Changes in Gene Expression within the Ventral Tegmental Area Following Loss-of-Control Alcohol Drinking by Alcohol-Preferring (P) Rats

The objective of this study was to determine changes in gene expression in the ventral tegmental area (VTA) following loss-of-control alcohol drinking by alcohol-preferring (P) rats. Adult female P rats (n = 7) were given concurrent access to 10, 20 and 30% EtOH for four 1-hr sessions daily for 10 weeks followed by 2 cycles of 2 weeks of abstinence and 2 weeks of EtOH access. Rats were killed by decapitation 3 hr after the 4th daily EtOH-access session at the end of the second 2-week relapse period. An age-matched water control group of female P rats (n = 8) was also killed. RNA was prepared from micropunch samples of the VTA from individual rats; analyses were conducted with Affymetrix Rat 230.2 chips. Ethanol intakes were 1.5-2.5 g/kg per sessions, resulting in blood levels >200 mg% at the end of the 4th session. There were 211 named genes that were significantly different (FDR = 0.1) between the water and EtOH groups. Bioinformatics analyses indicated alterations in (a) transcription factors that reduced excitation-coupled transcription and promoted exocitotic neuronal damage involving clusters of genes associated with Nfkbia, Fos and Srebf1; (b) genes that reduced cholesterol and fatty acid synthesis, and increased protein degradation; and (c) genes involved in cell-to-cell interactions and regulation of the actin cytoskeleton. Among the named genes, there were 62 genes in common with differences between alcohol-naïve P and non-preferring (NP) rats, with 43 of the genes changing in the opposite direction following excessive binge-like drinking. These genes are involved in a pro-inflammatory response, and enhanced response to glucocorticoids and steroid hormones. Overall, the results of this study indicated that excessive binge-like alcohol drinking by P rats may be altering the expression of genes that promote neuronal damage.本研究旨在探究偏爱酒精（alcohol-preferring, P）大鼠发生失控性饮酒后，腹侧被盖区（ventral tegmental area, VTA）的基因表达变化。实验选取成年雌性P大鼠（n=7），每日使其同时接触10%、20%及30%乙醇（ethanol, EtOH），每次接触时长1小时，每日进行4次接触实验，持续10周；随后经历2个循环周期，每个周期包含2周戒断与2周乙醇接触。在第二个2周复饮周期结束时，于每日第4次乙醇接触实验结束后3小时，采用断头法处死大鼠。同时设置年龄匹配的雌性P大鼠饮水对照组（n=8），并以相同方式处死。从单只大鼠的VTA微穿刺样本中提取RNA，使用Affymetrix Rat 230.2芯片开展基因表达分析。 单次乙醇接触实验中，大鼠乙醇摄入量为1.5~2.5 g/kg，第4次接触结束时血液乙醇浓度超过200mg%。饮水对照组与乙醇暴露组间共存在211个表达显著差异的命名基因（错误发现率False Discovery Rate, FDR=0.1）。生物信息学分析显示，差异基因涉及三类改变：(a) 转录因子相关通路：此类转录因子可减弱兴奋-偶联转录过程，并促进兴奋性神经元损伤，其关联的基因簇涉及Nfkbia、Fos及Srebf1；(b) 参与胆固醇与脂肪酸合成抑制、蛋白质降解增强的基因；(c) 参与细胞间相互作用及肌动蛋白细胞骨架调控的基因。 在上述命名差异基因中，有62个基因与酒精初次接触P大鼠与非偏爱酒精（non-preferring, NP）大鼠间的差异基因重合，其中43个基因在过量暴饮样饮酒后表达变化方向相反。此类基因涉及促炎反应、糖皮质激素与类固醇激素应答增强。 综上，本研究结果表明，P大鼠的过量暴饮样饮酒行为可能改变促进神经元损伤的基因表达。