• Li Wan, Ailin Luo, Honghui Yu, and Yuke Tian.
• Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
• J Huazhong U Sci Med. 2005 Jan 1; 25 (2): 219-22.

AbstractTo study the mechanism of the innoxious touch-stimulus on the modulation of hyperalgesia and the expression of the C-fos and the nerve growth factor (NGF) receptor-TrkA in the spinal dorsal horn neurons following the chronic constriction injury (CCI) of the sciatic nerve in rats, 60 female Sprague-Dawley rats were randomly divided into sham-operation group and CCI group, with each group being further divided into 3 subgroups on the 7th, 14th and 28th day after operation (n = 10). The mechanical and the thermal withdrawal threshold were assessed following the touch stiumulation after the CCI, immunohistochemical methods were employed to observe the expression of the C-fos and TrkA in spinal dorsal horn. Our results showed that the hyperalgesia appeared on the 4th day and reached the maximal level on the 14th day after operation. The expression of the C-fos also increased significantly and reached its maximal level on the 14th day after the touch-stimulus. Meanwhile, the TrkA expression was elevated significantly in both groups, as compared with basic data, and the difference was statistically significant (P < 0. 05). It is concluded that the level of the C-fos expression changed with the paw withdrawal threshold variation and increased markedly following the innoxious touch-stimulus. The expression of the TrkA receptors also increased gradually following the development of the neuropathic pain. The results suggest that C-fos may play a crucial role in the development of the hyperalgesia in the earlier-time of the neuropathic pain, but TrkA receptors may be involved in the long-lasting adaptive changes of the central pathway in neuropathic pain.

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