电针“太冲”改善两肾一夹型高血压大鼠的压力反射敏感性和孤束核α2肾上腺素受体活动

Electroacupuncture at “Taichong”(LR3) improves baroreflex sensitivity and α2-adrenergic receptor activity in nucleus tractus solitarii of hypertensive rats

目的:观察电针"太冲"对两肾一夹型高血压大鼠的动脉血压、交感神经活性、压力反射敏感性、孤束核(NTS)内α2肾上腺素受体(α2AR)的表达和功能的影响,探讨电针"太冲"降压效应的神经机制。方法:雄性SD大鼠随机分为假手术组、模型组、电针组和假电针组,每组12只。各组大鼠在植入遥测血压传感器探头后,采用两肾一夹法制备高血压大鼠模型。在模型建立4周后,各治疗组电针相应穴位,每日1次,持续28 d。用频域法评估自主神经功能,顺序法分析自发性压力反射敏感性,酶联免疫吸附法检测血浆去甲肾上腺素(NE)水平,免疫组织化学法检测NTS内α2AR阳性神经元变化,蛋白免疫印迹法检测NTS内α2AR表达水平,核团微注射法评价NTS内α2AR的功能变化。结果:与假手术组比较,模型组大鼠的平均动脉压、血浆NE含量及低频/总频谱(LF/TP)、低频/高频(LF/HF)值显著升高(P<0.01),压力反射总体增益、上行序列增益和下行序列增益显著降低(P<0.01),NTS内α2AR阳性神经元数量和蛋白表达水平显著下降(P<0.01),NTS内微注射可乐定诱发的平均动脉压和心率变化值显著缩小(P<0.01)。与模型组和假电针组比较,电针组大鼠的平均动脉压在电针治疗的第3、4周显著降低(P<0.01),血浆NE含量及LF/TP和LF/HF值均显著降低(P<0.01),压力反射总体增益、上行序列增益和下行序列增益显著升高(P<0.01),NTS内α2AR阳性神经元数量和蛋白表达水平显著升高(P<0.05),同时NTS内微注射可乐定诱发的平均动脉压和心率变化值也显著增大(P<0.05)。结论:电针"太冲"可以降低肾血管性高血压大鼠的动脉血压,抑制交感神经活性,改善压力反射敏感性,并上调NTS内的α2AR表达和功能活动。

Objective To investigate the effect of electroacupuncture(EA) at "Taichong"(LR3) on blood pressure, sympathetic nerve activity, baroreflex sensitivity, and α 2-adrenergic receptor(α2 AR) expression in nucleus tractus solitarii(NTS) in hypertensive rats, so as to reveal its mechanisms underlying improvement of hypertension. Methods Male Sprague Dawley rats were randomly divided into 4 groups: sham-operation, model, EA, and sham-EA(non-acupoint) groups, with 12 rats in each group. The hypertension model was established by occlusion of the right renal aorta(two-kidney-one clip method). Rats of the sham-operation group received the same surgery but without occlusion of the renal artery. EA(2 Hz/15 Hz, 2 mA) was applied to bilateral LR3 for 30 min, once a day for 28 days, and sham EA was applied to the skin of the rat tail near the buttock on both sides. The mean arterial pressure(MAP) of the abdominal aorta and heart rate(HR) were recorded. The autonomic nerve function was assessed by using frequency domain analysis of heart rate variability(HRV), and the baroreflex sensitivity detected by sequential method. Plasma norepinephrine(NE) level was measured by ELISA, and the α2 AR positive neurons and α2 AR protein expression in NTS were detected by using fluorescence immunohistochemistry and Western blot, respectively. The functions of α2 AR within the NTS in modulating MBP and HR were verified by microinjection of its agonist(clonidine) and antagonist(yohimbine) separately.Results Compared to the sham operation rats, the hypertension rats displayed significant increases in the MAP(P<0.01), plasma norepinephrine content(P<0.01), ratios of low frequency/total power(LF/TP) and low frequency/high frequency(LF/HF)(P<0.01), and significant reduction in the overall gain, uplink sequence gain and downlink sequence gain of baroreflex(P<0.01), the number α2 AR positive neurons and α2 AR protein expression level in NTS(P<0.01). The rats in the EA group(rather than in the sham-EA group) showed significant reduction in MAP at the 3 rd and 4 th week, plasma NE content, LF/TP and LF/HF(P<0.01), and obvious increase in the overall gain, uplink sequence gain and downlink sequence gain of baroreflex(P<0.01), and the number of α2 AR positive neurons and α2 AR protein expression in comparison(P<0.05) with those of the model group. Microinjection of clonidine into NTS induced an evident decrease in both MAP and HR in the model group relevant to the sham operation group(P<0.01), while the MAP and HR changes of the EA(not sham EA) group were considerably bigger than those of the model group(P<0.05), being similar to those of the sham-operation group(P>0.05), which suggested an elimination of the BP-lowering effect of clonidine after EA. Conclusion EA at LR3 can reduce MBP, sympathetic activities, improve baroreflex sensitivity in renovascular hypertensive rats, which may be associated with its effects in up-regulating the decreased NTS α2 AR expression and functional activities.