Department of Neurobiology and Acupuncture Research, the Third School of Clinical Medicine, Zhejiang Chinese Medical University. Hangzhou 310053, Zhejiang,China
背景：疼痛是一种多维度的意识体验过程，包含感觉和消极的情感—动机两个组成部分。电针被广泛用于治疗疼痛和疼痛引起的负性情绪，但其作用机制尚不清楚。目的：本研究拟探讨电针对痛厌恶大鼠焦虑样行为的干预作用及其对前扣带回皮质（anterior cingulate cortex，ACC）的调节机制。方法：建立完全弗氏佐剂诱导条件性位置厌恶（Freund's complete adjuvant induced conditioned place aversion，C-CPA）的痛厌恶大鼠模型，对双侧“足三里”（ST36）和“昆仑”（BL60）穴进行电针治疗（2/100 Hz, 30 min，1次/天，共4天）。用Von Frey纤维在指定时间点测量大鼠的缩足阈值（paw withdrawal thresholds，PWTs）。采用高架O迷宫（elevated zero maze，EZM）观察大鼠焦虑相关的行为变化，采用条件性位置厌恶（conditioned place aversion，CPA）观察大鼠痛厌恶行为的变化。采用免疫印迹检测大鼠ACC中GAD67、PV、NPY蛋白表达水平。结果：与对照组比较，模型组大鼠在CFA配对腔室中的停留时间明显减少，并且其PWT阈值显著降低。在EZM实验中，模型组大鼠在开放臂的运动距离、运动时间、开放臂进入次数均显著低于对照组。在CPA实验中，与对照组相比，模型组在CFA配对腔室的停留时间明显减少，并且电针治疗能够扭转疼痛相关的情志变化。免疫印迹检测显示模型组ACC内NPY水平明显升高，而GAD67和PV水平未见明显升高，电针可显著下调ACC中NPY的表达。结论：电针能有效缓解疼痛及疼痛相关情绪，其机制可能是通过下调ACC内NPY的表达实现的。
Background: Pain is considered as a multidimensional conscious experience that includes a sensory component and a negative affective-motivational component. Electroacupuncture (EA) is widely used to treat pain and paininduced negative emotions, however, little is known about the mechanisms underlying the effect of EA. Objective: This study investigated the effect of EA on alleviating the anxiety-like behaviors in pain aversion rats and its anterior cingulate cortex (ACC) regulation mechanism. Methods: After a Freund’s complete adjuvant (CFA)-conditioned place aversion (C-CPA) model was established in rats, EA treatment (2/100 Hz, 30 min, once/day, 4 days totally) was applied at bilateral Zusanli (ST36) and Kunlun (BL60) acupoints. Von Frey filaments were used to measure changes of pain withdrawal threshold (PWT) at indicated time points. Elevated zero maze (EZM) was used to investigate the changes of pain-related anxiety and CPA was used to investigate the changes of pain aversion. The protein expression levels of GAD67, PV, and NPY in ACC were detected by Western blotting. Results: Compared with the control group, the staying time in the "CFA-paired compartment" was significantly reduced, and the PWT was decreased in model group. In the EZM assessment, the distance and the time in open arm, as well as the number of open arm entries of model group were significantly lower than those in the control group. In the CPA assessment, the time spent in the "CFA-paired compartment" was significantly decreased in model group compared with control group, and EA reversed the changes in pain sensation and in pain-related emotions. Western blotting showed that the NPY level, but not the levels of GAD67 and PV, was significantly increased in the ACC of the model group compared to that of the control group. The increased expression of NPY in the ACC was significantly downregulated by EA, while sham EA produced no such effect. Conclusion: EA can effectively relieve the pain and pain-related emotions, and its mechanism may be achieved by down-regulating the expression of NPY in the ACC.