Experimental study for elucidation of the onset mechanism in the phantom pain

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We attempted to develop an experimental animal model for peripheral neuropathic pain including the phantom pain. Under anesthesia, median, ulnar and raidiar nerves of one side of the rat (SD and hairless) were cut (group 1) or pull out (group 2). Sensitivity of the fore paw to mechanical stimulation was tested with von Frey hair for the next 5 months in two groups. The general behavior of each rat was noted during the entire test period.Following arm denervation, autotomy in 50% (group 1) and 20% (group 2) exploded. In the hairless rat, the ulcer of the skin was observed in 50% (both group). The test with mechanical stimulation in all groups did not produce a mechanical allodynia. Seven days following axotomy of the nerves, some large and medium sized cells in the dorsal root ganglia (C4〜Th1) displayed neuropeptide Y (NPY)-like immunoreactivity (IR), and marked increases in the numbers were observed for the next 5 months. The number of NPY-IR cells in the stellate ganglion (SG) increased in the group 2. A few strong staining cells for the nicotinamaide adenin dinucleotide phosphate ? Diaphorase (NADPH-d) were observed in the SG of the group 1 for the next 7 days. NADPH-d staining cells were not detected in the normal rat SG.We concluded that the study of the neuropathic pain including the phantom pain must be done using different species and families.