Sympathetic Neurotransmitters and Ouabain Hypertension

交感神经递质和哇巴因高血压

• 批准号: 6968175
• 负责人: Withrow Gil Wier
• 金额: $ 34.76万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-12-01 至 2009-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6968175
• 关键词: adenosine triphosphate; calcium flux; calcium indicator; clinical research; essential hypertension; genetically modified animals; laboratory mouse; laboratory rat; microelectrodes; muscle contraction; neuromuscular transmission; neuropharmacology; neuroregulation; neurotransmitter transport; norepinephrine; ouabain; protein isoforms; sodium ion; sodium potassium exchanging ATPase; sympathetic nervous system; synaptic vesicles; vascular smooth muscle; vascular smooth muscle nervous control

Ouabain-induced hypertension is characterized by hyperactivity of the sympathetic nervous system and increased contraction of vascular smooth muscle. It may also involve changes in sympathetic neuromuscular transmission in small arteries. The proposed research aims first to determine certain basic mechanisms of sympathetic transmitter release in small arteries, and then, to determine how these are affected by ouabain. Basic premises of the research are i) that sympathetic neuromuscular transmission and arterial contraction importantly involve the two co-transmitters, ATP and nor-epinephrine (NE) and, ii) that these two neurotransmitters are differentially released by Ca 2+ dependent mechanisms that are not yet completely known, possibly involving different synaptic vesicles, 'residual [Ca2+] ' and stored Ca 2+ (in addition to Ca 2+ entry). An overall hypothesis on mechanisms of ouabain actions is that inhibition of nerve terminal Na + pumps increases 'residual' [Ca 2+] and/or stored Ca 2+(thereby increasing NE and ATP release) and that the increases in terminal [Ca 2+] are mediated by Na/Ca exchange. Specific Aims are: 1) Determine the probabilities, at individual sympathetic nerve varicosities, of ATP and NE release, 2) Measure the sizes of ATP and NE transmitter packets ('quanta'), 3) Test the hypothesis that differential release of NE and ATP results from the release of different types of synaptic vesicles, 4) Test the hypothesis that acute, low-dose, ouabain inhibits the alpha3-isoform of the Na/K-ATPase in sympathetic varicosities and changes the probability of release, but not quantal size, 5) Determine whether release probability or quantal size is altered in ouabain hypertensive rats. Rat and mouse mesenteric small arteries will be loaded with fluorescent Ca 2+ indicators and studied in a myograph that permits simultaneous confocal fluorescence imaging, electrical stimulation/recording, and recording of isometric force development. Mice with genetically altered Na/Ca exchangers or ATP receptors will be used. Junctional Ca 2+ transients (jCaTs) will be used to measure neurally released ATP. Carbon fiber microelectrodes and amperometry will be used to measure NE release as 'NE oxidation currents' (NEOCs). The research will measure NE and ATP release together for the first time and thereby determine some of the basic mechanisms that control neurogenic contractions of arteries. will elucidate the mechanisms by which sympathetic nerves contribute to ouabain-induced hypertension.

哇巴因诱发的高血压的特征是交感神经系统过度活跃和血管平滑肌收缩增加。它还可能涉及小动脉中交感神经肌肉传递的变化。拟议的研究旨在首先确定小动脉中交感神经递质释放的某些基本机制，然后确定哇巴因如何影响这些机制。该研究的基本前提是 i) 交感神经肌肉传递和动脉收缩重要地涉及两种共同递质 ATP 和去甲肾上腺素 (NE)，以及 ii) 这两种神经递质通过 Ca 2+ 依赖性机制差异释放，该机制尚未完全了解，可能涉及不同的突触小泡、“残留 [Ca2+]”和储存的 Ca 2+（除了 Ca 2+ 条目）。关于哇巴因作用机制的总体假设是，抑制神经末梢 Na + 泵会增加“残留”[Ca 2+] 和/或储存的 Ca 2+（从而增加 NE 和 ATP 释放），并且末端 [Ca 2+] 的增加是由 Na/Ca 交换介导的。具体目标是：1) 确定个体交感神经静脉曲张处 ATP 和 NE 释放的概率，2) 测量 ATP 和 NE 递质包（“量子”）的大小，3) 检验 NE 和 ATP 的差异释放是由不同类型的突触小泡的释放导致的差异这一假设，4) 检验急性、低剂量哇巴因抑制 α3-亚型的假设的 交感静脉曲张中的 Na/K-ATP 酶并改变概率 5) 确定哇巴因高血压大鼠的释放概率或量子大小是否改变。大鼠和小鼠肠系膜小动脉将装载荧光 Ca 2+ 指示剂，并在肌动描记器中进行研究，该肌动描记器允许同时进行共焦荧光成像、电刺激/记录以及记录等长力发展。将使用具有基因改变的 Na/Ca 交换器或 ATP 受体的小鼠。连接 Ca 2+ 瞬变 (jCaTs) 将用于测量神经释放的 ATP。碳纤维微电极和电流分析法将用于测量 NE 释放，即“NE 氧化电流”(NEOC)。该研究将首次同时测量 NE 和 ATP 的释放，从而确定控制动脉神经源性收缩的一些基本机制。 将阐明交感神经导致哇巴因诱发高血压的机制。