Chemotransduction in the Carotid Body

描述（由申请人提供）：颈动脉体（CB）位于颈内动脉附近，是唯一检测动脉血中过少的O2（缺氧）或过多的CO2（高碳酸血症）或氢离子，并向大脑发出信号以产生几种呼吸和心血管反射反应的结构。本研究旨在进一步探讨脑脊液缺氧和高碳酸血症转导脑脊液神经输出量（CBNO）增加的机制。从普遍接受的器官结构和化学转导过程中的事件顺序出发，我们将解决三个问题：(a) CB乙酰胆碱（ACh）和CB多巴胺（DA）之间的关系是什么？(b)相关受体在哪里？(c)这些药物对CB球囊细胞（GC）的影响是什么？实验验证了从整体工作假设中得出的假设：乙酰胆碱是猫CBNO对缺氧和高碳酸血症反应的主要兴奋性神经制剂。猫表现出许多CB产生的反射反应，并作为CB神经生理反应特征的规范。据报道，一氧化氮（NO）、ATP和腺苷（ADO）对CBNO对缺氧和高碳酸血症的反应有影响，因此对乙酰胆碱的作用有影响。具体目的：(1)采用HPLC-ECD法测定体外缺氧/高碳酸血症诱导的过饱和烟叶中Ach、儿茶酚胺（catecholamines, CAs）和CBNO的释放，并测定NO、ATP和ADO对缺氧和高碳酸血症诱导的烟叶的影响；(2)应用RT-PCR和免疫细胞化学方法定位脑脊液、颈动脉窦神经和岩神经节（PG）细胞体中的多巴胺和嘌呤能受体；(3)采用膜片钳法测定DA、ATP和ADO对ach诱导的GCs膜电压和电流的影响，并采用微荧光法测定这些药物对[Ca2+]i的影响。患有几乎致命哮喘发作的患者已知具有低反应性CBs，而边缘性高血压患者具有高反应性CBs。睡眠过程中阻塞性呼吸暂停的减少取决于CB。通过更好地了解脑脊液的传导过程，可能通过基因操作或具有高度集中作用的药物，可以大大改善对这些情况的医疗管理。

DESCRIPTION (provided by applicant): The carotid body (CB), located near the internal carotid artery, is the only structure which detects too little O2 (hypoxia) or too much CO2 (hypercapnia) or hydrogen ion in the arterial blood, and signals the brain to produce several respiratory and cardiovascular reflex responses. This application proposes to explore further the mechanisms of CB's transduction of hypoxia and hypercapnia into increased the CB's neural output (CBNO). From a commonly accepted structure of the organ and sequence of events in the chemotransductive process we shall address three issues: (a) What is the relationship between CB acetylcholine (ACh) and CB dopamine (DA)? (b) Where are the pertinent receptors? (c) What is the impact of these agents back on the CB glomus cell (GC)? Experiments test hypotheses deriving from the overall working hypothesis: ACh is a (the) primary excitatory neuroagent for the CBNO's response to hypoxia and hypercapnia in the cat. The cat has exhibited many CB-generated reflex responses as well as serving as the norm for the CB's neurophysiological response characteristics. Nitric oxide (NO), ATP, and adenosine (ADO) are reported to have an effect on the CBNO's response to hypoxia and hypercapnia, and therefore on the role of ACh. SPECIFIC AIMS: (1) to measure the hypoxia-/hypercapnia- induced release of Ach and catecholamines (CAs) along with CBNO from the superfused CB in vitro with HPLC-ECD, and to measure the influence of NO, ATP, and ADO on the hypoxia- and hypercapnia-challenged CB; (2) to locate dopaminegic and purinergic receptors in the CB, the carotid sinus nerve, and in cell bodies of the petrosal ganglion (PG) with RT-PCR and immunocytochemistry; (3) to determine the effect of DA, ATP, and ADO on ACh-induced membrane voltages and currents of GCs with patch clamp, and the impact of these agents on [Ca2+]i with microfluorometry. Patients who have suffered near fatal asthma attacks are known to have hyporesponsive CBs, whereas borderline hypertensives have hyperresponsive CBs. Reduction of obstructive apneas during sleep depends on the CB. Medical management of these situations could be greatly improved with a better understanding of the CB's transductive processes, possibly with genetic manipulation or drugs with highly focused effects.