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KMID : 0811720030070000187
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Korean Journal of Physiology & Pharmacology
2003 Volume.7 No. 0 p.187 ~ p.0
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Mechanical and Cold Allodynia Produced by Spinal Cord Contusion Is Not Mediated by Vanilloid-Sensitive Afferent Fibers
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Jung Ji-In
Lee Sun-Ho
Kim June-Sun
Hong Seung-Kil
Yoon Young-Wook
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Abstract
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Spinal cord injury frequently results in the central neuropathic pain which is refractory to the conventional analgesic treatments. The mechanisms of neuropathic pain are still poorly understood. Resiniferatoxin (RTX) is a potent capsaicin analog. It binds to vanilloid receptors then can cause vanilloid-sensitive neuronal cell death. The aim of this study is to observe whether vanilloid-sensitive afferent fibers can mediate mechanical allodynia and cold allodynia in spinal contused rats.
The spinal cord was contused at T12 level using the NYU impactor in Sprague-Dawley rats (n=32) anesthetized with pentobarbital. Changes of 50% threshold of hindlimb withdrawal to mechanical stimulation applied to the plantar surface and frequency of foot withdrawal to acetone application were measured. Paw withdrawal and tail flick latencies to radiant heat were measured. Motor function was examined using CBS score. Subcutaneous RTX injection (0.3 mg/kg) was performed at days 21 P.O.
Mechanical and cold allodynia was well developed in both hindlimbs following spinal contusion. Paw withdrawal and tail flick latencies were prolonged by RTX injection but RTX could not change mechanical allodynia and cold allodynia. Motor function was not affected by RTX injection. It is suggested that capsaicin sensitive afferent fibers do not carry below level pain such as mmechanical and cold allodynia.
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KEYWORD
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Allodynia, Spinal cord injury, Resiniferatoxin
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