Outbred rats differentially consume alcohol when having free access to it. Among others, BDNF (brain-derived neurotrophic factor) is believed to control voluntary ethanol intake in rodents. Meanwhile, expression of BDNF exons in brain regions and epigenetic mechanisms underlying alcohol intake pattern remain obscure. The main goal was to study whether voluntary alcohol drinking pattern affects expression of BDNF exons in selected rat brain regions during early abstinence. Intermittent access to 20% ethanol in a two-bottle-choice procedure (IA2BC) was used as a model of voluntary ethanol intake. Male Wistar rats (n = 24) had twenty 24-h sessions of free access to two-bottle choice (water or 20% ethanol) with 24-h withdrawal periods (water only). Control animals had access to water only (n = 11). After finishing IA2BC, the animals were divided according to the compliance of ethanol intake pattern with gradual escalation, a key feature of the paradigm. To access potential behavioral disturbances during the early abstinence, rats were consequently tested in the open field test, the elevated plus-maze, and the sucrose preference test. On the third day after the last drinking session, expression of BDNF exons and polypeptide was measured in the frontal cortex, hippocampus, striatum, and midbrain using quantitative PCR and Western blotting, respectively. Additionally, chromatin immunoprecipitation was performed to analyze enrichment of positive Ph-CREB (Ser133) and negative EZH2 transcriptional regulators as well as markers of active H3K9ac and repressed H3K27me3 chromatin at exon-specific BDNF promoters in brain regions with affected BDNF expression. During the course of the IA2BC, one part of animals demonstrated gradual escalation from low to high alcohol intake and preference of alcohol over water (a typical pattern for IA2BC) while the other one consumed alcohol at a consistently high level (an unusual pattern for IA2BC). Drinking pattern in the IA2BC does not define differences of behavior in any of the tests during early abstinence. Finally, the IA2BC rats with growing alcohol intake showed elevation of BDNF mRNA containing exon VI in the hippocampus associated with an enhanced H3K9ac occupancy at the respective promoter. Thus, rats differentially consuming alcohol in the IA2BC paradigm differ in epigenetically determined expression of BDNF exon VI in the hippocampus during early abstinence.

远交的大鼠在自由获取酒精时会差异化地消耗酒精。其中，BDNF（脑源性神经营养因子）被认为可以控制啮齿动物的自愿乙醇摄入量。同时，BDNF 外显子在大脑区域的表达和酒精摄入模式的表观遗传机制仍然不清楚。主要目标是研究自愿饮酒模式是否会影响早期戒酒期间选定大鼠大脑区域中 BDNF 外显子的表达。在两瓶选择程序 (IA2BC) 中间歇性获得 20% 乙醇被用作自愿摄入乙醇的模型。雄性 Wistar 大鼠 ( n  = 24) 有 20 次 24 小时免费使用两瓶选择（水或 20% 乙醇）和 24 小时停药期（仅水）。对照动物只能喝水（n = 11）。完成 IA2BC 后，根据乙醇摄入模式的依从性对动物进行划分，逐渐升级，这是范式的一个关键特征。为了在早期禁欲期间获得潜在的行为障碍，因此在露天试验、高架十字迷宫和蔗糖偏好试验中对大鼠进行了测试。在最后一次饮酒后的第三天，分别使用定量 PCR 和蛋白质印迹法测量额叶皮层、海马、纹状体和中脑中 BDNF 外显子和多肽的表达。此外，进行染色质免疫沉淀以分析阳性 Ph-CREB ​​(Ser133) 和阴性 EZH2 转录调节因子以及活性 H3K9ac 和受抑制的 H3K27me3 染色质标记物在外显子特异性 BDNF 启动子处的富集。在 IA2BC 的过程中，一部分动物表现出从低酒精摄入量到高酒精摄入量的逐渐增加和对酒精的偏好（IA2BC 的典型模式），而另一只动物则以持续高水平饮酒（IA2BC 的一种不寻常模式） ）。IA2BC 中的饮酒模式并没有定义早期戒酒期间任何测试中的行为差异。最后，酒精摄入量增加的 IA2BC 大鼠显示海马中含有外显子 VI 的 BDNF mRNA 升高，这与相应启动子的 H3K9ac 占有率增加有关。因此，在 IA2BC 范式中差异饮酒的大鼠在早期戒酒期间海马中表观遗传决定的 BDNF 外显子 VI 表达不同。