部分坐骨神经损伤模型大鼠痛阈及脊髓背根神经节TRPA1 mRNA表达的变化

Pain threshold of rats with spared nerve injury and changes of TRPA1 mRNA expression in spinal dorsal root ganglion

目的观察部分坐骨神经损伤(SNI)模型大鼠的痛阈以及造模后不同时间点大鼠脊髓第4、5颈椎背根神经节(DRG)部位的瞬时受体电位通道A1(TRPA1)mRNA的表达情况,探讨外周TRPA1 mRNA在神经病理性疼痛(NP)模型不同阶段中的作用。方法选择30只健康成年雄性SD大鼠,质量200~230 g,随机分为三组:对照组6只、假手术组6只和SNI模型组18只。SNI模型组大鼠做左侧腓总神经、胫神经结扎切断,保留腓肠神经;假手术组大鼠切开皮肤肌肉找到神经后不结扎直接缝合切口;对照组不做任何处理。在术前3、1 d及术后1、3、5、7、9、12、14 d检测三组大鼠的双侧后肢机械缩足反射阈值(MWT)。SNI模型组术后1、3、5、7、14 d测定机械痛阈后各处死3只大鼠;假手术组、对照组各处死3只大鼠。取大鼠的术侧第4、5颈椎DRG,采用荧光定量聚合酶链式(q-PCR)反应检测TRPA1 mRNA的表达情况。结果SNI模型组术后各时点左后肢MWT值呈进行性下降,与假手术组比较,差异有统计学意义(P<0.01),表现出明显的术后痛;SNI模型组各时点MWT值与对照组比较,差异有统计学意义(P<0.01);SNI模型组每2个相邻时间点MWT的下降值比较,差异均有统计学意义(P均<0.05)。q-PCR结果显示,正常大鼠DRG有TRPA1 mRNA表达,假手术组TRPA1 mRNA表达水平与对照组比较差异未见统计学意义(P>0.05)。与假手术组比较,SNI模型组术后1、3 d TRPA1 mRNA水平均增高,术后7 d TRPA1 mRNA下降,差异有统计学意义(P<0.01)。结论SNI模型大鼠产生NP,外周TRPA1 mRNA参与SNI模型疼痛的产生和维持,且其在不同阶段发挥的作用不同。

Objective To observe the pain threshold of spared nerve injury (SNI) rats and the transient receptor potential cation channel subfamily A member 1 (TRPA1) mRNA expression of dorsal root ganglion (DRG) in the 4th cervical vertebra and the 5th cervical vertebra in rats at different time points after modeling;and to discuss the significance of peripheral TRPA1 mRNA in different stages of neuropathic pain model. Methods Thirty healthy adult male Sprague-Dawley rats, weighing 200-230 g, were selected and randomly divided into three groups: control group (6 cases), sham operation group (6 cases) and spared nerve injury model group (SNI group, 18 cases). In SNI group, the left common peroneal nerve and the sacral nerve were ligated, but the sural nerve was preserved. In the sham operation group, the skin muscles were dissected and the nerves were not ligated, and the incision was directly sutured. Rats in control group were not given any treatments. All rats were tested for bilateral hind limb mechanical withdrawal threshold (MWT) 3 days and 1 day before surgery, and 1, 3, 5, 7, 9, 12, 14 days after surgery. Three rats were sacrificed in sham operation group and control group, respectively. At 1, 3, 5, 7 and 14 days after treatment, 3 rats of SNI group were sacrificed everyday. The DRGs in the 4th cervical vertebra and the 5th cervical vertebra of the rats were taken and the expression of TRPA1 mRNA was detected by quatitative-polymerase chain reaction (q-PCR). Results The MWT values of the left hind limbs in SNI group were decreased progressively after SNI, which were significantly different from sham operation group (P<0.01), showing obvious postoperative pain. MWT values at each time point of SNI group were significant different from sham operation group (P<0.01). There was a significant difference in the decrease between each adjacent time point in SNI group (P<0.05). The results of q-PCR showed that TRPA1 mRNA was expressed in DRG of normal rats. There was no significant difference in the expression of TRPA1 mRNA between sham operation group and control group (P>0.05). Compared with the sham operation group, the level of TRPA1 mRNA was significantly increased 1 day and 3 days after SNI, and the TRPA1 mRNA was significantly decreased 7 days after surgery (P<0.01). Conclusions SNI model rats have neuropathic pain. Peripheral TRPA1 mRNA participates in the generation and maintenance of pain in SNI model, and its roles in different stages are different.