Effect of nucleus pulposus allografted into epidural space on the expressions of SP and CGRP in rat's DRG neurons

Abstract

In this study, we implant allogenic nucleus pulposus into the epidural space to investigate the expressions of SP and CGRP in rat's DRG neurons, so as to provide theoretical evidence for discogenic pain. Male Sprague-Dawley rats were randomly divided into four groups with 6 rats in each: fat + nature saline group(FS group), fat + collagenase group (FE group), nucleus pulposus + nature saline group(NS group), and nucleus pulposus + collagenase group (NE group). The allografted fat and nucleus pulposus were provided by the other 8 male SD rats. The responses of tail to mechanical stimulation were observed before surgery and at 7th and 15th day after surgery, and the L6-S1 DRGs were separated, and the expressions of SP and CGRP in DRGs were detected by using immunohistochemistry method 15th day after surgery. We got these results: (1) The postoperative threshold values of rats to mechanical stimulation in the NS group were significantly decreased when compared with the preoperative ones (P<0.05), while other groups had no significant change(p＞0.05); At 7th and 15th day after surgery, the threshold in the NS group were significantly lower than in other groups(P<0.05). (2) At 15th day after surgery, the expressions of SP and CGRP in DRGs in NS group was stronger than FS group (p＜0.05); but the expressions of SP and CGRP in NE group was less than NS without significant difference compared with FS group (p＞0.05). The outcomes from our study indicated that Nucleus pulposus allografted into the epidural space can increase the SP and CGRP expressions in DRG which maybe lead to rat's allodynia.