Experimental neurology
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Experimental neurology · Mar 2013
The up-regulation of IL-6 in DRG and spinal dorsal horn contributes to neuropathic pain following L5 ventral root transection.
Our previous works have shown that pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) plays an important role in neuropathic pain produced by lumber 5 ventral root transection (L5-VRT). In the present work we evaluate the role of interleukin-6 (IL-6), another key inflammatory cytokine, in the L5-VRT model. We found that IL-6 was up-regulated in the ipsilateral L4 and L5 dorsal root ganglian (DRG) neurons and in bilateral lumbar spinal cord following L5-VRT. ⋯ Intrathecal administration of IL-6 neutralizing antibody significantly delayed the induction of mechanical allodynia in bilateral hindpaws after L5-VRT. Furthermore, inhibition of TNF-α synthesis by intraperitoneal thalidomide prevented both mechanical allodynia and the up-regulation of IL-6 in DRGs following L5-VRT. These data suggested that the increased IL-6 in afferent neurons and spinal cord contribute to the development of neuropathic pain following motor fiber injury, and that TNF-α is responsible for the up-regulation of IL-6.
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Experimental neurology · Mar 2013
Re-innervation patterns by peptidergic Substance-P, non-peptidergic P2X3, and myelinated NF-200 nerve fibers in epidermis and dermis of rats with neuropathic pain.
Nerve endings in the epidermis, termed nociceptors, conduct information on noxious stimuli to the central nervous system. The precise role of epidermal nerve fibers in neuropathic pain is however still controversial. Here, we have investigated the re-innervation patterns of epidermal and dermal nerve fibers in a rat neuropathic pain model. ⋯ However, the density of NF-200-IR fibers in the center area reached control levels at 10 weeks PO. No changes were found in the densities of any of the fibers in the medial and lateral parts of the foot sole. The present results suggest that after peripheral nerve injury, specific nerve fibers have different re-innervation patterns in the epidermis and dermis and that they might be involved in the development of neuropathic pain.