| Electroacupuncture Analgesia on Experimental Dysmenorrhea Model Rat and Its MechanismThe theory of acupuncture considers that stimulating acupoints can regulate the functions of the corresponding viscera specifically, of which is different comparing to the functions regulated by stimulating non-acupoint or acupoints on other meridians. This difference is specificity of the acupoint effect, which is the core content of the meridian theory and an important basis of locating acupoints along meridian in clinical. A large amount of clinical research and experimental study have confirmed the existence of specificity.The research results of modern neuroscience on acupuncture mechanism also showed the existence of specificity of acupoint effect, which was mainly caused by different nerve segments innervating acupoint area. And it was mostly related to the locations of acupoints but had nothing to do with the meridians. That meant there was no difference found among acupoint effect of different meridians innervated by the same nerve segment or difference between acupoints on the same meridian and non acupoints. And what is specificity of acupoint effect in the end? Is there effect specificity among the different meridian acupoints and non-acupoint innervated by the same nerve segment? How about the effect of different acupoints on the same meridian?The aim of the present study was to explore whether the specificity of acupoint effects exists and has certain principles or not by comparing the effect and possible mechanism of electroacupuncture analgesia on experimental dysmenorrhea model rat at different acupoints innervated by the same nerve segment.Selected acupoints for the experiment were as follows:Sanyinjiao(SP 6), Xuehai(SP 10) on the Spleen meridian of Foot Taiyin as relevant acupoints; Xuanzhong(GB 39) on Gallbladder Meridian of Foot Shaoyang as non-relevant acupoints; and non-acupoints located in the middle acupoint between the gallbladder meridian and the stomach meridian at the horizontal line of Xuanzhong(GB 39). The experiments used 156 female Sprague-Dawley (SD) rats which were during their diestrus. SD rats were randomly divided into 6 groups, which included saline control group, model control group, EA Sanyinjiao group, EA Xuehai group, EA Xuanzhong group, EA non-acupoint group, and 26 rats in each group. Except the saline control group, the rest of groups were injected estradiol benzoate for 10 days, the first and 10th day 0.5 mg for each, and from 2th to 9th days 0.2mg for each.1 hour after the last injection, Oxytocin was given to each by intraperitoneal injection with 2u. The saline control group was given for the same dose of saline everyday. According to the standard of Schmauss behavior score, we recorded latency of writhing, writhing times and writhing score in 20 minutes; applied BL-420E+logger of experimental system to record times and intensity of uterine contraction in 20 minutes; used radio immunoassay to detect the content of PGE2, PGF2a in uterine; observed expression ofκ-opioid receptor in the dorsal horn of the spinal cord by immunohistochemical staining; and detected ENK, B-EP, Dyn, EM content in the periaqueductal gray (PAG) of midbrain by ELISA. The results were as follows:1 Effect of Electroacupuncture at different acupoints on writhing response in ratsCompared to the saline control group, latency of writhing, writhing times and writhing score of model control group significantly changed (P<0.01), that meant the model was successfully prepared.All the EA groups comparing to the model control group:writhing latency of EA Sanyinjiao group was significantly prolonged (p<0.05), writhing latency of the other groups was also prolonged, but there was no statistical difference (p>0.05); writhing score and writhing times decreased significantly in each group.(p<0.01).but the writhing score of Sanyinjiao group had no statistical difference comparing to the saline control group (p>0.05).The results above showed that:After electro-acupuncture treatment on different acupoints, the writhing response of experimental dysmenorrheal model in rats could be relieved at different degrees. There was the best effect in EA Sanyinjiao group, and the differences were not significant among EA Xuehai group, EA Xuanzhong group and EAnon acupoint group.2 Effect of electroacupuncture on different acupoints about the uterine contraction of ratsModel control group comparing to the saline control group:the time and intensity of uterine contraction significantly increased (p<0.01) which meant the smooth muscle of uterus was induced spasmodic contraction.the model was successfully prepared.All the EA groups comparing to model control group:time of uterine contractions were reduced significantly in Sanyinjiao group and Xuehai group (p <0.05); and the intensity of uterine contraction in Sanyinjiao group had a better effect than other groups (p<0.05).All the EA groups comparing to the saline control group, intensity of uterine contraction hadn't a significant difference in other groups except non-acupoint group (p>0.05).The results above showed that:acupuncture could improve spasmodic contraction of uterus of experimental dysmenorrhea rat to alleviate pain in the uterus. As a conclusion, the EA Sanyinjiao group had the best effect than others, Xuehai group and Xuanzhong group also had a certain effect, with a better effect in Xuehai group. The effect of non-acupoint hadn't significantly changed.3 