Objective: To observe the effect difference of electroacupuncture (EA) at the sensitized and non-sensitized acupoint "Tianshu" (ST25) on the motility of jejunum in rats.
Methods: Male SD rats were randomly divided into blank control, sensitized ST25 (sensitization), and non-sensitized ST25 (non-sensitization) groups (n=16 in each group). The sensitization and non-sensitization were induced by injection of 15% mustard oil (20 μL) and Paraffin oil (20 μL) into the left ST25 area respectively. The rats' behavior reactions were assessed by recording the numbers and duration of licking the local sensitized skin region. At the end of experiments and after regular trans-cardiac perfusion and fixing with 10% neutral formaldehyde, the skin and muscular tissues of the ST25 region (1 cm×1 cm) were taken for H.E. staining to observe the local histopathologic changes. The intestinal motility was detected by recording the contraction pressure waves of jejunum through a small balloon-connected pressure transducer and an amplifier, followed by calculating the ratios of amplitude and frequency of contraction waves between pre- and post-EA stimulation. EA (2 Hz, 0.2-6.0 mA) was applied to the sensitized and non-sensitized ST25 regions for 20 s for comparing their effects on jejunum motility.
Results: Compared with the blank control group, mustard oil injection but not Paraffin oil injection resulted in histological edema and neutrophils infiltration in tissues of ST25 region, and also striking increase of the number and duration of licking (P<0.01), suggesting a sensitization of ST25 area after mustard oil injection. The ratios of spontaneous contraction amplitude and frequency of jejunum were remarkably decreased in mustard oil-treated rats compared to baseline and Paraffin oil group (P<0.001，P<0.01). The maximum inhibitory effect of EA on the intestinal movement amplitude was significantly higher in the sensitization group than in the blank control and non-sensitization groups (P<0.05，P<0.01), and there was a dose-effect relationship between the current intensity of EA (0.5-3.0 mA) and the inhibitory rate 50% of the contraction amplitude (not the frequency) in the sensitization group (P<0.001), but not in the blank control and non-sensitization groups (P>0.05). Additionally, 1.5 mA EA stimulation at the sensitized ST25 (not at the non-sensitized ST25) had an inhibitory effect on the contraction amplitude (P<0.05) rather than on the contraction frequency (P>0.05) in comparison with the blank control group.
Conclusion: Sensitization of acupoint ST25 can modulate the motility of jejunum and enhances the inhibitory effect of EA on the contraction amplitude of jejunum in rats. The inhibitory effect of sensitized ST25 EA is evidently stronger than that of the non-sensitized ST25 EA.
目的：观察电针敏化与非敏化“天枢”对大鼠空肠运动抑制效应的影响差异。方法：SD大鼠随机分为空白组、对照组、敏化组，每组16只，每组6只用于痛行为检测，每组10只用于肠运动记录。敏化组大鼠给予“天枢”局部注射15%芥子油溶液(20 μL)模拟穴位敏化，对照组注射石蜡油。以大鼠舔舐“天枢”的次数及时间为指标，观察“天枢”敏化时痛行为改变；HE染色观察芥子油引起“天枢”敏化的炎性改变；采用空肠内水囊置入法记录大鼠空肠运动收缩压力波，以波幅比值及频率比值为检测指标，观察“天枢”不同敏化状态对空肠自发运动及电针“天枢”抑制空肠运动效应的影响。结果：①与空白组及对照组比较，“天枢”注射芥子油引起局部组织充血水肿，且有大量中性粒细胞浸润，同时引起敏化组大鼠舔舐“天枢”的次数与时间显著增加(P<0.01)；②与基线及石蜡油比较，芥子油敏化“天枢”能够显著降低大鼠空肠运动的收缩压力波幅及频率比值(P<0.001，P<0.01)；与空白组及对照组比较，芥子油敏化“天枢”能够显著降低电针“天枢”产生抑制空肠运动所需的电流强度(P<0.05，P<0.01)，能增加1.5 mA电针刺激“天枢”对空肠运动波幅的抑制效应(P<0.05)，且量效关系分析三组50%抑制率对应的电针强度分别为：空白组为2.57 mA，对照组为2.42 mA，敏化组为1.25 mA。结论：“天枢”模拟敏化后，能够直接参与机体对空肠运动的调节，同时增强对电针刺激的响应性，放大电针“天枢”对空肠运动的抑制效应。.
Keywords: Acupoint sensitization; Dose-effect relationship; Electroacupuncture; Tianshu (ST25).