Chemotransduction in the Carotid Body

描述(申请人提供)：颈动脉小体(CB)位于颈内动脉附近，是唯一能检测到动脉血中氧气过少(缺氧)或二氧化碳(高二氧化碳)或氢离子过多的结构，并向大脑发出信号，使其产生几种呼吸和心血管反射反应。这一应用为进一步探讨CB通过低氧和高二氧化碳转导至增加CB的神经输出(CBNO)的机制提供了可能。根据普遍接受的器官结构和化学转导过程中的事件顺序，我们将解决三个问题：(A)CB乙酰胆碱(ACh)和CB多巴胺(DA)之间有什么关系？(B)有关的受体在哪里？(C)这些药物对CB球蛋白细胞(GC)有何影响？实验验证了源自整体工作假说的假设：ACh是猫CBNO对缺氧和高碳酸血症做出反应的主要兴奋性神经毒剂。猫已经表现出许多CB产生的反射反应，同时也是CB神经生理反应特征的标准。据报道，一氧化氮(NO)、三磷酸腺苷(ATP)和腺苷(ADO)对CBNO对低氧和高二氧化碳的反应有影响，因此对ACh的作用也有影响。具体目的：(1)用高效液相色谱-电子捕获检测法测定体外低氧/高碳酸血症诱导的脐血Ach、儿茶酚胺(CAs)和CBNO的释放，以及NO、ATP和ADO对缺氧/高碳酸血症诱导的CB的影响；(2)用RT-PCR和免疫细胞化学方法定位CB、颈动脉窦神经和岩神经节(PG)细胞体中的多巴胺能和嘌呤能受体；(3)用膜片钳技术观察DA、ATP和ADO对ACh诱导的GCs膜电压和电流的影响，并用微量荧光法测定其对[Ca~(2+)]i的影响。已知患有近乎致命的哮喘发作的患者患有低反应性CBS，而临界性高血压患者则患有高反应性CBS。睡眠中阻塞性呼吸暂停的减少取决于CB。如果更好地了解CB的转导过程，可能会通过基因操作或具有高度集中效应的药物，极大地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.