Sympathetic Neurotransmitters and Ouabain Hypertension

交感神经递质和哇巴因高血压

• 批准号: 7312623
• 负责人: Withrow Gil Wier
• 金额: $ 35.81万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7312623
• 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.

瓦巴因引起的高血压的特点是交感神经系统亢进和血管平滑肌收缩增加。它也可能涉及小动脉交感神经肌肉传递的改变。本研究首先旨在确定小动脉交感神经递质释放的某些基本机制，然后确定乌巴因如何影响这些机制。本研究的基本前提是i)交感神经肌肉传递和动脉收缩主要涉及两种共递质，ATP和去甲肾上腺素（NE）， ii)这两种神经递质通过Ca2+依赖机制释放的差异尚未完全了解，可能涉及不同的突触囊泡，“残余[Ca2+]”和存储的Ca2+（除了Ca2+进入）。关于沃阿因作用机制的一个总体假设是，抑制神经末梢Na +泵会增加“残余”[ca2 +]和/或储存的ca2 +（从而增加NE和ATP的释放），末梢[ca2 +]的增加是由Na/Ca交换介导的。具体目的是：1)确定在个体交感神经曲张中ATP和NE释放的概率，2)测量ATP和NE传递包的大小（“量子”），3)验证NE和ATP的差异释放是由不同类型的突触囊泡释放引起的假设，4)验证急性低剂量瓦巴因抑制交感神经曲张中Na/ k -ATP酶的α 3亚型并改变概率的假设