Tumor Necrosis Factor-alpha Contributes To The Pain Hypersensitivity Following Complete Freund's Adjuvant-induced Inflammatory Rats

Objectives:1.To investigate the characteristic of the CFA-induced inflammation pain and the expression and regulation of TNF-αin spinal dorsal by measuring the mechanical allodynia and immunohistochemistry.2. To investigate the role of TNF-αin the inflammation pain by administering anti-TNF-αreceptor monoclonal antibody (Etanercep) intrathecally (IT) and intraperitoneally (IP) .3. To investigate the afferent mode of the cytokine by nerve block experiment.Methods:1.48 Sprague-Dawley rats were randomly divided into 6 groups (1h,3h,1d,3d,7d,14d,n=8). 50% paw withdrawal threshold was test at respective time after injecting CFA 100μl into the planter surface of the rats' left hindpaw. After the nociceptive testing, thoracic and lumbar segments of the spinal cord were removed for immunohistochemistry and double labeling immunofluorescence.2. 48 Sprague-Dawley rats were randomly divided into 6 groups(n=8).Group A, saline administered intraperitoneally; Group B, Etanercep administered intraperitoneally; Group C, saline administered intraperitoneally and CFA was injected; Group D, Etanercep administered intraperitoneally and CFA was injected ; Group E, saline administered intraperitoneally; Group F, Etanercep administered intraperitoneally; Group G, saline administered intraperitoneally and CFA was injected; Group H, Etanercep administered intraperitoneally and CFA was injected.50% paw withdrawal threshold was test at respective time.3.Ten minutes before CFA was injected, Lidocaine was injected ipsilaterallyinto the sciatic notch for blocking the sciatic nerve. After 3 hours, thoracicand lumbar segments of the spinal cord were removed forimmunohistochemistry.Results:1. 50% paw withdrawal threshold was significantly lower after injecting CFA at respective time(P<0.05).Especially, at 1 day, the threshold was lowest. And then, the threshold recover gradually. The expression of TNF-αbecame lower than contralateral at 3 hours after injecting CFA . And the peak level at 3 days after injecting CFA. At 14 days, the expression of TNF-αwas comparable with the contralateral. By observing the double labeling immunofluorescence, we found the upregulated TNF-αwas mainly localized in the neurons and primary nerve terminals. Sparsely TNF-αwas expressed in the GFAP-immunoreactive cells or OX-42-immunoreactive cells.2. Injecting Etanercep intrathecally and intraperitoneally can both attenuate CFA-induced allodynia(P<0.05), and no differences between them(P>0.05).3. Blocking the sensory impulses from the sciatic nerve can not reduced TNF-αlevel in spinal cord at 3 hours after injecting CFA.Conclusions:1. There is special temporo-spatial pattern of TNF-αexpression and praxiology after injecting CFA.2. Injecting Etanercep intrathecally and intraperitoneally can both attenuate CFA-induced allodynia illustrate that TNF-αplay role for peripheral sensitization and central sensitization.3. Block nerve experiment can't reduced TNF-αlevel in spinal cord illustratethat the increased TNF-αmay not only be import by nerve afferenttransmission.