Effect of electroacupuncture on different acupoints on the content of PGE2, PGF2a and the content ratio of PGE2/PGF2a in the rat uterusModel control group comparing to the saline control group:the content of PGF2a significantly increased, and the content of PGE2 decreased significantly. The both ratio increased significantly (p<0.01); which implied that the content of pain-producing substance in uterine tissue increased after modeling.All the EA groups comparing to model control group:PGF2a content decreased significantly (Sanyinjiao group:p<0.05; the other groups:p<0.01); PGE2 content in Sanyinjiao group increased more significantly than other groups (p<0.01); and the ratio of PGE2/PGF2a in EA groups significantly decreased (p< 0.01).All the EA groups comparing to the saline control group:PGE2 content of all groups except Sanyinjiao group significantly decreased (Xuehai group:p<0.05; the other groups:p<0.01); the ratio of PGE2/PGF2a between Sanyinjiao group and Xuanzhong group showed no statistical differences (p>0.05)PGE2 content in Sanyinjiao group were significantly increased than the other groups (p<0.01).The results above indicated that:Acupuncture could regulate the content of pain-producing substance in uterus tissue of experimental dysmenorrhea rat to relieve pain. According to the comprehensive effect, Sanyinjiao group achieved best effect than the other groups.4 Effect of electroacupuncture on different acupoints on expression of theκ-opioid receptor in dorsal horn of spinal cord of different segments of rat spinal cordDifferent acupoints and non-acupoint have different effects on the expression ofκ-receptor in the spinal cord segments. T13 segment:Model control group comparing to the saline control group:The integral optical density (IOD) of the K-receptors positive expression increased, but had no statistical differences (P>0.05).All the EA groups comparing to model control group:the IOD in Sanyinjiao group and Xuehai group both increased significantly (P<0.01); the IOD in Xuanzhong group and non-acupoint group increased, but had no statistical differences (P>0.05).The acupoint groups comparing to non-acupoint group:the IOD in Sanyinjiao group and Xuehai group both increased significantly (P<0.01); the IOD in Xuanzhong group hadn't showed any statistical differences (P>0.05). L1 segment:Model control group comparing to the saline control group:the IOD increased, and the difference was not significant (P> 0.05).All the EA groups comparing to model control group:the IOD in Sanyinjiao group andXuehai group both increased significantly (P<0.01); the IOD in Xuanzhong group and non-acupoint group also increased, but had no statistical differences (P>0.05).Comparing to non-acupoint group and Xuanzhong group, the IOD in Sanyinjiao group andXuehai group significantly increased (P<0.01). L2 segment:Model control group comparing to the saline control group:the IOD significantly increased, and had statistical difference(P<0.01).All the EA groups comparing to model control group:the IOD in Sanyinjiao group and Xuehai group both increased significantly (P<0.01); the IOD in Xuanzhong group and non-acupoint group also increased, but had no statistical differences (P>0.05).Comparing to Xuehai group, Xuanzhong group non-acupoint group, the IOD in Sanyinjiao group significantly increased (P<0.01). L6 segment:Model control group comparing to the saline control group:the IOD increased, and the difference was not significant (P>0.05).All the EA groups comparing to model control group:the IOD in Sanyinjiao group, Xuehai group and non-acupoint group increased obviously (P<0.01); the IOD in Xuanzhong group also increased, but had no statistical differences (P>0.05).Comparing to non-acupoint group:the IOD in Sanyinjiao group significantly increased (P<0.01).there were more significant statistical differences in increasing of the IOD in Sanyinjiao group and Xuehai group than that in Xuanzhong group (P <0 .01). S1 segment:Model control group comparing to the saline control group:the IOD increased, and the difference was not significant (P>0.05).All the EA groups comparing to model control group:the IOD in Sanyinjiao group, Xuehai group and Xuanzhong group increased obviously (Sanyinjiao:P<0.01, Xuehai group, Xuanzhong group:P<0.05); the IOD in non-acupoint group had no statistical differences (P>0.05). Comparing to Xuehai group and non-acupoint group, the IOD in Sanyinjiao group significantly increased (P<0.01).Comparison among the acupoint groups, the IOD in Sanyinjiao group increased more significantly than that in Xuehai group (P<0.05).These results show that:EA can adjust K-receptor expression of dorsal horn of spinal cord in all segments, but different acupoints have different effect on the different segments. Sanyinjiao group and Xuehai group can regulate all the segments, and Sanyinjiao group has a better effect; Xuanzhong group and non-acupoint group just have a certain obvious effect in individual segment, and there are no significant differences among Xuanzhong group and non-acupoint group.5 Effect of electroacupuncture on different acupoints on endopioid peptide in PAG5.1 Effect of electroacupuncture on different acupoint on ENK content in PAG:Model control group comparing to the saline control group:ENK content in PAG increased, but had no statistical differences (P>0.05), which meant that in the rat model of experimental dysmenorrhea, the ENK content in PAG didn't increase significantly.All