慢性应激诱发高血压的神经机制研究

Chronic stress can switch borderline hypertension to persistent hypertension. However, the mechanisms are unclear. The increased excitability of corticotrophin-releasing hormone (CRH)-expressing neurons in hypothalamus and central nucleus of amygdala (CeA) are the main motive factor of stress reaction. Previous studies have shown that the depolarizing shift of the GABA reversal potential (EGABA) resulting from upregulation of the Na+-K+-2Cl- cotransporter-1 (NKCC1) causes a loss of GABAergic inhibition and subsequently increases excitability of CRH neurons. Our preliminary study has shown that chronic stress results in a persistent hypertension in borderline hypertension rats. Also, chronic stress induces an upregulation of the NKCC1 and a depolarizing shift of EGABA in CeA-CRH neurons. On the basis of these preliminary findings, we proposed a novel mechanism that upregulation of NKCC1 leads to over-activation of CeA-CRH neurons during chronic stress due to a depolarizing shift of EGABA. This over-activation of CeA CRH neurons switches borderline hypertension to persistent hypertension after chronic stress. In this proposal, we aim to investigate the central mechanism underlying chronic stress-induced switch of borderline hypertension to persistent hypertension by using a combination of multiple experimental techniques including telemetry monitoring blood pressue in free moving rat，brain microinjection，brain slice perforated patch clamp recording，viral vector-mediated transduction, molecular biology，and shRNA gene silencing techniques. This proposal will provide signficant insights into the central mechanisms involved in the chronic stress-induced hypertension. The findings from the proposed studies will be rational for the development of new treatment strategies to prevent the development of persistent hypertension from borderline hypertension. Also, these findings will have important theoretical and practical significance for the development of hypertension.

慢性应激可使临界高血压转变为持续性高血压，但其机制尚未明了。下丘脑及中央杏仁核(CeA)促肾上腺皮质激素释放激素(CRH)神经元兴奋性增高是应激反应的重要动因。阳离子氯化物协同转运体NKCC1上调可使GABA反转电位（EGABA）去极化漂移，GABA能抑制丧失，CRH神经元兴奋性升高。我们前期研究显示，慢性应激诱导临界高血压大鼠形成持续性高血压，同时CeA-CRH神经元NKCC1上调和EGABA去极化漂移。我们推测：慢性应激可上调NKCC1、使EGABA去极化漂移，CeA-CRH神经元过度兴奋，导致临界高血压转变为持续性高血压。本研究拟应用遥测、脑核微注射、脑片膜片钳、分生和shRNA基因沉默等方法，从整体、细胞和分子水平探讨慢性应激诱发持续性高血压的作用及其中枢机制。本研究将有助于深入理解慢性应激诱发高血压的中枢机制，发现防治高血压的新靶点，具有重要的理论意义和潜在应用价值。

慢性应激可使临界高血压转变为持续性高血压，但其机制尚未明了。下丘脑及中央杏仁核(CeA)促肾上腺皮质激素释放激素(CRH)神经元兴奋性增高是应激反应的重要动因。阳离子氯化物协同转运体NKCC1上调可使GABA反转电位（EGABA）去极化漂移，GABA能抑制丧失，CRH神经元兴奋性升高。我们前期研究显示，慢性应激诱导临界高血压大鼠形成持续性高血压，同时CeA-CRH神经元NKCC1上调和EGABA去极化漂移。我们推测：慢性应激可上调NKCC1、使EGABA去极化漂移，CeA-CRH神经元过度兴奋，导致临界高血压转变为持续性高血压。本研究应用遥测、脑核微注射、脑片膜片钳、分子生物学和shRNA基因沉默等方法探讨慢性应激诱发持续性高血压的作用及其中枢机制。. 结果显示：1.成功构建建了临界高血压大鼠模型。2.慢性应激可升高大鼠动脉血压，但临界高血压大鼠血压升高明显大于对照大鼠。慢性应激结束后，对照大鼠血压在2-3 天后恢复正常，而高血压大鼠血压在2-3 周后仍然保持在高血压水平。3.可准确可靠地标定大鼠CRH神经元。4.慢性应激高血压大鼠CeA 中NKCC1mRNA和蛋白表达水平较对照大鼠明显升高。5.CeA中NKCC1免疫反应性在PVN-CRH神经元中广泛表达。6.慢性应激可增强大鼠肾交感神经放电，但对应激高血压大鼠作用明显大于对照大鼠。7.应激高血压大鼠CeA-CRH神经元的放电活动较对照大鼠明显增强；GABA抑制对照大鼠CeA-CRH神经元放电，但增强高血压大鼠CeA-CRH神经元放电，并使GABA反转电位去极化漂移。8.NKCC1抑制剂可降低应激高血压大鼠CeA-CRH神经元放电活动，并阻止GABA反转电位的去极化漂移。9.应激高血压大鼠CeA-CRH神经元NMDA电流明显高于对照大鼠；阻断NMDA受体可阻止高血压大鼠CeA-CRH神经元GABA反转电位的去极化漂移。10.下调CeA中NKCC1表达可阻止应激诱导的持续高血压及交感神经传出的增强。. 以上结果表明，慢性应激可上调CeA中NKCC1表达和GABA反转电位的去极化漂移，使CeA-CRH神经元过度兴奋，导致临界高血压转变为持续性高血压。本研究有助于深入理解慢性应激诱发高血压的中枢机制，发现防治高血压的新靶点，具有重要的理论意义和潜在的应用价值。