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目的:观察P物质(Substance P,SP)在慢性坐骨神经压迫损伤(chronic constriction injury,CCI)模型脊髓中表达的变化,探讨电针镇痛的机制是否与脊髓背角中SP表达的变化有关。方法:选择32只雄性、体重180-200 g的SD大鼠,并将其随机均分为4组(n=8)。空白组(Con组)为正常痛阈值大鼠;假电针组(CCI+A组)在损伤的坐骨神经旁置入电针,但无电流刺激;2 Hz组和100Hz组分别给予相应频率电流刺激30 min。在实验开始前和术后1、4、7、14、20、22天记录大鼠的热缩足反射潜伏期(Paw Withdrawal Latency,PWL)和机械刺激缩足反射阈值(Paw Withdrawal Threshold,PWT)。免疫组化方法检测脊髓背角SP的表达。结果:术后20天,电针治疗后,100 Hz组和2 Hz组PWT分别为(7.33±1.42)g和(7.80±1.42)g,均显著高于假电针组(2.60±1.46)g,差异有统计学意义(P<0.05)。100 Hz组在术后20天后和2 Hz组在术后14天后PWL值均显著高于假电针组,差异有统计学意义(P<0.05)。免疫组化显示:2 Hz组和100 Hz组大鼠脊髓背角中P物质阳性细胞显著低于假电针组(P<0.05)。结论:坐骨神经旁电针刺激能够显著减轻CCI模型大鼠热痛觉及机械痛觉过敏,其机制可能与抑制脊髓背角SP的表达有关。
Objective: To observe the changes of substance P (SP) in the spinal cord of chronic constriction injury (CCI) model and to explore whether the mechanism of electroacupuncture analgesia is related to the change of SP expression in spinal dorsal horn. Methods: Thirty-two male SD rats weighing 180-200 g were randomly divided into 4 groups (n = 8). The rats in the blank control group (Con group) were given normal pain threshold. Electroacupuncture (EA) was injected beside the injured sciatic nerve in the sham acupuncture group (CCI + A group) 30 min. The Paw Withdrawal Latency (PWL) and Paw Withdrawal Threshold (PWT) were recorded before and at 1, 4, 7, 14, 20 and 22 days after the operation. Immunohistochemistry was used to detect SP expression in spinal dorsal horn. Results: After 20 days of electroacupuncture, the PWT in the 100 Hz group and the 2 Hz group were (7.33 ± 1.42) g and (7.80 ± 1.42) g, respectively, which were significantly higher than that of the sham acupuncture group (2.60 ± 1.46 g , The difference was statistically significant (P <0.05). The PWL values of 100 Hz group at 20 days and 2 Hz group at 14 days after operation were significantly higher than that of the sham acupuncture group (P <0.05). Immunohistochemistry showed that in the 2 Hz group and the 100 Hz group, the substance P positive cells in the dorsal horn of spinal cord were significantly lower than that of the sham acupuncture group (P <0.05). Conclusion: Electroacupuncture at the sciatic nerve can significantly reduce thermal pain and mechanical hyperalgesia in CCI model rats, which may be related to the inhibition of SP expression in spinal dorsal horn.