| Background:Discogenic low back pain(LBP) is popular and recurrent disease. Owing to lumbar intervertebral disc degeneration, it maybe appear low back pain and (or) sciatica. LBP could result in human activitys function so that it bring out disasters.Lumbar disc herniation, which is one of the anatomic findings that can be associated with low back and leg pain, is a common clinical entity that can lead to significant symptoms in patients. However, the pathomechanism of pain secondary to a lumbar disc herniation is still unknown.Clinical reports have suggested that mechanical compression of the nerve root in lumbar disc herniation patients is not always the cause of radicular pain and dysfunction. The pathomechanisms of radicular pain due to lumbar disc herniation, nerve root irritation induced by proteoglycans released from disc, an autoimmune response from exposure of disc tissues,or an increase of lactic acid and a lower pH around the nerve root, have been reported. In general, these reports indicate that the mechanisms underlying radicular pain may not be due to a mechanical compression or deformity of the nerve root, but due to local chemical contributions. However, Olmarker et al, for the first time,demonstrated that nucleus pulposus itself produces electrophysiologic and histologic changes consistent with nerve root damage without apparent mechanical compression. Although little is known about how the intervertebral disc is involved in pain mechanisms, there have been a few reports regarding the possible contribution of chemicals such as phospholipase A2 (PLA2), cytokines, and nitric oxide (NO) in lumbar herniated disc materials. In addition, it was reported that the allograft of nucleus pulposus (NP) and NP with anulus fibrosus (AF) placed in the lumbar epidural space of the rat results in mechanical and thermal hyperalgesia, respectively. Both of these are considered to be manifestations of persistent or chronic pain.The experiments involved epidural administration and investigate the effects of NP placed in the lumbar epidural space of the rat results in mechanical and thermal hyperalgesia, Given that,the relation between the hyperalgesia and activation of SP and CGRP.The purposes of this study were threefold: First, to evaluate whether the allografted intervertebral disc materials placed in the lumbar epidural space of the rat results in mechanical and thermal hyperalgesia; second, to determine whether the resultant hyperalgesia is influenced by SP and CGRP; and, finally, to aid in our understanding of the pathomechanisms of Salvia miltiorrhiza using to a herniated intervertebral disc.Objective:1. To observe the effect of nucleus pulposus allografted into the epidural space on pain threshold in rats; to obseve the effects of SP and CGRP expression of dorsal root ganlion neurons in rats of nucleus pulposus allografted into epidural space, so as to provide theoretical evidence for discogenic pain.2. To observe the effects of Salvia miltiorrhiza applied into epidural space of rats by allografted nucleus pulposus into epidural space on the expressions of SP and CGRP in rat's DRG neurons, so as to provide theoretical evidence for the treatment of discogenic pain.Methods:1. Eighteen male Sprague-Dawley rats were randomly divided into three groups with 6 rats in each: sham-operated group, fat group and nucleus pulposus group. The allografted fat and nucleus pulposus were provided by the other 3 male SD rats. Rats in the sham-operated group were given an epidural space exposure without any graft implantation. In the fat group and nucleus pulposus group, rats had allografts of adipose tissue (approximately 3.0-4.0 mg) and nucleus pulposus (approximately 3.0-4.0 mg) implanted into epidural space, respectively. Preoperatively and at 3, 7, 15 and 30 days postoperatively, the responses of tail to transcutaneous electrostimulation, thermal stimulation and mechanical stimulation were observed; 30 days postoperatively, the expressions of SP and CGRP in L4-5 Dorsal Root Ganglion (DRG) neurons were detected by immunohistochemistry method. In addition, the structure of epidural space were observed.2. Twenty-four male Sprague-Dawley rats were randomly divided into four groups with 6 rats in each: nucleus pulposus + nature saline group(SG group), nucleus pulposus + Salvia miltiorrhiza group (DG group), nucleus pulposus + Dexamethasone group(NS group), and nucleus pulposus + no drug group (WG group). Nature saline, Salvia miltiorrhiza and Dexamethasone were administered by injecting into epidural space once per day for 14 days according to different groups, respectively. Before and after drug injection, the posterior Paw Withdrawal Mechanical Threshold (PWMT) was measured by Von Frey hair, and the expressions of SP and CGRP in L4-5 dorsal horn neurons of spinal cord were detected by immunohistochemistry method of 14 days after drug injection. Results:1. The postoperative threshold values of rats to thermal stimulation and and mechanical stimulation in the sham-operated group and fat group were not significantly different from the preoperative ones (P>0.05). In the nucleus pulposus group, there were mechanical and thermal hyperalgesias 2 days after nucleus pulposus allografted into the epidural space until 30 days postoperatively (P<0.05); 30 days postoperatively, the SP and CGRP expressions in the sham-operated group and fat group were not significantly different (P>0.05). The SP and CGRP expressions of DRG neurons in nucleus pulposus group were significantly increaced compared with sham-operated group, fat group (P<0.05), respectively.2. 14 days after drug injection, the expressions of SP and CGRP in dorsal horn of spinal cord in WG group was stronger than MG group,DG group,SG group, respectively. (p<0.05); but the expressions of SP and CGRP in DG goup was less than NS without significant difference compared with MG group (p>0.05).Conclusion:1. Nucleus pulposus allografted into the epidural space can lead to the hyperalgesia;The SP and CGRP expressions of DRG neurons in rats can increase because nucleus pulposus were allografted into the epidural space, which may be the reason for radicular pain of a lumbar disc herniation.2. Salvia miltiorrhiza or Dexamethasone or Nature saline inject into the epidural space can reduce the SP and CGRP expressions in rat's DRG...
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