Anti-TNF-α Antibody Reduces Pain-Behavioral Changes Induced by Epidural Application of Nucleus Pulposus in a Rat Model Depending on the Timing of Administration

In Brief Study Design. An experimental animal study. Objective. To study if antitumor necrosis factor-alpha (TNF-α) antibody, which is administered at different times, reduces the pain behavior induced by application of nucleus pulposus (NP) to the nerve root. Summary of Background Data. Treatment with TNF-α inhibitor reduces the pain-related behavior induced by epidural application of NP in rats. Methods. Left L5 partial laminectomy was performed and NP was applied to the L5 nerve root in 24 rats. The rats were divided into 4 groups. In 3 groups, anti-rat TNF-α antibody was intravenously administered immediately after, or 6 or 20 days after NP application. The fourth group was not treated with anti-rat TNF-α antibody (untreated rats). The withdrawal threshold of the plantar surface was determined 1 day before up through 28 days after NP application. Results. The withdrawal threshold of rats that had been treated with anti-rat TNF-α antibody immediately after or 6 days after, but not 20 days after, NP application, was significantly higher than that of the untreated rats. Conclusions. Anti-TNF-α antibody reduced allodynia only when it was administered soon after the onset of allodynia. Late administration of anti-TNF-α antibody did not have an antiallodynic effect. Rat anti-TNF-α antibody reduced the allodynia induced by epidural application of nucleus pulposus, when the antibody was applied immediately after or 6 days after the epidural application, but not at 20 days after epidural application. TNF-α may play an important role in the production of allodynia only in the early stage.