Caracterização molecular e comportamental de um modelo animal de consumo de etanol

Abstract

For the first time, we have demonstrated the relation between genes responsible for energy metabolism of the brain, genes of GABAergic pathway and addictive behavior in an animal model. We used non-inbred, Swiss mice exposed to a three-bottle free-choice model (water, 5% v/v ethanol, and 10% v/v ethanol) over a long period consisting of four phases: acquisition (AC), withdrawal (W), reexposure (RE) and quinine-adulteration (AD). Later, mice were behaviorally classified into three groups: loss-of-control-drinker (A; preference for ethanol and high levels of consumption during all phases), heavy drinker (H; preference for ethanol and high levels of consumption during AC and reduction in AD), and light drinker (L; preference for water during all phases). Microarray analysis using total RNA from nucleus of the amygdale showed the fatty acid metabolism pathway affected by ethanol treatment. Further analysis using quantitative real-time polymerase chain reaction among genes differentially expressed, showed that gene Acss2 was upregulated only in loss-of-control mice. Likewise, in these mice there was a significant inverse correlation between transcript levels of Hadh gene and other genes of energy metabolism in the same area, suggesting that this pathway may contribute to ethanol consumption in the loss-of-control mice. To evaluate the involvement of GABAB receptor, the mRNA of the genes Gabbr1 and Gabbr2 was quantified using real-time polymerase chain reaction in the prefrontal cortex, hypothalamus, hippocampus, and striatum. In the prefrontal cortex of animals in group A, we found high Gabbr1 and Gabbr2 transcript levels, with significantly higher Gabbr1 transcript levels compared with Groups C (control), L, and H. In the hippocampus of animals in Group A, Gabbr2 mRNA levels were significantly lower compared with Groups C, L, and H. In the striatum, we found a significant increase in Gabbr1 transcription compared with Groups C, L, and H. No differences in Gabbr1 or Gabbr2 transcript levels in the hypothalamus were observed among groups. Considering that brain areas analyzed are relevant to drug taking behavior, our results suggest that these genes may contribute to high and persistent ethanol consumption in group A. Moreover, the study of cerebral energy metabolism and GABAB receptor may provide further insight into neuronal plasticity associated with alcoholism.