to increase NAC extracellular glutamate levels. However, the relevance of alcohol-induced changes in NAC glutamate for alcohol drinking behavior is under-investigated.

METHODS

To examine the relationship between genetic variance in alcohol consumption and alcohol-induced neuroadaptations within the NAC, in vivo microdialysis was conducted in the alcohol-preferring C57BL/6J (B6) and alcohol-avoiding DBA2/J (D2) mouse strains on injections 1 and 8 of repeated alcohol treatment (8 x 2 g/kg, IP). To confirm an active role for NAC glutamate in regulating alcohol drinking behavior, the glutamate reuptake inhibitor dl-threo-beta-benzyloxyaspartic acid (TBOA) (300 microM) and the Group 2 metabotropic glutamate autoreceptor agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (APDC) (50 microM) were infused into the NAC of B6 and D2 mice prior to alcohol consumption in a 4 bottle-choice test.

RESULTS

While strain differences were not apparent for NAC basal levels of dopamine, serotonin or gamma-amino butyric acid (GABA), repeated alcohol treatment elevated NAC basal glutamate content only in B6 mice. Strain differences in both the acute and the sensitized neurochemical responses to 2 g/kg alcohol were observed for all neurotransmitters examined. While the alcohol-induced rise in NAC dopamine and glutamate levels sensitized in B6 mice, a sensitization was not observed in D2 animals. Moreover, B6 mice exhibited a sensitized serotonin and GABA response to alcohol followed repeated treatment, whereas neither tolerance nor sensitization was observed in D2 animals. An intra-NAC APDC infusion reduced alcohol intake in both B6 and D2 mice by approximately 50%. In contrast, TBOA infusion elevated alcohol intake selectively in B6 mice.

CONCLUSIONS

These data indicate an active role for NAC glutamate in regulating alcohol consumption in mice and support the hypothesis that predisposition to high alcohol intake involves genetic factors that facilitate alcohol-induced adaptations in glutamate release within the NAC.

Anticipating clinical integration of pharmacogenetic treatment strategies for addiction: are primary care physicians ready?

Emerging pharmacogenomics research on addiction to nicotine, alcohol, cocaine, and opiates may soon lead to improved clinical outcomes by tailoring the type, dose and duration of treatment to individual patients' genotypes. To realize the potential of pharmacogenomics in reducing the burden of addiction, several challenges related to clinical integration of novel treatment strategies will need to be addressed concomitantly with ongoing empirical research. These challenges include the preparedness of primary care physicians (PCPs) to incorporate pharmacogenetics into clinical practice, patients' willingness to undergo genetic testing, the resources and infrastructure needed to deliver such services, adequate financing and reimbursement of pharmacogenetic testing, and privacy and antidiscrimination protections sufficient to reassure physicians and patients that genetic testing will not lead to stigmatization and discrimination.

Ethanol drinking in rodents: is free-choice drinking related to the reinforcing effects of ethanol?

Many studies have used voluntary ethanol consumption by animals to assess the influence of genetic and environmental manipulations on ethanol drinking. However, the relationship between home cage ethanol consumption and more formal assessments of ethanol-reinforced behavior using operant and instrumental conditioning procedures is not always clear. The present review attempted to evaluate whether there are consistent correlations between mouse and rat home cage ethanol drinking on the one hand, and either operant oral self-administration (OSA), conditioned taste aversion (CTA), or conditioned place preference (CPP) with ethanol on the other. We also review literature on intravenous ethanol self-administration (IVSA). To collect data, we evaluated a range of genetic manipulations that can change both genes and ethanol drinking behavior including selective breeding, transgenic and knockout models, and inbred and recombinant inbred strain panels. For a genetic model to be included in the analysis, there had to be published data resulting in differences on home cage drinking and data for at least one of the other behavioral measures. A consistent, positive correlation was observed between ethanol drinking and OSA, suggesting that instrumental behavior is closely genetically related to consummatory and ingestive behavior directed at ethanol. A negative correlation was observed between CTA and drinking, suggesting that ethanol's aversive actions may limit oral consumption of ethanol. A more modest, positive relationship was observed between drinking and CPP, and there were not enough studies available to determine a relationship with IVSA. That some consistent outcomes were observed between widely disparate behavioral procedures and genetic populations may increase confidence in the validity of findings from these assays. These findings may also have important implications when researchers decide which phenotypes to use in measuring alcohol-reward relevant behaviors in novel animal models.

