电针刺激足三里对内脏高敏感大鼠的影响及其机制

Effect and Mechanism of Electroacupuncture at ST-36 on Visceral Hypersensitivity in Rats

内脏高敏感是肠易激综合征（IBS）的重要发病机制之一，电针刺激足三里治疗IBS正逐渐应用于临床，然而其对内脏敏感性的影响及其作用机制尚不十分清楚。目的：研究电针刺激足三里对大鼠内脏感觉的影响以及近端结肠、远端结肠和丘脑组织中μ阿片受体蛋白表达的变化，以探讨μ阿片受体在电针治疗IBS中的作用。方法：32只Sprague-Dawlev大鼠随机分为正常对照组（NC组）、单纯模型组（M组）、模型＋电针组（MEA组）和模型＋假电针组（MSE组）。采用直肠灌注乙酸制备内脏高敏感模型。电针（假电针）治疗前后，大鼠行结直肠扩张后记录腹壁肌电。采用蛋白质印迹法检测各组大鼠近端结肠、远端结肠和丘脑组织中斗阿片受体的蛋白表达。结果：与电针刺激前相比，电针刺激后MEA组大鼠在相同结直肠扩张压力（20、40、60、80mmHg）下腹外斜肌放电次数均明显减少（P〈0．001）；而MSE组腹外斜肌放电次数无明显差异（P〉0．05）。与M组相比，MEA组近端结肠、远端结肠和丘脑组织中μ阿片受体蛋白表达明显增加（P〈0．05）．而MSE组无明显差异（P〉0．05）。结论：电针刺激足三里可降低大鼠内脏高敏感性，其作用机制可能通过上调中枢和外周μ阿片受体蛋白表达而实现的。

Background： Visceral hypersensitivity is one of the important pathological mechanisms of irritable bowel syndrome （IBS）, and electroacupuncture at ST-36 is gradually used in clinic for treating IBS. However, the effect and mechanism of electroacupuncture at ST-36 on visceral hypersensitivity is still unclear. Aims： To investigate the effect of electroacupuncture at ST-36 on visceral sensitivity and protein expression of mu opioid receptor in proximal colon, distal colon and thalamencephalon tissues in rats with visceral hypersensitivity, so as to study the role of mu opioid receptor in electroacupuncture therapy for IBS. Methods： Thirty-two Sprague-Dawley rats were randomly divided into four groups： normal control group （NC group）, model group （M group）, model ＋ electroacupuneture group （MEA group） and model ＋ sham electroacupuncture group （MSE group）. The visceral hypersensitivity model was established by perfusing acetic acid into rectum. The electromyogram in response to colorectal distension was recorded before and after electroacupuncture （or sham electroacupnncture）. The protein expression of mu opioid receptor in proximal colon, distal colon and thalamencephalon tissues was determined by Western blotting. Results： After electroacupuncture, the frequency of electrical activity of abdominal external oblique muscle responding to colorectal distension （20, 40, 60 and 80 mm Hg） in MEA group was significantly decreased （P〈0.001）, but no significant difference was found before and after sham electroacupuncture in MSE group （P〉0.05）. Compared with M group, the protein expression of mu opioid receptor in MEA group increased significantly in proximal colon, distal colon and thalamencephalon tissues （P〈0.05）, but no significant change was seen in MSE group （P〉 0.05）. Conclusions： Electroacupuncture at ST-36 attenuates visceral hypersensitivity in rats, and its mechanism may be via up-regulating the protein expression of central and peripheral mu opioid receptor.