Effects of Advanced EA on Hypertension: Role of nNOS-NO in the Dorsal Medulla

描述（由申请人提供）：薄束核和孤束核（NTS）接收来自后肢的躯体感觉传入输入，对人和大鼠的后肢穴位ST 36进行低频电针（EA）刺激可产生持久的交感神经抑制和动脉血抑制。我们已经发现，在Dahl盐敏感（DS）大鼠中，通过先进的EA ST 36（两个阶段超过2小时，间隔80分钟）成功地降低了高血压，但是通过具有短刺激期的EA没有显著降低。神经元型一氧化氮（NO）合酶（nNOS）的表达主要是减少在薄核和NTS地区在DS大鼠，和减少nNOS表达的地区是由先进的EA ST恢复36。因此，我们的初步结果表明，在DS大鼠薄束核内微量注射L-精氨酸可使EA ST 36的降压反应变得易化。薄核内注射GABA受体拮抗剂或鸟苷酸环化酶抑制剂均能抑制NO供体对EA ST 36诱发的兴奋反应的促进作用。我们推测，受损的nNOS-NO在薄核和/或NTS的产生导致高血压在DS大鼠;先进的EA ST 36诱导nNOS-NO-GABA在脑核团，导致中枢抑制性调节心血管功能的高血压控制。鉴于NO在动脉血压调节中的重要作用，我们的主要目的是：1）观察电针是否能改善盐负荷的DS大鼠的高血压，恢复薄核和（或）孤束核（NTS）中nNOS的表达; 2）观察电针是否能诱导薄核和mNTS中内源性NO-GABA的释放，并对电针的心血管反应产生影响;（3）确定高血压大鼠薄核和/或mNTS中L-精氨酸来源的NO合成和NO-cGMP-GABA级联反应是否参与了晚期EA ST 36的心血管反应。动脉血压和心率的生理记录将与神经药理学操作、分子检查和组织化学研究相结合，以检验DS大鼠模型中的假设。这些结果将为恢复薄束核/NTS受损的nNOS以控制高血压提供有效的先进治疗方法，并为NO-cGMP-GABA对背侧延髓EA信号和心血管调节的中枢机制提供新的见解。 公共卫生相关性：这些研究将进一步加深我们对一氧化氮（NO）在延髓背侧参与心血管调节的部位和机制的认识，并揭示NO-GABA在电针ST 36中枢信号转导中的新机制。本研究结果为针灸治疗高血压等心血管疾病提供了一种新的机制，并为临床上电针治疗高血压等心血管疾病提供了一个金标准。

DESCRIPTION (provided by applicant): The gracile nucleus and nucleus tractus solitarius (NTS) receive somatosensory afferent inputs from the hindlimb, and low-frequency electroacupuncture (EA) stimulation of hindlimb acupoint ST36 produces long-lasting sympathoinhibition and arterial blood depressor in humans and rats. We have found that hypertension is successfully reduced by advanced EA ST36 (two phases over 2 hrs separated by an 80 min interval) in Dahl salt- sensitive (DS) rats but not significantly decreased by EA with a short stimulation period. Expression of neuronal nitric oxide (NO) synthase (nNOS) is predominantly reduced in the gracile nucleus and NTS regions in DS rats, and decreased nNOS expression in the areas is restored by advanced EA ST36. Consistently, our preliminary results show that the depressor responses to EA ST36 are facilitated by microinjection of L-arginine in the gracile nucleus in DS rats. The facilitating effects of NO donors on the hypotensive responses to EA ST36 are inhibited by microinjection of either an antagonist of GABA receptors or an ihhibitor of guanylyl cyclase into gracile nucleus. We hypothesize that impaired nNOS-NO generation in the gracile nucleus and/or NTS causes hypertension in DS rat; advanced EA ST36 induces nNOS-NO-GABA in the brain nuclei, resulting in central inhibitory regulation of cardiovascular functions for hypertension control. In view of the critical importance of NO on arterial blood pressure regulation, our major aims are: 1) Examine whether hypertension in DS rats with salt load is improved and nNOS expressions in the gracile nucleus and/or NTS are restored by advanced EA ST36; 2) Determine whether endogenous NO-GABA releases in the gracile nucleus and mNTS are induced and paralleled to cardiovascular responses to advanced EA ST36; 3) Define whether L-arginine-derived NO synthesis and NO-cGMP-GABA cascade in the gracile nucleus and/or mNTS contribute to cardiovascular responses to advanced EA ST36 in hypertensive rats. The physiological recordings of arterial blood pressure and heart rate will be incorporated with neuropharmacological manipulations, molecular examinations and histochemical studies to test the hypotheses in a DS rat model. The results should develop an effective advanced therapy to restore impaired nNOS in the gracile nucleus/NTS for hypertension control and yield new insights into central mechanisms of NO-cGMP-GABA on EA signaling and cardiovascular regulation in the dorsal medulla. PUBLIC HEALTH RELEVANCE: These studies should advance our understanding of sites and mechanisms of nitric oxide (NO) in the dorsal medulla for cardiovascular regulation and reveal a novel mechanism of NO-GABA for signal transduction of electroacupuncture (EA) ST36 in the central pathways. The results should benefit public health by providing a theraputic mechanism of acupuncture, and establish a gold-standard EA therapy based on scientific evidence of inducing NO and its synthase in the dorsal medulla for clinical treatment of hypertension and other cardiovascular diseases.