Effects Of Far And Near Acupoints On IL - 1β And PGE <2> Expression In Spinal Cord Of Rats With Nucleus Pulposus

OBJECTIVE:To explore the effects and mechanisms of electro-acupuncture (EA) on different acupoint modules in the rat model of inflammatory pain induced by autologus nucleus pulposus, we established a rat model and evaluated the effects of EA on pain-related behaviors, pathological changes of spinal cord and expression of interleukin-1 beta (IL-1 β) and (prostaglandin E2, PGE2) in the rat model of inflammatory pain induced by autologus nucleus pulposus.METHODS:In this study, a rat model of inflammatory pain was established, by which autologous nucleus pulposus obtained from the coccygeal intervertebral discs of the amputated tail in the same rat was relocated at the juncture of the L5 nerve root and the dural sac. Rats were randomly divided into normal, model, sham, EA 1, EA2 and EA3 groups. In EA 1 group, rats were needled at bilateral L5 Jiajixue (Ex-B 2), Dachangshu (BL 25), Weizhong (BL 40) and Kunlun (BL 60). In EA 2 group, rats were needled at bilateral Weizhong (BL 40) and Kunlun (BL 60). In EA 3 group, rats were needled at bilateral L5 Jiajixue (Ex-B 2) and Dachangshu (BL 25). EA stimulation was carried out between EA groups, once per day for 7 days. Mechanical withdrawal threshold and thermal withdrawal latencies from noxious stimulation were measured at 1 day preoperatively and at 3,5 and 7 days postoperatively. After 7 days of intervention, hematoxylin & eosin (HE) method was applied to observe the pathological changes of spinal cord, and enzyme-linked immunosorbnent assay (ELISA) methods were used to quantify IL-1 β and PGE2 in the spinal cord.RESULTS:1 Manifestation of pain-related behaviors in ratsAfter transplantation of autologus nucleus pulposus, mechanical withdrawal threshold of rats in the model group decreased in the hindpaws at 3 days postoperatively when compared with that in the normal group (P<0.01) lasting at 7 days postoperatively. Thermal withdrawal latencies of rats in the model group decreased in the hindpaws at 5 days postoperatively, and exhibited evidence of hyperalgesia in responses to thermal withdrawal latencies when compared with those in the normal group (P<0.05). After administration of EA among EA 1, EA 2 and EA 3 groups, mechanical withdrawal threshold and thermal withdrawal threshold in the EA 1, EA 2 and EA 3 groups were higher than that in the model group (P<0.05;P<0.01). No obvious differences were found among EA 1, EA 2 and EA 3 groups. However, the tendency of EA 1 and EA 3 group were more obvious than that in EA2 group.2 Pathological changes of spinal cord in ratsPathological changes of the spinal cord were evaluated by hematoxylin and eosin (HE) stain at 7 days postoperatively. The inflammatory edema of the spinal cord can be observed in model group. The nerve myelin sheath disintegrates and necrosis, and the nerve ganglion cells had numerous cytoplasm, and some nucleus disappeared. The stimulation of autologus nucleus pulposus triggered the extent of damage of the spinal cord. Although damages to the spinal cord could be observed in EA 1, EA 2 and EA 3 groups, EA treatment reversed the extent of damage to the spinal cord induced by autologous nucleus pulposus.3 Effects of EA on IL-1 β in the spinal cordAt 7 days postoperatively, expression of IL-1β in the spinal cord in each group was quantified by ELISA. The ELISA tests showed that there was an increase of IL-1β level in the spinal cord of rats in the model group than that in normal group (P<0.01). EA treatment reversed the increase in IL-1β level in the spinal cord in model group. The expression level of the spinal IL-1 β was significant lower in the EA 1, EA 2 and EA 3 groups. However, the tendency of EA 1 and EA 3 group were more obvious than that in EA 2 group.4 Effects of EA on PGE2 in the spinal cordAt 7 days postoperatively, expression of PGE2 in each group was quantified by ELISA. Compared with the normal group, the expression levels of the PGE2 was higher in the model group (P<0.01). And it was reversed by EA. No significant differences in the expression level of PGE2 were found among EA 1, EA 2 and EA 3 groups. However, the tendency of EA 1 and EA 3 group were more obvious than that in EA 2 group.CONCLUSION:The model of neuropathic pain induced by autologus nucleus pulposus in rats is successful. Stimulation of autologus nucleus pulposus could up-regulate the expression levels of PGE2 and IL-1β in the spinal cord, trigger the extent of damage of the spinal nerve root, DRG and spinal cord and induce evidence of hyperalgesia in responses to thermal and mechanical withdrawal latencies. EA at "distant acupoints+local acupoints", "distant acupoints" and "local acupoints" could reverse the up-regulation of IL-1β and PGE2 level in spinal cord and alleviate the extent of hyperalgesia in responses to mechanical withdrawal threshold and thermal withdrawal threshold, which might be involved in EA analgesia. No significant differences were found among EA 1, EA 2 and EA 3 groups. However, EA 1 and EA 3 groups tended to have more obviously therapeutic effects than that in EA 2 group.