Role of GABA in anxiety and depression

This review assesses the parallel data on the role of gamma-aminobutyric acid (GABA) in depression and anxiety. We review historical and new data from both animal and human experimentation which have helped define the key role for this transmitter in both these mental pathologies. By exploring the overlap in these conditions in terms of GABAergic neurochemistry, neurogenetics, brain circuitry, and pharmacology, we develop a theory that the two conditions are intrinsically interrelated. The role of GABAergic agents in demonstrating this interrelationship and in pointing the way to future research is discussed.

Alcohol: effects on neurobehavioral functions and the brain

Alcoholism results from an interplay between genetic and environmental factors, and is linked to brain defects and associated cognitive, emotional, and behavioral impairments. A confluence of findings from neuroimaging, physiological, neuropathological, and neuropsychological studies of alcoholics indicate that the frontal lobes, limbic system, and cerebellum are particularly vulnerable to damage and dysfunction. An integrative approach employing a variety of neuroscientific technologies is essential for recognizing the interconnectivity of the different functional systems affected by alcoholism. In that way, relevant experimental techniques can be applied to assist in determining the degree to which abstinence and treatment contribute to the reversal of atrophy and dysfunction.

Genetic and environmental influences on the development of alcoholism: resilience vs. risk

The physiological changes of adolescence may promote risk-taking behaviors, including binge drinking. Approximately 40% of alcoholics were already drinking heavily in late adolescence. Most cases of alcoholism are established by the age of 30 years with the peak prevalence at 18-23 years of age. Therefore the key time frame for the development, and prevention, of alcoholism lies in adolescence and young adulthood. Severe childhood stressors have been associated with increased vulnerability to addiction, however, not all stress-exposed children go on to develop alcoholism. Origins of resilience can be both genetic (variation in alcohol-metabolizing genes, increased susceptibility to alcohol's sedative effects) and environmental (lack of alcohol availability, positive peer and parental support). Genetic vulnerability is likely to be conferred by multiple genes of small to modest effects, possibly only apparent in gene-environment interactions. For example, it has been shown that childhood maltreatment interacts with a monoamine oxidase A (MAOA) gene variant to predict antisocial behavior that is often associated with alcoholism, and an interaction between early life stress and a serotonin transporter promoter variant predicts alcohol abuse in nonhuman primates and depression in humans. In addition, a common Met158 variant in the catechol-O-methyltransferase (COMT) gene can confer both risk and resilience to alcoholism in different drinking environments. It is likely that a complex mix of gene(s)-environment(s) interactions underlie addiction vulnerability and development. Risk-resilience factors can best be determined in longitudinal studies, preferably starting during pregnancy. This kind of research is important for planning future measures to prevent harmful drinking in adolescence.

Analysis of alcohol-related phenotypes in F2 progeny derived from FH/Wjd and ACI/N rat strains reveals independent measures and sex differences

Ethanol associated addictive behaviors are governed by a combination of multiple gene action (polygenic or quantitative trait) and environmental factors. We produced F2 progeny from F1 crosses derived from the alcohol-preferring Fawn-Hooded (FH/Wjd) rat strain and the alcohol-nonpreferring ACI/N strain. We compared different phenotypes related to alcohol intake in more than 600 F2 progeny. We found that female rats had significantly higher mean voluntary and forced ethanol, water, saccharin and total fluid intakes than male rats. Therefore, we compared these measures in the top 15th percentile with those in bottom 15th percentile of the F2 total ethanol intake distribution separately for males and females. The two tail comparison of means showed that only the trait of alcohol preference differed significantly in both males and females, suggesting that alcohol preference is closely related to alcohol intake. Because of the detailed information about the F1 parents of the F2 progeny, it was possible to determine parental effects. For swim test immobility, for example, the F2 progeny derived from FA(m)/FA(f) parents (ACI maternal inheritance) had the lowest mean value of 130s while the F2 progeny from AF/AF parents (FH maternal inheritance) had the highest mean value of 157s (p<0.005). The F2 progeny derived from FA/AF parents (FH maternal inheritance) showed higher mean values of forced alcohol intake than FA/FA parents (FH paternal inheritance) (6.58 and 6.36g/kg/day, respectively) suggesting that the FH mother had a significantly (p<0.0001) greater effect on forced alcohol intake than the FH father. It is concluded from these analyses that alcohol-related phenotypes are segregating independently and may be influenced by maternal and sex factors.

