Noradrenergic mechanisms in breathing and respiratory pathophysiologies

项目摘要 这次更新的重点是扩大在目前的赠款开发的新发现，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，并确定NA功能障碍如何发挥作用 在两个威胁生命的病理生理学，雷特综合征和婴儿猝死综合征（SIDS）。Rett综合征 主要的女性神经发育障碍，表现为严重的呼吸紊乱， NA异常。SIDS是美国新生儿死亡的主要原因，每例死亡7-14名婴儿 并且与NA异常或与中央NA系统相互作用的其他回路有关。获得 为了进一步深入了解这些病理生理学中的NA机制，我们开发了几种交叉和交叉的机制 化学遗传神经回路映射工具，使我们能够细分NA系统到亚群定义 通过它们的发育起源在成年小鼠中进行功能评估。有了这些电路映射工具， 从我们实验室在呼吸测量技术的技术改进，我们发现，NA神经元， 来源于后脑菱形节3和5（胚胎模式的短暂遗传定义的片段）， r3，5）引起NA亚型，当化学发生沉默时，减少了 当化学发生刺激时，增强高碳酸盐反射。利用这些发现 和技术创新，我们已经在NA系统中启动了三个新的研究领域。1)有哪些 NA系统传出信号的分子机制，是重要的高碳酸反射？一 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r3，5 NA神经元中去除NA产生并不影响高碳酸反射，这表明另一种可能性。 递质，如共同表达的谷氨酸起作用或可以补偿。2)什么作用做菱形3，5 NA 神经元在呼吸紊乱中的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几乎不存在的高碳酸反射，表明这些神经元 仍然能够在疾病背景下驱动或调节化学感受功能。3)NA系统的作用是什么 在保护新生儿的自动复苏反射中起作用？新生儿自动复苏反射的失败被认为是 是许多SIDS病例的共同终点。我们假设NA化学发生刺激会增强 新生儿（P8）在SIDS样激发后自动复苏。然而，我们发现刺激导致了近50%的 死亡率增加，而NA系统抑制似乎使存活率提高50%。在拟议的工作中，我们力求 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、SIDS和Rett综合征。我们的工作成果将提供重要线索， 中央NA系统的发育遗传组织是其功能和机制整合的基础， 中枢呼吸网络以及该系统如何被破坏，从而在两种流行的 发育性呼吸系统疾病、Rett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.