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

描述（申请人提供）：薄核和孤束核（NTS）接收来自后肢的体感传入输入，低频电针（EA）刺激后肢穴位ST36，对人和大鼠产生持久的交感神经抑制和动脉血压抑制作用。我们发现，在 Dahl 盐敏感 (DS) 大鼠中，先进的 EA ST36（2 小时内的两个阶段，间隔 80 分钟）成功降低了高血压，但 EA 在短刺激时间内没有显着降低高血压。 DS 大鼠的薄束核和 NTS 区域神经元一氧化氮 (NO) 合酶 (nNOS) 的表达主要减少，并且这些区域中减少的 nNOS 表达可通过高级 EA ST36 恢复。一致地，我们的初步结果表明，在 DS 大鼠的薄壁核中显微注射 L-精氨酸可促进对 EA ST36 的抑制反应。 NO 供体对 EA ST36 低血压反应的促进作用可通过将 GABA 受体拮抗剂或鸟苷酸环化酶抑制剂显微注射到纤细核中来抑制。我们假设，薄束核和/或 NTS 中 nNOS-NO 生成受损会导致 DS 大鼠高血压；先进的 EA ST36 在脑核中诱导 nNOS-NO-GABA，从而对心血管功能进行中枢抑制调节，从而控制高血压。鉴于NO对动脉血压调节的至关重要性，我们的主要目标是：1）检查高级EA ST36是否改善了盐负荷DS大鼠的高血压以及是否恢复了纤薄核和/或NTS中的nNOS表达； 2) 确定纤细核和 mNTS 中的内源性 NO-GABA 释放是否被诱导并与晚期 EA ST36 的心血管反应平行； 3) 确定薄核和/或 mNTS 中 L-精氨酸衍生的 NO 合成和 NO-cGMP-GABA 级联是否有助于高血压大鼠对晚期 EA ST36 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，以在 DS 大鼠模型中检验假设。研究结果应开发出一种有效的先进疗法，以恢复薄核/NTS 中受损的 nNOS，从而控制高血压，并为 NO-cGMP-GABA 对背髓质 EA 信号传导和心血管调节的中心机制提供新的见解。 公共健康相关性：这些研究应增进我们对背髓质中一氧化氮 (NO) 心血管调节作用的位点和机制的理解，并揭示 NO-GABA 在中央通路中电针 (EA) ST36 信号转导的新机制。研究结果将为公众健康提供针灸治疗机制，并基于在背髓质中诱导NO及其合酶的科学证据，建立临床治疗高血压和其他心血管疾病的金标准电针疗法。

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.