Changes of 5-hydroxytryptamine contents in spinal cord dorsal horns of paclitaxel induced neuropathic pain rats

Objective To investigate the changes of 5-hydroxytryptamine(5-HT) contents in spinal cord dorsal horns of paclitaxel induced neuropathic pain rats.Methods Fifty-four male SD rats weighing about 300 g were randomly divided into 3 groups(n=18):normal control group(group A);vehicle group(group B) and paclitaxel group(group C).Rats in group C were injected intraperitoneally with paclitaxel 1.0 mg·kg~(-1)·d~(-1) to induce peripheral neuropathic pain.Mechanical withdrawal thresholds(MWT) were measured on 1 d before drug injection,3,5,7,9,11,14,18 and 21 d after injection.Four rats in each group were sacrificed on 1d before and 7,14 and 21 d after paclitaxel injection.5-HT contents in dorsal horns of spinal cord were assayed using high performance liquid chromatography with fluorescence detector.Right sciatic nerves of rats were collected on the 14th day after paclitaxel injection;transmission electron microscope was used to observe the damage of sciatic nerves.Results Compared with group A and B,MWTs in group C decreased significantly on day 7 and continued to 21st day after injection(P0.05).Electron photomicrographs of the sciatic nerves showed damage of nerve fibers 14d post drug injection in group C,while there was no destruction in the groups A and B.Compared with group A and B,5-HT in group C were significantly upregulated from the 7th till 21st day after drug injection(P0.05).5-HT in group C showed a strong negative linear correlation with mechanical withdrawal thresholds(r=-0.981,P 0.05).Conclusion Paclitaxel induced significant upregulation of 5-HT in spinal cord dorsal horn in rats,which might play a role in the pathogenesis of paclitaxel induced neuropathic paia