Contralateral allodynia and central change in the chronic post-ischemic pain model rats.

Kwak,  Kyung Hwa; Jung,  Kyung Young; Choi,  Jy Young; Ryu,  Taeha; Yeo,  Jin Seok; Park,  Sung Sik; Lim,  Dong Gun; Kim,  Si Oh; Baek,  Woon Yi; Hong,  Jung Gil

doi:2009.56.4.419

Original Article

Korean Journal of Anesthesiology 2009;56(4):419-424.
DOI: https://doi.org/10.4097/kjae.2009.56.4.419

Contralateral allodynia and central change in the chronic post-ischemic pain model rats.

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

Department of Anesthesiology and Pain Medicine, Kyungpook National University School of Medicine, Daegu, Korea. dglim@mail.knu.ac.kr

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