CHEMOTRANSDUCTION IN THE CAROTID BODY

颈动脉体内的化学转导

• 批准号: 2028960
• 负责人: ROBERT Schaefer FITZGERALD
• 金额: $ 30.96万
• 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 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2028960
• 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 本提案的目的是更深入地了解 在缺氧的颈动脉体（CB）化学转导期间操作， 高碳酸血症和酸中毒转化为神经活动增加， 颈动脉窦神经 一种普遍接受的化学转导模型， 单位具有突触中的舌咽神经的传入神经纤维 与含有神经毒剂的I型或血管球细胞（GC）接触。 当缺氧使GC去极化时，这些神经剂从GC中释放出来 并明显与神经纤维和GC上的受体结合。 如何以及在何处 这些神经因子的作用， 产生增加的神经活动的机制知之甚少。 这 应用程序提出测试的假设，在猫乙酰胆碱 (ACh)是缺氧时主要的兴奋性神经物质。 它们的记录 突触后纤维的神经活动表明ACh的这种作用 在缺氧的时候。 申请人提出了三个主要研究领域： (A)测量猫同时释放的ACh和多巴胺（DA） CB在各种生理刺激期间使用HPLC。 主体质询 是确定是否ACh和DA的释放量和它们的比例 与高碳酸血症期间的那些值不同。 (B)他们将 确定烟碱和毒蕈碱受体的存在和位置， CB和岩神经节（PG）的纤维， 免疫细胞化学技术和单克隆抗体。 他们的目标是 回答这个问题，是否CB定向纤维的舌咽神经， 含有不同α/β亚基的烟碱ACh受体（nAChR） 混合物. (C)第三个目标是确定胆碱能的影响， 激动剂和拮抗剂对培养的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学 （使用贴片型电极进行电压钳位，以观察GC或PG神经元 产生海马神经元中所见的电流类型， 烟碱ACh受体的α/β亚单位。 此外，他们将 使用显微荧光技术测定细胞内 钙 至于这项研究的临床意义， 中肯 高反应性CB见于高血压年轻男性， 低反应性CB存在于几乎致命的哮喘患者中。 更相关的是，先天性肺换气不足与 先天性巨结肠;这种疾病的基因和胆碱的基因 乙酰转移酶（合成乙酰胆碱）都定位在一个共同的位点， 染色体10q.11.2。