Nicotine-induced changes of glutamate and arginine in naive and chronically alcoholized rats: An in vivo microdialysis study

The effects of nicotine, when administered either acutely or chronically, at doses of 0.15, 0.3 or 0.6 mg/kg, on the release of glutamate and arginine in the rat nucleus accumbens have been studied in microdialysis experiments. Glutamate release significantly increased after acute nicotine injection, 0.3 mg/kg, which was accentuated if there was a priming regime of saline for the previous 27 days. This is possibly related to the rewarding effects of nicotine. Five hours after cessation of chronic oral nicotine administration, there were significant increases in glutamate content, which was possibly reflective of a withdrawal process. Significant decreases in nucleus accumbens arginine release were evident, between 1 and 2 h, after chronic nicotine administration. When nicotine was co-administered to rats during chronic ethanol intoxication, at either 0.15 mg/kg or 0.3 mg/kg doses, glutamate release did not increase during the first 12 h of withdrawal. However, a decrease in arginine microdialysate content was still observed with all nicotine doses. The nicotine-induced changes in glutamate and arginine release in nucleus accumbens highlights the complex neuropharmacological interactions evoked by this compound and also identified its possible modulating effect on glutamate release during the initial stages of chronic ethanol withdrawal.

Using ancestry-informative markers to define populations and detect population stratification

A serious problem with case-control studies is that population subdivision, recent admixture and sampling variance can lead to spurious associations between a phenotype and a marker locus, or indeed may mask true associations. This is also a concern in therapeutics since drug response may differ by ethnicity. Population stratification can occur if cases and controls have different frequencies of ethnic groups or in admixed populations, different fractions of ancestry, and when phenotypes of interest such as disease, drug response or drug metabolism, also differ between ethnic groups. Although most genetic variation is inter-individual, there is also significant inter-ethnic variation. The International HapMap Project has provided allele frequencies for approximately three million single nucleotide polymorphisms (SNPs) in Africans, Europeans and East Asians. SNP variation is greatest in Africans. Statistical methods for the detection and correction of population stratification, principally Structured Association and Genomic Control, have recently become freely available. These methods use marker loci spread throughout the genome that are unlinked to the candidate locus to estimate the ancestry of individuals within a sample, and to test for and adjust the ethnic matching of cases and controls. To date, few case-control association studies have incorporated testing for population stratification. This paper will focus on the debate about the quantity and methods for selection of highly informative marker loci required to characterize populations that vary in substructure or the degree of admixture, and will discuss how these theoretically desirable approaches can be effectively put into practice.

Moderate-to-heavy alcohol intake is associated with differences in synchronization of brain activity during rest and mental rehearsal

In alcohol-dependent individuals, synchronization of brain activity is different from that in non-alcohol-dependent individuals as reflected by EEG differences at alpha and beta frequencies (8-30 Hz). These EEG differences may not only be related to long-term alcohol intake but also to genetic factors that are associated with alcohol dependence. Thus, it is not known what the pure effect of long-term alcohol intake on synchronization of brain activity is. Therefore, we investigated whether EEG synchronization differs between light (0.5-6 drinks per week), moderate (7-20 drinks per week), and heavy (21-53 drinks per week) drinkers. All participants (49 males and 47 females) were free of a personal and family history of alcohol dependence. Eyes-closed EEG was recorded at rest and during mental rehearsal of pictures. EEG synchronization was determined by computing Synchronization Likelihood for six frequency bands (0.5-4 Hz, 4-8 Hz, 8-12 Hz, 12-20 Hz, 20-30 Hz, 30-45 Hz). Both male and female heavy drinkers displayed a loss of lateralization in alpha (8-12 Hz) and slow-beta (12-20 Hz) synchronization. In addition, moderately and heavily drinking males had lower fast-beta (20-30 Hz) synchronization than lightly drinking males. It is concluded that both male and female drinkers who drink 21 alcoholic drinks per week or more have impaired synchronization of brain activity during rest and mental rehearsal at alpha and beta frequencies as compared to individuals who drink less. As individuals with a personal or family history of alcohol dependence were excluded, the confounding effects of genetic factors related to alcohol dependence on synchronization of brain activity were minimized.

Acamprosate for the treatment of alcohol dependence

BACKGROUND

Both inpatient and outpatient treatment centers that focus solely on psychosocial therapies for the treatment of alcohol dependence have high relapse rates. Thus, extensive research has focused on the development of pharmacologic moieties to attenuate the craving for alcohol after acute alcohol detoxification. Three drug therapies are currently approved by the US Food and Drug Administration (FDA) for this purpose: disulfiram, naltrexone, and acamprosate. The latter was approved by the FDA in 2004.

OBJECTIVE

This article describes the pharmacologic properties and clinical usefulness of acamprosate for the treatment of alcohol dependence.

