CHEMOTRANSDUCTION IN THE CAROTID BODY

颈动脉体内的化学转导

• 批准号: 6389302
• 负责人: ROBERT Schaefer FITZGERALD
• 金额: $ 34.18万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 2003-09-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6389302
• 关键词: acetylcholine; anticholinergic agent; carotid body; cats; cholinergic agents; cranial nerves; dopamine; high performance liquid chromatography; hypercapnia; hypoxia; immunocytochemistry; membrane potentials; muscarinic receptor; nicotinic receptors; tissue /cell culture; voltage /patch clamp

DESCRIPTION (Adapted from the applicant's abstract): The broad long-term objectives of this proposal are to gain deeper insight into the mechanisms operating during the carotid body's (CB) chemotransduction of hypoxia, hypercapnia, and acidosis into increased neural activity recordable in the carotid sinus nerve. A commonly accepted model of the chemotransductive unit has an afferent nerve fiber of the glossopharyngeal nerve in a synaptic type contact with a Type I or glomus cell (GC) which contains neuroagents. When hypoxia depolarizes the GC, these neuroagents are released from the GC and apparently bind to receptors on the nerve fiber and GC. How and where these neuroagents act and precisely what receptors are involved in generating the increased neural activity is poorly understood. This application proposes to test the hypothesis that in the cat acetylcholine (ACh) is a principal excitatory neuroagent during hypoxia. Their recording of neural activity in the "postsynaptic" fibers suggests such a role for ACh during hypoxia. The applicant is proposing three major areas of research: (A) Measure the simultaneous release of ACh and dopamine (DA) from the cat CB during various physiological stimuli using the HPLC. The main question is to establish whether the amounts of ACh and DA released and their ratio during hypoxia differ from those values during hypercapnia. (B) They will determine the presence and location of nicotinic and muscarinic receptors in the CB and on fibers from the petrosal ganglion (PG) using immunocytochemical techniques and monoclonal antibodies. Their goal is to answer the question whether CB-directed fibers of the glossopharyngeal nerve contain nicotinic ACh receptors (nAChRs) of different alpha/beta subunit composition. (C) The third goal is to determine the impact of cholinergic agonists and antagonists on membrane potentials and currents in cultured cells and their impact on intracellular calcium. They will use biophysical (voltage clamping using patch-type electrodes to see if GCs or PG neurons produce the types of currents seen in hippocampal neurons dependent on the alpha/beta subunits of the nicotinic ACh receptors. In addition, they will use microfluorimetric techniques to determine changes in intracellular calcium. As for the clinical implications of this research the following is pertinent. Hyper responsive CBs are found in hypertensive young men, while hypo responsive CBs are found in asthmatics who have had near fatal attacks. Even more pertinent, congenital hypoventilation is associated strongly with Hirschsprung's Disease; the gene for this disease and the gene for choline acetyltransferase (synthesizes ACh) are both mapped to a common site, chromosome 10q.11.2.

描述(改编自申请人的摘要)：广泛的长期 这项建议的目的是更深入地了解这些机制 在低氧的颈动脉小体(CB)化学转导过程中进行操作， 高碳酸血症和酸中毒导致神经活动增加，可在 颈动脉窦神经。一种普遍接受的化学转导模型 单位在突触中有舌咽神经的传入神经纤维 与含有神经毒剂的I型或球状细胞(GC)进行类型接触。 当缺氧使GC去极化时，这些神经毒剂就会从GC中释放出来 明显地与神经纤维和GC上的受体结合。如何以及在哪里 这些神经毒剂的作用以及具体涉及哪些受体 人们对增加神经活动的产生知之甚少。这 应用程序建议测试假设，在猫乙酰胆碱 乙酰胆碱(ACh)是低氧时的主要兴奋性神经递质。他们的录音 突触后纤维中神经活动的研究表明ACh具有这样的作用 在缺氧期间。申请者提出了三个主要研究领域： (A)测量猫体内ACh和多巴胺(DA)的同时释放 CB在各种生理刺激下使用高效液相色谱仪。主要问题是 是确定ACh和DA的释放量及其比率 低氧时与高碳酸血症时不同。(B)他们会 确定烟碱受体和毒扁豆碱受体的存在和位置 岩神经节(PG)的CB和ON纤维 免疫细胞化学技术和单抗。他们的目标是 答：舌咽神经的CB纤维是否 含有不同α/β亚基的烟酸受体(NAChRs) 组成。(C)第三个目标是确定胆碱能 激动剂和拮抗剂对培养细胞膜电位和电流的影响 细胞及其对细胞内钙的影响。他们将使用生物物理 (使用贴片式电极进行电压钳制，看看GC或PG神经元 产生在海马神经元中所见的电流类型依赖于 烟碱型ACh受体的α/β亚基。此外，他们还将 使用显微荧光技术来确定细胞内的变化 钙。关于这项研究的临床意义，以下是 切合实际。高血压年轻男性中发现高反应性CBS，而 在哮喘患者中发现了低反应性CBS，他们的发作几乎是致命的。 更中肯的是，先天性低通气量与 先天性巨结肠症；该病的基因和胆碱基因 乙酰转移酶(合成ACh)都被映射到一个共同的位点， 染色体10q.11.2.