Several studies have shown the opioid antagonist naltrexone to be effective when combined with psychosocial therapies for the treatment of patients who are dependent on alcohol with fixed medication and time (12 weeks). In this study, 121 nonabstinent outpatients with alcohol dependence (DSM-IV) were treated with sessions of cognitive coping skills (N = 67) or supportive therapy (N = 54) and either naltrexone 50 mg/day (N = 63) or placebo (N = 58) daily for the first 12 weeks and thereafter for 20 weeks only when craving alcohol (i.e., targeted medication) in a prospective one-center, dual, double-blind, randomized clinical trial. The dropout rate for all subjects was 16.5% during the first 12-week period and approximately twice that level by the end of the study. There were no significant group differences in study completion and therapy participation rates. After the continuous medication (12 weeks), the coping/naltrexone group had the best outcome, and coping/placebo had the worst. This difference remained during the targeted medication period (the following 20 weeks). Naltrexone was not better than placebo in the supportive groups, but it had a significant effect in the coping groups: 27% of the coping/naltrexone patients had no relapses to heavy drinking throughout the 32 weeks, compared with only 3% of the coping/placebo patients. The authors' data confirm the original finding of the efficacy of naltrexone in conjunction with coping skills therapy. In addition, their data show that detoxification is not required and that targeted medication taken only when craving occurs is effective in maintaining the reduction in heavy drinking.

The AA (alko, alcohol) and ANA (alko, non-alcohol) rat lines were among the earliest rodent lines produced by bidirectional selection for ethanol preference. The purpose of this review is to highlight the strategies for understanding the neurobiological factors underlying differential alcohol-drinking behavior in these lines. Most early work evaluated functioning of the major neurotransmitter systems implicated in drug reward in the lines. No consistent line differences were found in the dopaminergic system either under baseline conditions or after ethanol challenges. However, increased opioidergic tone in the ventral striatum and a deficiency in endocannabinoid signaling in the prefrontal cortex of AA rats may comprise mechanisms leading to increased ethanol consumption. Because complex behaviors, such as ethanol drinking, are not likely to be controlled by single factors, system-oriented molecular-profiling strategies have been used recently. Microarray based expression analysis of AA and ANA brains and novel data-mining strategies provide a system biological view that allows us to formulate a hypothesis on the mechanism underlying selection for ethanol preference. Two main factors appear active in the selection: a recruitment of signal transduction networks, including mitogen-activated protein kinases and calcium pathways and involving transcription factors such as Creb, Myc and Max, to mediate ethanol reinforcement and plasticity. The second factor acts on the mitochondrion and most likely provides metabolic flexibility for alternative substrate utilization in the presence of low amounts of ethanol.

The results confirm previous results which showed that both mu- and delta-opioid receptors are involved in the regulation of ethanol self-administration and indicate that genetic differences between AA and Wistar rats produced by selection do not modify the effects of opioid antagonists. The nucleus accumbens and the basolateral amygdala may be important central sites for the mediation of their suppressive effects.

A quantitative genetic approach, which involves correlation of transcriptional networks with the phenotype in a recombinant inbred (RI) population and in selectively bred lines of rats, and determination of coinciding QTLs for gene expression and the trait of interest, has been applied in the current study. In this analysis, a novel approach was used that combined DNA-Seq data, data from brain exon array analysis of HXB/BXH RI rat strains and six pairs of rat lines selectively bred for high and low alcohol preference, and RNA-Seq data (including rat brain transcriptome reconstruction) to quantify transcript expression levels, generate co-expression modules, and identify biological functions that contribute to the predisposition to consume varying amounts of alcohol. A gene co-expression module was identified in the RI rat strains that contained both annotated and unannotated transcripts expressed in brain, and was associated with alcohol consumption in the RI panel. This module was found to be enriched with differentially expressed genes from the selected lines of rats. The candidate genes within the module and differentially expressed genes between high and low drinking selected lines were associated with glia (microglia and astrocytes), and could be categorized as being related to immune function, energy metabolism and calcium homeostasis, and glial-neuronal communication. Our results illustrate that there are multiple combinations of genetic factors that can produce the same phenotypic outcome. While no single gene accounts for predisposition to a particular level of alcohol consumption in every animal model, coordinated differential expression of subsets of genes in the identified pathways produce similar phenotypic outcomes.

