Zhang Wei, Liu Yue, Zhao Xin, Gu Xiaoping, Ma Zhengliang
From the Department of Anesthesiology, Affiliated Drum Tower Hospital of Medical Department of Nanjing University, Nanjing, Jiangsu, People's Republic of China.
Anesth Analg. 2014 Jul;119(1):179-185. doi: 10.1213/ANE.0000000000000179.
The fact that transient receptor potential ankyrin 1 (TRPA1) on the peripheral terminals could attenuate hyperalgesia is widely accepted, but the effect of spinal TRPA1 in the modulation of hyperalgesia has not been fully demonstrated. In the present study, we investigated the effect of intrathecal (i.t.) administration TRPA1 antagonists on chronic pain and expression of TRPA1 and phosphorylation N-methyl-D-aspartate receptor 2B subunit (p-NR2B) in the spinal cord with chronic compression of the dorsal root ganglia (CCD) in rats.
The study was conducted in 2 parts. Part 1: Sixteen rats were divided into 2 groups (n = 8 each): a sham group and CCD group. Paw withdrawal mechanical thresholds (PWMT) were measured at baseline and 1, 3, 7, 10, 14, and 21 days after CCD. Sixteen other rats were used to evaluate expression of TRPA1 and p-NR2B in spinal cord on the seventh and 14th days after CCD; Western blotting was used to evaluate expression levels (n = 4 each). Part 2: 40 rats were divided into 5 groups (n = 8 each): CCD group, CCD + Vehicle group, CCD + HC-030031(10 μg, i.t.) group, CCD + HC-030031(25 μg, i.t.) group, and CCD + HC-030031(50 μg, i.t.) group. PWMTs were measured at baseline and 0.5, 1, 2, 4, and 6 hours after i.t. HC-030031 on the third, seventh, 10th, and 14th days after CCD. Another 48 rats were used to evaluate expression of TRPA1 and p-NR2B in spinal cord 2 hours after injection on the seventh and 14th days after CCD in groups CCD, CCD + Vehicle, and CCD+ HC-030031(50 μg, i.t.) using Western blotting (n = 4 each).
Compared with the sham group, PWMT was significantly decreased, and protein expression of TRPA1 and p-NR2B were upregulated, in spinal cord on the seventh and 14th days after CCD operation. TRPA1 antagonists (HC-030031, 50 μg, i.t.) increased the PWMT after CCD and downregulated the protein level of TRPA1 and p-NR2B in spinal cord at 2 hours after the injection on the seventh and 14th days after CCD.
These data demonstrated that the i.t. administration of TRPA1 antagonists could attenuate neuropathic pain in CCD rats, and this effect could be partially reduced by p-NR2B receptor expression in spinal cord.
外周神经末梢上的瞬时受体电位锚蛋白1（TRPA1）可减轻痛觉过敏这一事实已被广泛接受，但脊髓TRPA1在痛觉过敏调节中的作用尚未得到充分证实。在本研究中，我们研究了鞘内注射TRPA1拮抗剂对大鼠背根神经节慢性压迫（CCD）模型中慢性疼痛以及脊髓中TRPA1表达和N-甲基-D-天冬氨酸受体2B亚基磷酸化（p-NR2B）的影响。
本研究分两部分进行。第一部分：16只大鼠分为2组（每组n = 8）：假手术组和CCD组。在CCD术后基线及1、3、7、10、14和21天测量爪部缩足机械阈值（PWMT）。另外16只大鼠用于评估CCD术后第7天和第14天脊髓中TRPA1和p-NR2B的表达；采用蛋白质印迹法评估表达水平（每组n = 4）。第二部分：40只大鼠分为5组（每组n = 8）：CCD组、CCD + 溶剂组、CCD + HC-030031（10 μg，鞘内注射）组、CCD + HC-030031（25 μg，鞘内注射）组和CCD + HC-030031（50 μg，鞘内注射）组。在CCD术后第3、7、10和14天，鞘内注射HC-030031后基线及0.5、1、2、4和6小时测量PWMT。另外48只大鼠用于通过蛋白质印迹法评估CCD术后第7天和第14天在CCD组、CCD + 溶剂组和CCD + HC-030031（50 μg，鞘内注射）组中注射后2小时脊髓中TRPA1和p-NR2B的表达（每组n = 4）。
与假手术组相比，CCD术后第7天和第14天脊髓中的PWMT显著降低，TRPA1和p-NR2B的蛋白表达上调。TRPA1拮抗剂（HC-030031，50 μg，鞘内注射）可提高CCD术后的PWMT，并在CCD术后第7天和第14天注射后2小时下调脊髓中TRPA1和p-NR2B的蛋白水平。
这些数据表明，鞘内注射TRPA1拮抗剂可减轻CCD大鼠的神经性疼痛，且这种作用可能部分通过脊髓中p-NR2B受体表达降低来实现。
