Tracheal occlusion conditioning in conscious rats modulates gene expression profile of medial thalamus

The thalamus may be the critical brain area involved in sensory gating and the relay of respiratory mechanical information to the cerebral cortex for the conscious awareness of breathing. We hypothesized that respiratory mechanical stimuli in the form of tracheal occlusions would modulate the gene expression profile of the thalamus. Specifically, it was reasoned that conditioning to the respiratory loading would induce a state change in the medial thalamus consistent with a change in sensory gating and the activation of molecular pathways associated with learning and memory. In addition, respiratory loading is stressful and thus should elicit changes in gene expressions related to stress, anxiety, and depression. Rats were instrumented with inflatable tracheal cuffs. Following surgical recovery, they underwent ten days (5 days/week) of transient tracheal occlusion conditioning. On day 10, the animals were sacrificed and the brains removed. The medial thalamus was dissected and microarray analysis of gene expression performed. Tracheal obstruction conditioning modulated a total of 661 genes (p < 0.05, log2 fold change = 0.58), 250 genes were down-regulated and 411 up-regulated. There was a significant down-regulation of GAD1, GAD2 and HTR1A, HTR2A genes. CCK, PRKCG, mGluR4, and KCJN9 genes were significantly up-regulated. Some of these genes have been associated with anxiety and depression, while others have been shown to play a role in switching between tonic and burst firing modes in the thalamus and thus may be involved in gating of the respiratory stimuli. Furthermore, gene ontology and pathway analysis showed a significant modulation of learning and memory pathways. These results support the hypothesis that the medial thalamus is involved in the respiratory sensory neural pathway due to the state change of its gene expression profile following repeated tracheal occlusions.丘脑（thalamus）可能是参与感觉门控，并将呼吸机械信息传递至大脑皮层以实现呼吸意识感知的关键脑区。本研究假设，以气管阻塞为形式的呼吸机械刺激可调节丘脑的基因表达谱。具体而言，我们推测，对呼吸负荷的条件化训练可诱导内侧丘脑发生状态改变，这与感觉门控的变化以及学习记忆相关分子通路的激活相一致。此外，呼吸负荷具有应激性，因此应当会引发与应激、焦虑及抑郁相关的基因表达变化。实验大鼠被植入可充气气管袖带，待手术恢复后，大鼠接受为期10天（每周5天）的短暂气管阻塞条件化训练。于第10天时处死大鼠并取出脑组织，分离内侧丘脑并开展基因表达微阵列（microarray）分析。气管阻塞条件化训练共调控661个基因（p<0.05，log2倍变化=0.58），其中250个基因表达下调，411个基因表达上调。GAD1、GAD2、HTR1A及HTR2A基因的表达显著下调；CCK、PRKCG、mGluR4及KCJN9基因的表达显著上调。其中部分基因与焦虑及抑郁相关，另有部分基因被证实可参与丘脑紧张型与爆发型放电模式的切换，因此可能参与呼吸刺激的门控过程。此外，基因本体论（gene ontology）与通路分析显示，学习记忆通路发生了显著调控。上述结果支持本研究假设：在反复气管阻塞刺激后，内侧丘脑的基因表达谱发生状态改变，表明其参与呼吸感觉神经通路。