Noradrenergic mechanisms in breathing and respiratory pathophysiologies

项目总结摘要 这一更新的重点是扩展在当前拨款中开发的新发现，以描绘潜在的电路和 去甲肾上腺素能(NA)呼吸功能的分子机制以及NA功能障碍可能发挥的作用 在两种危及生命的病理生理学中，雷特综合征和婴儿猝死综合征(SID)。Rett综合征是 女性的主要神经发育障碍，表现为严重的呼吸紊乱，并与 有NA异常。小婴儿猝死综合征是美国新生儿死亡的主要原因，每个婴儿死亡7-14名 并与NA异常或与中央NA系统相互作用的其他电路有关。为了获得 对NA机制的更多了解在这些病理生理学中的每一个，我们已经发展了几个交叉和 化学发生神经回路映射工具，使我们能够将NA系统细分为定义的子种群 根据它们的发育来源在成年小鼠中进行功能评估。使用这些电路映射工具和 我们实验室在呼吸测量技术方面的技术改进，我们发现NA神经元 源自后脑菱形核3和5(瞬时的基因定义的片段，胚胎模式 后脑和由此产生的脑干；R3，5)产生NA亚型，当化学遗传学沉默时，减少 高碳酸血症反射，当化学刺激时，增强高碳酸血症反射。利用这些发现 在技术创新方面，我们在NA系统中启动了三个新的研究领域。1)什么是 NA系统传出信号的分子机制在高碳酸血症反射中起重要作用？一个 大量的R3，5神经元共表达神经递质谷氨酸。此外，初步数据显示 仅从R3，5NA神经元中去除NA的产生不会影响高碳酸血症反射，这表明另一种 递质、谷氨酸等共表达起到或可补偿的作用。2)菱形3，5 NA的作用是什么 神经元在雷特紊乱的呼吸中发挥作用。我们的初步数据表明，R3，5 NA的化学发生刺激 小鼠RETT模型中的神经元增强了原本几乎不存在的高碳酸血症反射，表明这些神经元 在疾病背景下仍然能够驱动或调节化学感觉功能。3)NA系统扮演什么角色 玩保护性新生儿自动复苏反射？新生儿自动复苏反射的失败被认为是 成为许多小岛屿发展中国家案例的共同终点。我们假设NA的化学生成刺激会增强 新生儿(P8)在类似小岛屿发展中国家的挑战后自动复苏。然而，我们发现刺激导致了近50%的 死亡率增加，而NA系统抑制似乎可以提高50%的存活率。在拟议的工作中，我们寻求 确定呼吸中关键NA亚群的分子和电路组织以及两个重要的 呼吸道病理生理学、小儿麻痹症和雷特综合征。我们的工作成果将提供重要的线索，说明如何 中央NA系统的发育遗传组织是其功能和机制整合为 以及这一系统如何被扰乱在两种流行的病因中发挥作用 发育性呼吸障碍、雷特综合征和致命的婴儿猝死综合征。

PROJECT SUMMARY ABSTRACT This renewal focuses on extending the novel findings developed in the current grant to delineate underlying circuit and molecular mechanisms in noradrenergic (NA) respiratory function and to determine how NA dysfunction may play a role in two life threatening pathophysiologies, Rett Syndrome and Sudden Infant Death Syndrome (SIDS). Rett Syndrome is the leading neuro-developmental disorder in females, presents with severe breathing perturbations, and is associated with NA abnormalities. SIDS is the leading cause of neonate mortality in the United States, claiming 7-14 infants each day and has been associated with NA abnormalities or other circuits that interact with the central NA system. To gain additional insight into NA mechanisms in each of these pathophysiologies, we have developed several intersectional and chemogenetic neural circuit mapping tools that have allowed us to subdivide the NA system into subpopulations defined by their developmental origin for functional assessment in the adult mouse. With these circuit mapping tools and technical enhancements from our laboratory in respiratory measurement techniques, we have found that NA neurons derived from hindbrain rhombomeres 3 and 5 (transient genetically defined segments that embryonically pattern the hindbrain and resulting brainstem; r3,5) give rise to NA sub-types that when chemogenetically silenced, reduce the hypercapnic reflex and when chemogenetically stimulated, enhance the hypercapnic reflex. Leveraging these findings and technical innovations, we have launched three novel areas of research in the NA system. 1) What are the molecular mechanisms in NA system efferent signaling that are important in the hypercapnic reflex? A significant number of r3,5 neurons co-express the neurotransmitter glutamate. Additionally, preliminary data indicates that removing NA production from only r3,5 NA neurons does not affect the hypercapnic reflex, suggesting another transmitter, such as co-expressed glutamate plays a role or can compensate. 2) What role do rhombomere 3,5 NA neurons play in Rett disordered breathing. Our preliminary data suggests that chemogenetic stimulation of r3,5 NA neurons in a mouse Rett model enhances an otherwise nearly absent hypercapnic reflex, indicating that these neurons are still able to drive or modulate chemosensory function in a disease background. 3) What role does the NA system play in the protective neonate auto-resuscitation reflex? Failure of the neonate auto-resuscitation reflex is thought to be a common endpoint for many SIDS cases. We hypothesized that NA chemogenetic stimulation would enhance neonate (P8) auto-resuscitation after a SIDS like challenge. However, we found that stimulation resulted in a near 50% increase in mortality while NA system inhibition appears to enhance survival by 50%. In the proposed work, we seek to determine the molecular and circuit organization of key NA subpopulations in breathing as well as two important respiratory pathophysiologies, SIDS and Rett Syndrome. The outcomes of our work will yield important clues as to how the developmental genetic organization of the central NA system underlies its functional and mechanistic integration into the central respiratory network and how this system may be disrupted to play a role in the etiology of two prevalent developmental respiratory disorders, Rett Syndrome and the fatal Sudden Infant Death Syndrome.