Anterograde TNFα transport from rat dorsal root ganglion to spinal cord and injured sciatic nerve

Tumor necrosis factor-alpha (TNFalpha) is a key modulator of painful peripheral nerve injury. We have previously shown that a tracer of TNFalpha injected at the site of rat sciatic nerve injury undergoes retrograde axonal transport to the dorsal root ganglia (DRG). To further understand the role of TNFa in DRG, we injected rat L5 DRG with biotinylated TNFalpha, neurobiotin, or vehicle, and detected translocation of the biotin tag by avidin-biotin histochemistry. Biotinylated TNFalpha was transported intraaxonally toward the periphery of both normal and injured nerves. It also reached the dorsal horn of the spinal cord in injured rats, but not in control rats. These findings highlight a dynamic process of TNFalpha axonal transport in the peripheral neural axis, and help explain activation of central cytokines in the pathogenesis of painful neuropathy. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.