Stress regulation of sustained attention and the cholinergic attention system

Background: Stress exacerbates symptoms of schizophrenia and attention deficit hyperactivity disorder, which are characterized by impairments in sustained attention. Yet how stress regulates attention remains largely unexplored. Here we investigated whether a 6-day variable stressor (VS) altered sustained attention and the cholinergic attention system in male and female rats. Methods: Sustained attention was tested with the sustained attention task (SAT). Successful performance on SAT relies on the release of acetylcholine (ACh) into the cortex from cholinergic neurons in the nucleus basalis of Meynert (NBM). Thus, we evaluated whether VS altered the morphology of these neurons with a novel approach using Cre-dependent virus in genetically modified ChAT::Cre rats, a species used for this manipulation only. Next, electrochemical recordings measured cortical ACh following VS. Finally, we used RNAseq to identify VS-induced transcriptional changes in the NBM. Results: VS impaired attentional performance in SAT and increased the dendritic complexity of NBM cholinergic neurons in both sexes. NBM cholinergic neurons are mainly under inhibitory control, so this morphological change could increase inhibition on these neurons, reducing downstream ACh release to impair attention. Indeed, VS decreased ACh release in the prefrontal cortex of males. Quantification of global transcriptional changes revealed that, although VS induced many sex-specific changes in gene expression, it increased several signaling molecules in both sexes. Overall design: Transcription profiles of NBM in rats undergo VS were generated by deep sequencing, in six replicates, using Hiseq 4000

背景：压力会加重精神分裂症与注意缺陷多动障碍的症状，这两类疾病均以持续性注意（sustained attention）功能受损为典型特征。然而，压力调控注意的具体机制仍未得到充分探索。本研究旨在探究6天可变应激（variable stressor, VS）是否会改变雌雄大鼠的持续性注意功能与胆碱能注意系统（cholinergic attention system）。
方法：采用持续性注意任务（sustained attention task, SAT）评估大鼠的持续性注意能力。SAT任务的成功完成依赖于梅纳特基底核（nucleus basalis of Meynert, NBM）内胆碱能神经元向皮层释放乙酰胆碱（acetylcholine, ACh）。为此，我们通过一种全新方法——对基因修饰的胆碱乙酰转移酶-Cre（ChAT::Cre）大鼠使用Cre依赖型病毒（Cre-dependent virus），评估VS是否改变了此类神经元的形态，该品系大鼠此前仅被应用于此类实验操作。随后，通过电化学记录检测VS暴露后皮层内的乙酰胆碱水平变化。最后，采用RNA测序（RNA-seq）技术鉴定NBM组织中VS诱导的转录组改变。
结果：VS损伤了大鼠在SAT任务中的注意表现，并同时增加了雌雄大鼠NBM胆碱能神经元的树突复杂性。NBM胆碱能神经元主要受抑制性调控，因此这种形态学改变可能会增强对这些神经元的抑制作用，进而减少下游乙酰胆碱释放，最终损伤注意功能。实验结果证实，VS会降低雄性大鼠前额叶皮层内的乙酰胆碱释放量。对全局转录组变化的定量分析显示，尽管VS诱导了大量性别特异性的基因表达改变，但它在两种性别的大鼠中均上调了多种信号分子的表达。
整体实验设计：通过HiSeq 4000平台开展高通量测序，对经VS处理的大鼠NBM组织进行转录组分析，共设置6个生物学重复。