METHODS

Relevant information was identified through searches of MEDLINE (1966 to March 2005), International Pharmaceutical Abstracts (1970-2005), Current Contents (1996-2005), and Cumulative Index to Nursing and Allied Health Literature (1982-Week 2, 2004) using the key words acamprosate, alcohol dependence, and alcoholism (MeSH).

RESULTS

Acamprosate limited to randomized, controlled clinical trials yielded 33 hits in MEDLINE. Twenty-two articles were reviewed for efficacy end points, and 10 were reviewed for pharmacology and pharmacokinetics data. Acamprosate plus pharmacokinetics and pharmacodynamics yielded 19 hits, some of which were duplicates from the previously described search. Acamprosate plus meta-analysis (MeSH) yielded 5 hits, naltrexone plus meta-analysis (MeSH) yielded 9 hits, and disulfiram plus meta-analysis yielded 3 hits. The most recent review articles and their reference lists were assessed to ensure completeness of literature searches. Based on these searches, acamprosate is known to be an analogue of taurine and gamma-aminobutyric acid (GABA), 2 central nervous system neuromodulators. Acamprosate is thought to share some of the cellular actions of taurine affecting GABA and glutaminergic receptors in the nucleus accumbens, a brain region that may be responsible for the reinforcing effects received after alcohol consumption. Acamprosate is thought to also suppress excitation-induced calcium entry that results from chronic alcohol exposure, thereby altering the conformation of the N-methyl-d-aspartate receptors. The percentage of patients taking acamprosate who were completely abstinent throughout the different durations of the studies varied from approximately 18% to 61%, compared with 4% to 45% with placebo. Diarrhea was the most common adverse effect accompanying acamprosate therapy, and this was generally described as dose related and transient.

CONCLUSIONS

Acamprosate is associated with modest treatment effects. Its efficacy is similar to naltrexone, and the combination of acamprosate and naltrexone appears to be more efficacious than acamprosate alone, when combined with psychosocial interventions.

Health risks of chronic moderate and heavy alcohol consumption: how much is too much?

This article presents the proceedings of a symposium held at the meeting of the International Society for Biomedical Research on Alcoholism (ISBRA) in Mannheim, Germany, in October 2004. Most of what we know about the deleterious effects of alcohol in vivo has been gleaned from studies in sober alcoholics recruited from substance abuse treatment programs. Little is known about effects of chronic drinking in the moderate or heavy range encountered in a much larger fraction of modern society. Extrapolation of information on the adverse effects of chronic drinking on organ function from clinical samples to social drinkers in the general population has to be met with great skepticism, as it may lead to wrong conclusions about the chronic effects of alcohol in social drinkers. Several recent studies suggest that moderate alcohol consumption has certain beneficial health effects, whereas heavy social alcohol consumption has recently been associated with organ abnormalities and cognitive deficits. These social drinking effects have attracted great public interest; reports of benefits of moderate drinking have also inspired inappropriate publications by the media, including misleading advertisements by the alcohol producing and distributing industry. Although adverse effects of moderate to heavy drinking on heart, liver, and cancer development have attracted attention by clinicians and researchers for some time, its compromising effects on brain and cognition have only recently been studied. This symposium brought together researchers from different disciplines, who reviewed and presented new data on consequences of social drinking in the areas of clinical neuropsychology and behavior (Drs. Nixon and Meyerhoff), neurophysiology (Dr. Nixon, Ms. De Bruin), neuroimaging (Ms. de Bruin, Dr. Meyerhoff), hepatic disease (Dr. Bode), and cancer (Dr. Seitz). The symposium aimed to clarify both the potential health benefits of moderate alcohol consumption and risks of moderate and heavy drinking on proper organ function and to provide insights and new data to practicing physicians and public health authorities for education on problem drinking.

Deficits in amygdaloid cAMP-responsive element-binding protein signaling play a role in genetic predisposition to anxiety and alcoholism

We investigated the role of cAMP-responsive element-binding protein (CREB) in genetic predisposition to anxiety and alcohol-drinking behaviors using alcohol-preferring (P) and -nonpreferring (NP) rats. The levels of CREB, phosphorylated CREB, and neuropeptide Y (NPY) were innately lower in the central amygdala (CeA) and medial amygdala (MeA), but not in the basolateral amygdala (BLA), of P rats compared with NP rats. P rats displayed higher baseline anxiety-like behaviors and consumed higher amounts of alcohol compared with NP rats. Ethanol injection or voluntary intake reduced the higher anxiety levels in P rats. Ethanol also increased CREB function in the CeA and MeA, but not in the BLA, of P rats. Infusion of the PKA activator Sp-cAMP or NPY into the CeA decreased the alcohol intake and anxiety-like behaviors of P rats. PKA activator infusion also increased CREB function in the CeA of P rats. On the other hand, ethanol injection or voluntary intake did not produce any changes either in anxiety levels or on CREB function in the amygdaloid structures of NP rats. Interestingly, infusion of the PKA inhibitor Rp-cAMP into the CeA provoked anxiety-like behaviors and increased alcohol intake in NP rats. PKA inhibitor decreased CREB function in the CeA of NP rats. These novel results provide the first evidence to our knowledge that decreased CREB function in the CeA may be operative in maintaining the high anxiety and excessive alcohol-drinking behaviors of P rats.

