TAC1 and neuropathic pain: It has been reported that miR-500 is downregulated in rat DRG after sciatic nerve resection at 4, 7 and 14 days53 and in the spinal cord dorsal horn neurons 7 days after CCI of sciatic nerve.50 How this relates to neuropathic pain is not yet clear, but there is some evidence that miR-500 downregulates the neurokinin-1 (substance P) receptor.54 Activation of this receptor by substance P produces mechanical hyperalgesia and allodynia,55 and these molecules have been implicated in neuropathic pain.