Study on efficacy specificity of electroacupuncture at "Zusanli "(ST36) and "Baihui" (GV20) in cerebral ischemia and inflammatory pain rats

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To explore the efficacy difference between electroacupuncture (EA) at "Zusanli" (ST36) and "Baihui" (GV20) for inflammatory pain and cerebral ischemia-reperfusion injury (CIRI) in rats. In 1st part of this study, 90 male SD rats were randomly divided into sham-operation, model (induced by occlusion of the middle cerebral artery and reperfusion), GV20 EA, ST36 EA，and sham EA groups (n=16 in each group). In the 2nd part of the study, 40 male SD rats were randomized into saline injection (control), inflammatory pain model (subcutaneous injection of complete Freund's adjuvant ［CFA］ into the right paw), ST36 EA, GV20 EA, and sham EA groups (n=8 in each group). In these two parts, EA (2 Hz/15 Hz, 1 mA) was applied to ST36 or GV20. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency （TWL） were detected 2.5 h after administration of CFA by using Von Frey and plantar tester, respectively. The neurological deficit scores (NDS) were assessed by using Longa's method and the infarct size of the brain assessed after staining with 2% triphenyltetrazolium chloride (TTC). The expression of c-fos protein in the dorsal horns (DHs) of the spinal cord was detected by immunohistochemistry. (1) Twenty-four hours following CIRI, the NDS and infarct volume were significantly increased in the model group compared with the sham-operation group (P<0.01), and obviously decreased in the GV20 EA and ST36 EA groups relevant to the CIRI model group (P<0.05, P<0.01). There were no significant differences between the two EA groups in the NDS and infarct volume levels (P>0.05). (2) After administration of CFA, both the MPT and TPT were notably decreased in the inflammatory pain model group in contrast to the saline-injection group (P<0.01), but were considerably increased in both ST36 EA and GV20 EA groups (P<0.05), rather than in the sham EA group (P>0.05). The number of c-fos positive cells was significantly increased in the medial half of I-II and III-IV lamina of DHs in the L4-L6 segments of spinal cord in the inflammatory pain model group relevant to the saline-injection group (P<0.01,P<0.05), and was remarkably decreased in the lamina I-II (not in the deeper lamina) in both ST36 EA and GV20 EA groups (P<0.01), rather than in the sham EA group (P>0.05). No significant differences were found in the number of c-fos positive cells between the ST36 EA and GV20 EA groups (P>0.05). Our data do not support the specificity of functions at least between GV20 EA and ST36 EA in both CIRI and inflammatory pain model rats. This is the first study reporting the effect of EA at GV20 for relieving CFA-induced inflammatory pain.