Associations between alcohol intake and brain volumes in male and female moderate drinkers

BACKGROUND

Alcohol-dependent individuals have brain volume loss. Possibly, moderate drinkers who are not alcohol dependent have similar but less prominent brain damage. The authors investigated whether current or lifetime alcohol intake is related to volumes of total brain, cerebellum, ventricles, peripheral cerebrospinal fluid, and cerebral gray and white matter in moderate drinkers.

METHODS

The relation between current or lifetime alcohol intake and brain volumes of 47 male moderate drinkers (current alcohol intake 20 drinks per week, lifetime alcohol intake 240 kg) and 44 female moderate drinkers (current alcohol intake 15 drinks per week, lifetime alcohol intake 170 kg), all without a personal or family history of alcohol dependence, was determined using high-resolution magnetic resonance images, corrected for intracranial volume, age, and sex.

RESULTS

In males, mean lifetime alcohol intake was positively associated with cerebral white matter volume, particularly in the frontal region. In females, mean lifetime alcohol intake was not associated with brain volumes. Current alcohol intake was unrelated to brain volumes in either males or females.

CONCLUSIONS

Neither current nor lifetime alcohol intake is associated with decreases in brain volumes in male or female moderate drinkers. Because all participants had a negative personal and family history of alcohol dependence, the current results relatively purely concern the effects of moderate alcohol intake on brain volumes.

Association between the serotonin transporter gene and alcohol consumption in social drinkers

Relatively few studies have investigated the role of the 5HTT gene in intermediate phenotypes such as alcohol consumption in non-alcohol dependent populations. A recent study reported an association with alcohol consumption in a student population. We attempted to replicate these findings and extend on this work in a representative, ethnically homogenous, non-alcohol dependent sample of social drinkers in the United Kingdom. The short allele of the 5HTT gene was significantly associated with increased alcohol consumption (P = 0.03). There was suggestive evidence of a genotype-sex interaction (P = 0.04). Post-hoc tests indicated higher alcohol consumption in men with one or more copies of the short allele, while in women consumption was highest among heterozygotes compared to both homozygote groups. Age at time of data collection and cigarette consumption were entered as covariates. These results replicate recent previous findings and suggest a possibility that this association may differ in men and women.

Genetic susceptibility to substance dependence

Despite what is often believed, the majority of those who experiment with substances with a dependence potential do not develop dependence. However, there is a subpopulation of users that easily becomes dependent on substances, and these individuals exhibit pre-existing comorbid traits, including novelty seeking and antisocial behavior. There appears to be a genetic basis for the susceptibility to dependence and these comorbid traits. Animal studies have identified specific genes that can alter susceptibility to dependence and response to novelty. The mechanisms underlying the genetic susceptibility to dependence and response to novelty are complex, but genetic susceptibility plays a significant role in the transition from substance use to dependence and from chronic use to addiction. We discuss two models to explain how genetic variations alter dependence susceptibility. Identification of the specific genes involved in these processes would help to identify individuals that are vulnerable to dependence/addiction and to devise novel treatment strategies.

Combining research approaches to advance our understanding of drug addiction

Drug addiction is a complex behavior, likely to be influenced by various genes, environmental factors, and gene-gene and gene-environment interactions. Various aspects of addiction are studied by different disciplines. Animal studies are increasing insight into brain regions and genes associated with addiction. Epidemiologic studies are establishing the factors increasing risk for initiation and continuation of substance use. Twin and adoption studies are increasing our understanding of the complex mechanisms involved in substance use, including comorbidity and gene environment interaction. Finally, molecular genetic studies in humans are starting to yield some converging findings. It is argued and illustrated with examples that greater awareness of progress in other disciplines can speed up our understanding of the complex processes involved in addiction. This should help our ability to identify who is at increased risk of becoming addicted and the development of prevention and intervention strategies targeted at an individual's specific needs.