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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