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The purpose of the present study was to investigate the role of ventral pallidal opioidergic mechanisms in the control of ethanol intake by studying the effects of acute administration of morphine on the levels of GABA, glutamate, and dopamine in the ventral pallidum. The study was conducted using the alcohol-preferring Alko Alcohol (AA) and alcohol-avoiding Alko Non-Alcohol (ANA) rat lines that have well-documented differences in their voluntary ethanol intake and brain opioidergic systems. Therefore, examination of neurobiological differences between the lines is supposed to help to identify the neuronal mechanisms underlying ethanol intake, since selection pressure is assumed gradually to lead to enrichment of alleles promoting high or low ethanol intake, respectively. The effects of an acute dose of morphine (1 or 10 mg/kg s.c.) on the extracellular levels of GABA and glutamate in the ventral pallidum were monitored with in vivo microdialysis. The concentrations of GABA and glutamate in the dialyzates were determined with a high performance liquid chromatography system using fluorescent detection, while electrochemical detection was used for dopamine. The levels of glutamate in the rats injected with morphine 1 mg/kg were significantly above the levels found in the controls and in the rats receiving morphine 10 mg/kg. Morphine 10 mg/kg also increased the levels of dopamine. Morphine could not, however, modify the levels of GABA. The rat lines did not differ in any of the effects of morphine. The data suggest that the glutamatergic and dopaminergic systems in the ventral pallidum may mediate some effects of morphine. Since there were no differences between the AA and ANA lines, the basic hypothesis underlying the use of the genetic animal model suggests that the effects of morphine detected probably do not underlie the different intake of ethanol by the lines and contribute to the control of ethanol intake in these animals.

The offspring of rats that voluntarily select larger quantities of alcohol are heavier consumers of alcohol than the offspring of rats that tend to avoid it. Such selective breeding, repeated over many generations, was used to develop the AA (Alko, Alcohol) line of rats which prefer 10% alcohol to water, and the ANA (Alko, Non-Alcohol) line of rats which choose water to the virtual exclusion of alcohol. In addition to demonstrating the likely role of genetic factors in alcohol consumption, these lines have been used to find behavioral, metabolic, and neurochemical correlates of differential alcohol intake. Some of the line differences that have been found involve the reinforcing effects of ethanol, the changes in consumption produced by alcohol deprivation and nutritional factors, the behavioral and adrenal monoamine reactions to mild stress, the development of tolerance, the accumulation of acetaldehyde during ethanol metabolism, and the brain levels of serotonin. It is hoped that these studies will lead to a better understanding of the genetically-determined mechanisms that influence the selection of alcohol.

Analyzing gene expression patterns in genetic models of alcoholism may uncover previously unknown susceptibility genes, and point to novel targets for drug development. Here, we compared expression profiles in alcoholpreferring AA rats with the alcohol-avoiding counterpart ANA line, and unselected Wistar rats. Cingulate cortex, Nc. accumbens, amygdala and hippocampus of each line were analyzed using the Afymetrix RN U34 arrays and dChip 1.1 software. Analysis of line-specific expression revealed 48 differentially expressed genes between AA and ANA rats. Elevated hippocampal neuropeptide Y (NPY) was found in ANA rats in agreement with previous studies. A cluster of MAP-kinases indicating altered signal transduction was upregulated within the Nc. Accumbens of the AA line, and is of particular functional interest. Within the amygdala, a more loosely inter-related cluster of cytoskeleton-associated genes may point to structural abnormalities. The observed dysregulations may contribute to the alcohol-preferring phenotype.