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

描述（由申请人提供）：细核和孤立束核（NTS）接受来自后肢的体感传入输入，在人和大鼠中，低频电针（EA）刺激后肢穴位ST36产生持久的交感神经抑制和动脉降压药。我们发现，在达尔盐敏感（DS）大鼠中，早期EA ST36（间隔80分钟、2小时以上的两个阶段）可以成功降低高血压，但短时间的EA不能显著降低高血压。DS大鼠细核和NTS区神经元一氧化氮合酶（nNOS）的表达明显降低，晚期EA ST36可恢复这些区域一氧化氮合酶的表达。与此一致的是，我们的初步结果表明，在DS大鼠纤细核中微量注射l -精氨酸可以促进EA ST36的抑制反应。微注射GABA受体拮抗剂或冠酰环化酶抑制剂可抑制NO供体对EA ST36降压反应的促进作用。我们假设纤细核和/或NTS中nNOS-NO生成受损导致DS大鼠高血压；先进EA ST36诱导脑核内nNOS-NO-GABA，通过中枢抑制调节心血管功能来控制高血压。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)研究高级EA ST36是否能改善盐负荷下DS大鼠的高血压，恢复细核和/或NTS中nNOS的表达；2)确定内源性NO-GABA在细核和mNTS中的释放是否诱导并平行于晚期EA ST36的心血管反应；3)确定细核和/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，以验证DS大鼠模型的假设。研究结果将有助于开发一种有效的高级治疗方法，以恢复纤细核/NTS中受损的nNOS，从而控制高血压，并为NO-cGMP-GABA在延髓背侧EA信号和心血管调节中的核心机制提供新的见解。

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.