The Experimental Study On The Difference Of Neuropeptide Expression In A Rat Model With Imbalance Of Dynamic And Static Forces

Objective: To investigate the expression of SP(substance P),CGRP(calcitonin generelated peptide),VIP(vasoactive intestinal peptide),NPY(neuropeptide Y)and its receptors Y1 R,Y2R in the hypothalamus,intervertebral disc and dorsal root ganglion of rats with IDD(intervertebral disc degeneration)and SHAM(sham operation).Meanwhile determine the mechanical pain and thermal pain threshold of both group rats and analyse the correlation between the expression of neuropeptides,Y1 R,Y2R and pain threshold.To further study the possible role of neuropeptides in the pathogenesis of intervertebral disc degeneration and discogenic back pain.Methods: 6-month-old female SD rats which were not pregnant were randomly divided into two groups: SHAM group(n=6)and IDD group(n=6).The mechanical pain threshold and thermal pain threshold of the two groups were measured 1 day preoperative and 12 weeks postoperative.Then the rats were executed,the expression of SP,CGRP,VIP,NPY and its receptors Y1 R,Y2R in the hypothalamus,intervertebral disc and dorsal root ganglion of the two groups were observed by immunohistochemistry.The MOD(mean optical density)of neuropeptides was used to analyze the relationship of the expression of SP,CGRP,VIP,NPY and its receptors Y1 R,Y2R between the hypothalamus,intervertebral disc and dorsal root ganglion.The relationship between the MOD of neuropeptides and mechanical pain threshold,thermal pain threshold was also analyzed.Results: At 12 weeks after dynamic and static instability operation,immunohistochemistry showed that the MOD values of SP,CGRP,VIP and NPY in the intervertebral disc of the IDD group were higher than in the SHAM group.The MOD value of Y1 R was lower than in the SHAM group(P<0.05);the MOD values of SP,CGRP and NPY in the DRG of the IDD group were higher than in the SHAM group.The MOD value of Y1 R in the DRG of the IDD group was lower than in the SHAM group(P<0.05).Pain detection showed that the mechanical pain threshold and thermal pain threshold of the rats in the IDD group were lower than in the SHAM group,and the difference was statistically significant(P<0.05).Correlation analysis showed that there was a positive or negative correlation between the MOD value of SP,CGRP,VIP,NPY,Y1 R and the mechanical pain threshold or thermal pain threshold in the hypothalamus,intervertebral disc and dorsal root ganglion of the two groups at 12 weeks after operation(P<0.05).Conclusions: The expression of neuropeptides in rats with intervertebral disc degeneration is increased and related to mechanical pain threshold and thermal pain threshold.We hypothesized that neuropeptides may be involved in the process of intervertebral disc degeneration and play a role in the regulation of discogenic back pain,but its specific mechanism needs to be further studied.