• Megumi Omori, Masataka Yokoyama, Yoshikazu Matsuoka, Hiroyuki Kobayashi, Satoshi Mizobuchi, Yoshitaro Itano, Kiyoshi Morita, and Hiroyuki Ichikawa.
• Department of Anesthesiology and Resuscitology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1, Shikata-cho, Okayama City 700-8558, Japan.
• Brain Res. 2008 Jul 11;1219:26-31.

AbstractWe investigated changes in pain behavior after injection of acetic acid in the hindpaws of rats with L5 spinal nerve ligation (SNL)-induced neuropathy. We also examined immunoreactivity for acid-sensing ion channel 3 (ASIC3) in the dorsal root ganglion (DRG) of rats with L5 SNL. Two weeks after SNL, the withdrawal threshold to a mechanical stimulus was significantly lower in the SNL group than in the sham-operated group (n=9 per group, P<0.01). After acetic acid injection, spontaneous pain responses in the SNL group were significantly increased compared to those in the sham-operated group (n=5, P<0.05). L5 SNL significantly increased the proportion of total ASIC3-immunoreactive (ir) neurons in the ipsilateral L4 DRG compared to that in sham-operated rats (n=4, P<0.01). Analysis of cell size showed that the proportion of large (>1200 mm(2)) ASIC3-ir neurons in the ipsilateral L4 DRG significantly increased after L5 SNL (P<0.05). In the ipsilateral L5 DRG, the proportion of ASIC3-ir neurons was not significantly affected by treatment. However, L5 SNL significantly increased (P<0.01) the proportion of small (<1200 mm(2)) ASIC3-ir neurons and significantly decreased (P<0.01) the proportion of large ASIC3-ir neurons compared to proportions in sham-operated animals. These findings suggest that ASIC3 is associated with hyperalgesia in response to a chemical stimulus in the L5 SNL rat model.

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