the EA groups comparing to model control group:the ENK content in Sanyinjian group and Xuanzhong group significantly increased (Sanyinjiao group:P <0.01; Xuanzhong group:P<0.05); but there were no significant differences in increasing of ENK content between Xuehai group and non-acupoint group (P>0.Q5).Comparing to the Xuanzhong group, Xuehai group and non-acupoint group, the ENK content in Sanyinjian group significantly increased, (Xuehai and non-acupoint group:P<0.01, Xuanzhong group:P<0.05); there were no significant differences on increasing of ENK content between Xuehai group and Xuanzhong group (P>0.05).These results suggest that:Acupuncture could regulate the levels of ENK in PAG of rats with different effects. Sanyinjiao group and Xuanzhong group could significantly adjust ENK content in PAG, and Sanyinjiao group had a better effect. And the Xuehai group and non-acupoint group had no significant changes. 5.2 Effect of electro-acupuncture on different acupoints on B-EP content in the PAG:Model control group comparing to the saline control group:the B-EP content in PAG increased, but had no statistical differences (P>0.05), which meant that the B-EP content in PAG didn't increase significantly in the rat model of experimental dysmenorrhea.All the EA groups comparing to model control group:the B-EP content in Sanyinjian group and Xuanzhong group had increased significantly (P<0.01); and there were no statistical differences in increasing of B-EP content in Xuehai group and non-acupoint group (P>0.05).Comparing to the non-acupoint group, the B-EP content in Sanyinjian group and Xuanzhong group significantly increased(Sanyinjian group:P<0.01, Xuanzhong group:P<0.05).There were statistical differences between Sanyinjiao group and Xuehai group, and also between Sanyinjiao group and Xuanzhong group (P<0.01); and there were no significant differences between Xuanzhong group and Xuehai group (P>0.05).The results above suggest that:Acupuncture could adjust the B-EP content in PAG of rat with different effects. Sanyinjiao group and Xuanzhong group could significantly regulate the B-EP content in PAG, and Sanyinjiao group showed a better effect. But the Xuehai group and non-acupoint group hadn't changed significantly.5.3 Effect of electro-acupuncture on different acupoints on the Dyn content in PAG:Model control group comparing to the saline control group:the Dyn content in PAG increased, but had no statistical differences (P> 0.05), which meant that the Dyn content in PAG didn't increase significantly in the rat model of experimental dysmenorrhea.All the EA groups comparing to model control group:the Dyn content in Sanyinjian group and Xuanzhong group significantly increased (P<0.01); and there were no statistical differences in increasing of Dyn content in Xuehai group and non-acupoint group (P>0.05).Comparing to the non-acupoint group, the Dyn content in Sanyinjian group significantly increased (P<0.01).There were statistical differences between Sanyinjiao group and Xuehai group, Sanyinjiao group and Xuanzhong group (P<0.01); and there were no significant differences between Xuanzhong group and Xuehai group (P>0.05).The results above showed that:Acupuncture could adjust the Dyn content in PAG of the rat with different effects. Sanyinjiao group and Xuanzhong group could both regulate the Dyn content in PAG significantly, and Sanyinjiao group had a better effect. The Xuehai group and non-acupoint group showed no significant changes.5.4 Effect of electro-acupuncture on different acupoints on the EM content in PAG:Model control group comparing to the saline control group:the EM content in PAG increased, but had no statistical differences (P> 0.05), which meant that increasing of the EM content in PAG wasn't significant in the rat model of experimental dysmenorrhea.All the EA groups comparing to the model control group:EM content of each group all increased, but differences were not significant (P> 0.05).The experiment results above suggest that:Acupuncture on acupoints and non-acupoints could not improve the EM content in PAG of rats significantly.ConclusionBehavior response in rats showed that electroacupuncture on acupoints and non-acupoints innervated by the same nerve segment, all of which could alleviate dysmenorrhea reaction in rats with different effects. Sanyinjiao showed the best effect than Xuehai, Xuanzhong and non-acupoint, and the three groups had no significant differences. EA could adjust contraction of uterine smooth muscle and the content of pain-producing substances in uterus and the central pain modulation system to play an analgesic effect. However, acupuncture on different acupoints played different roles. Comparing to EA on Xuanzhong as non-relevant acupoint and non-acuppoint, EA on Sanyinjiao and Xuehai as relevant acupoints had more significant effect onκ-opioid receptor expression of dorsal horn of spinal cord in all segments, and Sanyinjiao has a best effect. Sanyinjiao and Xuanzhong as the special acupoints of relevant and non-relevant meridian could regulate the contents of endopioid peptide in PAG, and Sanyinjiao has a better effect. All of this implied that the existence of specificity of acupoint effect, the effect of acupoints was not only closely related to innervation of the nerve segment, but also "meridian" still played a key role, and the specificity of acupoint effect is relative, not absolute.
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