Project 3 HMS - VA sub

摘要 阻塞性睡眠呼吸暂停(OSA)的特征是由于睡眠关闭而频繁从睡眠中唤醒 上呼吸道，产生高碳酸血症(二氧化碳水平增加)和低氧(氧气减少 级别)。阻塞性睡眠呼吸暂停的后果包括白天过度嗜睡、认知缺陷以及 呼吸系统、代谢和心血管疾病。尽管它在阻塞性睡眠呼吸暂停综合征诱导的觉醒和 睡眠碎片，人们对阻塞性睡眠呼吸暂停时调节觉醒的神经机制知之甚少。 最近的研究表明，臂旁复合体(PB)的脑干谷氨酸能神经元 接受内脏和呼吸输入，对于高碳酸血症的唤醒很重要。我们假设PB 投射到基底前脑(BF)，这是一个包含皮质投射和觉醒促进的区域 神经元，调节皮层对高碳酸血症的唤醒反应。睡眠呼吸暂停将在小鼠身上建立模型 在睡眠期间暴露于高碳酸血症，称为重复性二氧化碳介导的觉醒(RCA)。 光遗传学技术将被用来研究神经递质定义的三个亚群的作用 在呼吸暂停诱发觉醒中皮质投射的BF神经元：GABA能小白蛋白阳性(PV)， 胆碱能和谷氨酸能神经元。对于每一种已识别的BF神经递质表型，我们将解决 标准：1)利用通道视紫红质2(ChR2)的光遗传兴奋的充分性；2)必要性 通过使用古紫红质(ARCHT)光遗传抑制RCA的觉醒；以及3)我们的 记录RCA相关BF电活动对自然生理条件的光遗传学研究 神经递质表型由ChR2的短潜伏期兴奋定义。每个人 当小鼠暴露在RCA或声刺激下时，将对神经元BF种群进行评估；我们预测两者都有 刺激将被唤醒，因为我们的数据表明，BF是最终的共同途径，从两者通向皮质唤醒 内脏和外部感官刺激。我们的初步数据表明，最常见的是PVGABe能神经元 对RCA和听觉觉醒的重要作用：1)BF PV神经元ChR2的兴奋引起觉醒和脑电 激活包括高频振荡；2)抑制PV ARCHT可显著延长RCA的潜伏期 觉醒；以及3)光伏单位记录显示激活与皮质激活一致。相比之下，ChR2 刺激BF胆碱能神经元表现出更强的调节性，更弱的威力和更少的即时效应 皮质激活程度高于PV神经元。我们预测谷氨酸能BF神经元将发挥促进作用 唤醒，但不是高频振荡。如果成功，这些实验将表明阻止BF 激活，特别是GABA能PV神经元的激活，会提高皮质觉醒阈值，从而 将治疗呼吸暂停症中明显的睡眠碎片，并对OSA的许多症状负责。 提高对阻塞性睡眠呼吸暂停患者皮质觉醒控制神经机制的理解将指导治疗 旨在减少皮质唤醒同时保持呼吸道通畅的治疗。

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.