Prolonged exposure of the brain to ethanol is a prerequisite for developing ethanol dependence, but the underlying neural adaptations are unknown. Here we demonstrate that rats subjected to repeated cycles of intoxication and withdrawal develop a marked and long-lasting increase in voluntary ethanol intake. Exposure-induced but not spontaneous alcohol intake is antagonized by acamprosate, a compound clinically effective in human alcoholism. Expression analysis of cingulate cortex and amygdala reveals a set of long-term up-regulated transcripts in this model. These include members of pathways previously implicated in alcohol dependence (glutamatergic, endocannabinoid, and monoaminergic neurotransmission), as well as pathways not previously thought to be involved in this disorder (e.g., members of the mitogen-activated protein kinase pathway). Thus, alternating periods of ethanol intoxication and withdrawal are sufficient to induce an altered functional brain state, which is likely to be encoded by long-term changes in gene expression. These observations may have important implications for how alcoholism is managed clinically. Novel clinically effective treatments may be possible to develop by targeting the products of genes found to be regulated in our model.

The long-term treatment outcome shows that stimulants are effective in adult ADHD and side effects tend to be mild.

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.

Identification of genes that are differentially expressed in rats bidirectionally selected for alcohol preference might reveal biological mechanisms underlying alcoholism or related phenotypes. Microarray analysis from medial prefrontal cortex (mPFC), a key brain region for drug reward, indicated increased expression of glutathione-S-transferases of the alpha (Gsta4) and mu (Gstm1-5) classes in ethanol-preferring AA rats compared with nonpreferring ANA rats. Real-time RT polymerase chain reaction (RT-PCR) analysis demonstrated approximately 2-fold higher Gsta4 transcript levels in several brain regions of ethanol-naive AA compared with ANA rats. Differences in mRNA levels were accompanied by differential levels of GSTA4 protein. We identified a novel haplotype variant in the rat Gsta4 gene, defined here as var3. Allele frequencies of var3 were markedly different between AA and ANA rats, 52% and 100%, respectively. Gsta4 expression was strongly correlated with the gene dose of var3, with approximately 60% of the variance in expression accounted for by genotype at this locus. The contribution of glutathione S-transferase expression to the ethanol-preferring phenotype is presently unclear. It could, however, underlie observed differences in life span between AA and ANA lines, prompting a utility of this animal model in aging research.

Ethanol preference and behavioral disinhibition in AA (alcohol accepting) animals is a behavioral constellation similar to that seen in human type II alcoholism, for which considerable genetic loading has been shown. In search of novel neural substrates for this phenotype, we compared gene expression in the cerebral cortex of the AA rat with two groups of control animals, the ANA (alcohol non-accepting) line and heterogeneous Wistar animals, by differential display RT-PCR. We identified two transcripts, ribosomal protein L18a mRNA and diacyglycerol kinase iota mRNA, which are differentially expressed between AA and ANA rats. Ribosomal protein L18A mRNA is evenly expressed throughout the brain, but strongly reduced in cortex of AA rats vs controls. Diacylglycerol kinase iota is exclusively found in the brain, and expressed in a distinct regional pattern. Its cortical expression is about 25% higher in AA than ANA rats. Differential display RT-PCR seems to provide a feasible strategy to identify previously unknown genes whose differential expression correlates with behavioral phenotypes related to dependence. Molecular Psychiatry (2001) 6, 103-108.Genetic factors play an important role in human alcoholism, and alcohol preference in experimental animals. 1-4 Several alcohol-preferring rat lines have been established through selective breeding for high ethanol consumption, and used to search for potential biological substrates of alcoholism. [5][6][7] Early lesion studies have shown that the cerebral cortex plays a major role in regulating alcohol self-administration in rats. 8 Following this finding, biochemical studies identified elevated levels of noradrenaline, but suppressed levels of serotonin as well as dopamine in the cortex of alcohol-preferring P-rats. 9 More recent studies have also indicated that measures of both glutamatergic and GABA-ergic transmission in the cerebral cortex have co-segregated with ethanol preference, and are also differentially affected by ethanol exposure, in two other genetic models. 10,11 In the brains of AA rats, increased levels of dopamine and serotonin have been found. 5 Differences in the opioid system between AA rats and their genetic counterparts, ANA rats have been reported. 12-14 Also, ANA rats have a decreased ethanol metabolism in the liver and certain brain areas compared to the AA line. 5 These studies have focused on specific pathways, eg brain reward or ethanol metabolism. Strategies of this type require a priori knowledge or assumptions about factors underlying the behaviors under study. Recently, accumulating sequence information and development of molecular techniques has allowed a set of complementary strategies to be applied. These attempt to identify novel candidate genes by comparing expression profiles between disease phenotypes, or models thereof. 15 Here we explored the feasibility of such a technology, differential display (DD) RT-PCR, to screen for variations in expression potentially related to alcohol preference. We compared baseline mRNA expression prof...