Project 3 HMS - VA sub

摘要 阻塞性睡眠呼吸暂停（OSA）的特征是由于呼吸道的关闭而频繁地从睡眠中唤醒。 上呼吸道，产生高碳酸血症（二氧化碳水平增加）和缺氧（氧气减少 水平）。OSA的后果包括白天过度嗜睡，认知缺陷，以及 呼吸、代谢和心血管疾病。尽管它在阻塞性睡眠呼吸暂停引起的觉醒和 睡眠片段，很少有人知道的神经机制，介导觉醒在阻塞性睡眠呼吸暂停综合征。 最近的工作表明，脑干的臂旁复合体（PB）， 接收内脏和呼吸输入，对于高碳酸血症觉醒是重要的。我们假设PB 投射到基底前脑（BF），一个包含皮质投射和觉醒促进的区域 神经元介导对高碳酸血症的皮质唤醒反应。睡眠呼吸暂停将在小鼠中建模， 在睡眠期间暴露于高碳酸血症，称为重复二氧化碳介导的觉醒（RCA）。 光遗传学技术将被用来研究三个神经递质定义的亚群的作用 皮质投射BF神经元在呼吸暂停诱导觉醒中的表达：GABA能小清蛋白阳性（PV）， 胆碱能和多巴胺能神经元。对于每一个确定的BF神经递质表型，我们将解决 标准：1）使用视紫红质2（ChR 2）通过光遗传学激发的唤醒的充分性; 2）必要性 对于通过使用古视紫红质（ArchT）的RCA的光遗传学抑制的唤醒;以及3）我们的研究的相关性。 通过记录RCA相关BF的电活动， 神经元，其神经递质表型已通过ChR 2的短潜伏期兴奋来定义。每个 当小鼠暴露于RCA或声刺激时，将评估神经元BF群体;我们预测两者都是 刺激将引起，因为我们的数据表明BF是导致两种刺激的皮层唤醒的最终共同途径。 内脏和外部感官刺激。我们的初步数据表明PV GABA能神经元是最重要的神经元。 对于RCA和声学唤醒重要的是：1）BF PV神经元的ChR 2兴奋引起唤醒和EEG 2）PV ArchT抑制显著延长RCA潜伏期 唤醒;和3）PV单位记录显示与皮层激活一致的激活。相反，ChR 2 BF胆碱能神经元的刺激显示出更多的调节，更少的力量和更少的直接影响， 皮质激活比PV神经元。我们预测，多巴胺能BF神经元将发挥促进作用， 唤醒，但不是高频振荡。如果成功的话，这些实验将表明， 激活，特别是来自GABA能PV神经元的激活，会增加皮层唤醒阈值， 将治疗呼吸暂停中明显的睡眠碎片，并导致许多阻塞性睡眠呼吸暂停综合症的症状。 对控制OSA皮层觉醒的神经机制的进一步理解将指导治疗 治疗旨在减少皮质觉醒，同时保持气道通畅。

ABSTRACT Obstructive sleep apnea (OSA) is characterized by frequent arousals from sleep due to closure of the upper airway, producing hypercapnia (increased carbon dioxide levels) and hypoxia (decreased oxygen levels). The consequences of OSA include excessive daytime sleepiness, cognitive deficits, as well as respiratory, metabolic, and cardiovascular disorders. Despite its importance in OSA-induced arousals and sleep fragmentation, very little is known about the neural mechanisms that mediate arousals during OSA. Recent work indicates that the brainstem glutamatergic neurons of the parabrachial complex (PB), which receive visceral and respiratory input, are important for hypercapnic arousal. We hypothesize that the PB projections to the basal forebrain (BF), a region containing cortically projecting & wakefulness promoting neurons, mediate the cortical arousal response to the hypercapnia. Sleep apnea will be modeled in mice by exposure to hypercapnia during sleep, termed repetitive carbon dioxide-mediated arousals (RCA). Optogenetic techniques will be used to investigate the roles of three neurotransmitter-defined subpopulations of cortically-projecting BF neurons in apnea-induced arousals: GABAergic parvalbumin positive (PV), cholinergic, and glutamatergic neurons. For each identified BF neurotransmitter phenotype we will address the criteria of: 1) sufficiency for arousal by optogenetic excitation using Channelrhodopsin 2 (ChR2); 2) necessity for arousal by optogenetic inhibition of RCA using Archaerhodopsin (ArchT); and 3) relevance of our optogenetic findings to natural physiological conditions by recording the electrical activity of RCA -related BF neurons whose neurotransmitter phenotype has been defined by short latency excitation by ChR2. Each neuronal BF population will be evaluated as mice are exposed to RCA or acoustic stimuli; we predict both stimuli will arouse, as our data point to the BF as a final common pathway leading to cortical arousal from both visceral and external sensory stimuli. Our preliminary data point to PV GABergic neurons as the most important for RCA and acoustic arousals: 1) ChR2 excitation of BF PV neurons causes arousal and EEG activation including high frequency oscillations; 2) PV ArchT inhibition markedly prolongs the latency to RCA arousal; and 3) PV unit recordings show activation in concert with cortical activation. In contrast, ChR2 stimulation of BF cholinergic neurons shows more modulatory, less powerful and less immediate effects on cortical activation than PV neurons. We predict that glutamatergic BF neurons will play a role in promoting arousal, but not high frequency oscillations. If successful, these experiments would suggest that blocking BF activation, especially that from GABAergic PV neurons, would increase the cortical arousal threshold, and thus would treat the sleep fragmentation evident in apnea and responsible for many of the symptoms of OSA. Improved understanding of the neural mechanisms controlling cortical arousals in OSA will guide therapeutic treatment aiming to decrease cortical arousals while maintaining airway patency.