鞘内联合应用吗啡和氯胺酮对神经痛大鼠脊髓P物质表达的影响

目的研究鞘内联合应用吗啡和氯胺酮对神经痛大鼠脊髓P物质表达的影响。方法12只Wistar大鼠,体质量220~260 g,制备坐骨神经结扎模型并鞘内置管,随机分为4组(n=3):B组为空白对照组;C组鞘内注射生理盐水10μL;M组鞘内注射吗啡20μg;KM组鞘内注射吗啡10μg和氯胺酮25μg。坐骨神经结扎术后第4天开始鞘内给药,1次/d,连续7 d。用药7 d后处死大鼠,取腰段脊髓,免疫组化法测定脊髓P物质的含量。结果C组P物质表达明显低于B组(P<0.05)和KM组(P<0.01);KM组P物质表达明显高于M组(P<0.05)。结论鞘内联合应用吗啡和氯胺酮的抗伤害性作用,可能与其增加脊髓背角P物质的含量有关;脊髓背角P物质含量减少,可能介导慢性坐骨神经损伤后的痛敏持续状态。

Effect of intrathecal morphine and ketamine on substance P expression in the dorsal horn of neuropathic rats

Objective To study the effect of intrathecal morphine and ketamine on substance P(SP)immunohistochemical staining in the dorsal horn of neuropathic rats.Methods 12 wistar rats weighing 220～260 g were prepared for placing loosely constrictive ligatures around the common sciatic nerves,and intrathecal implantation of a catheter.The rats were randomly allocated into four groups(n=3):group B(vehicle,no drugs available),group C(saline 10 μL),group M(morphine 20 μg),group KM(morphine 10 μg and ketamine 25 μg).Morphine and ketamine were administrated intrathecally once a day for 7 days on the forth day after operation 7 days later,the rats were decapitated and the lumbar spinal cord were removed.SP in spinal cord were measured by immunohistochemistry.Results Immunostaining density of SP in group C decreased compared with group B(P<0.05)and group KM(P<0.01).SP staining density in group KM was significantly higher than that in group M(P<0.01).Conclusion The antinociceptive mechanism of intrathecal morphine and ketamine was related to the increase of SP staining in lumbar spinal cord,however decrease of SP in spinal cord may mediate pain sensitivity after chronic sciatic nerve injury.