Effect of nucleus pulposus allografted into sciatic nerve on pain threshold in rats

Objective To observe the effect of nucleus pulpsus allografted the sciatic nerve on pain threshold in rats,so as to provide theoretical evidence for discogenic pain.Methods The expriment was carried out in the animal experimental center of Xuanwu Hospital,Capital University of Medical Sciences.Twenty-four male Sprague-Dawley rats were randomly divided into four groups with 6 rats in each:sham-operated group,fat group,muscle group and nucleus pulpsus group.The allografted fat,muscle and nucleus pulpsus were provided by the other 3 male SD rats.Rats in the sham-operated group were given an sciatic nerve exposure without any graft implantatoin.In the fat group,muscle group and nucleus pulpsus group,rats had allografts of adipose tissue(approximately 10 mg),muscly tissue(approximately 10 mg) and nucleus pulposus(approximately 10 mg) implanted into sciatic nerve,respectively.Preoperatively and 3,5,7,10,15,20,25,30 and 35 days postoperatively,the mechanical stimulation of both hind paws were observed.Using microscope try to find out the histological changes of sciatic nerve.Results All the 24 rats were involved in the analysis of results.The postoperative threshold values of rats to mechanical stimulation in the sham-operated group,fat group and muscle group were not significantly different from the preopertive ones(P 0.05).In the nucleus pulposus group,there was mechanical hyperalgesias after nucleus pulposus allografted into the sciatic nerve(P0.05),especially in 7~10 day after surgery.Inflammation,edema,lymphocyte increasing and swelling are found around the sciatic nerve allografted nucleus pulposus especially in 10 days after surgery too.Conclusion Nucleus pulposus allografted into the sciatic nerve can lead to the hyperalgesia of both feet of rats,which may be one of the reasons for radicular pain of a lumbar disc herniation resulted from nucleus pulposus.