| Contralateral allodynia and central change in the chronic post-ischemic pain model rats. |
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Kyung Hwa Kwak, Kyung Young Jung, Jy Young Choi, Taeha Ryu, Jin Seok Yeo, Sung Sik Park, Dong Gun Lim, Si Oh Kim, Woon Yi Baek, Jung Gil Hong |
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Department of Anesthesiology and Pain Medicine, Kyungpook National University School of Medicine, Daegu, Korea. dglim@mail.knu.ac.kr |
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| Abstract |
BACKGROUND
Mirror-image allodynia is a mysterious phenomenon that occurs in association with many clinical pain syndromes including complex regional pain syndromes (CRPS). Underlying mechanisms for the development of such pain are still a matter of investigation. Several studies suggest that activation of the N-methyl-D-aspartate (NMDA) receptor is essential for central sensitization as a base for persistent pain. The aim is to assess whether alteration of NMDA receptor expression correlates with the contralateral allodynia in the chronic post-ischemia pain (CPIP) model rats representing CRPS-Type I. METHODS: Application of a tight-fitting tourniquet for a period of 3 hours before reperfusion produced CPIP in male Sprague-Dawley rats. The mechanical paw withdrawal thresholds to von Frey stimuli (using a dynamic plantar aesthesiometer) were measured as pain indicators in ipsilateral and contralateral hindpaws. Phosphorylation of the NMDA receptor 1 subunit (pNR1), assessed with Western blot, was measured in the contralateral L4-6 spinal cord.
RESULTS
Ipsilateral and contralateral mechanical allodynia is present at 4 hours after reperfusion, peaked at 3 days, and continued for 7 days after reperfusion. The relative density of pNR1 of CPIP rats significantly decreased in the contralateral L4-6 spinal cord compared to baseline value (P < 0.05). There was significant correlation between paw withdrawal threshold and the relative density of pNR1 (ipsilateral; R2 = 0.75, P < 0.01, contralateral; R2 = 0.60, P < 0.01). CONCLUSIONS: These data suggest that pNR1 is correlated to the contralateral mechanical allodynia in CPIP rats. |
| Key Words:
Chronic post-ischemia pain; Complex regional pain syndrome-type I; NMDA receptor; Mirror-image allodynia |
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