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KMID : 0811720020060000171
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Korean Journal of Physiology & Pharmacology
2002 Volume.6 No. 0 p.171 ~ p.0
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Systemic and Intrathecal Administration of an NMDA or a non-NMDA Receptor Antagonist Reduces Mechanical and Cold Allodynia in a Rodent Model of Chronic Central Pain after Spinal Cord Injury
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Jung Ji-In
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. It has been reported that the excitatory amino acids are closely related to the central pain mechanisms, but this mechanism is still unknown. The present study was performed to know whether NMDA or non-NMDA receptors are important to central pain after SCI.
The spinal cord was contused at T13 level using the NYU impactor in Sprague-Dawley rats (180-200 g) 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. Motor function was examined using a modification of the combined behavioral score. To evaluate the effects of systemically and intrathecally administered excitatory amino acid receptor antagonists on neuropathic pain, the non-competitive NMDA recepor antagonists dextromethorphan (10, 20, 40 mg/kg) or MK-801 (0.1, 0.25 mg/kg), a competitive NMDA antagonist CGS 19755 (10, 20 mg/kg) and a competitive antagonist of AMPA receptor NBQX (10, 20 mg/kg) were injected peritoneally. Systemic MK-801, dextromethorphan, and NBQX relieved mechanical allodynia and cold allodynia. CGS 19755 caused severe motor deficits at analgesic dose. Intrathecally administered MK-801 and dextromethorphan reduced mechanical allodynia. Systemic MK-801 only induced mild motor impairment at analgesic dose.
The data show that mechanical and cold allodynia can be reduced by both NMDA and non-NMDA antagonists. It is suggested that both NMDA and non-NMDA receptors may play a role for development of central neuropathic pain after spinal cord injury.
Source: Korean Journal of Physiology & Pharmacology.2002 Oct;6(Suppl II):S115-S115
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KEYWORD
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NMDA, AMPA, mechanical allodynia, cold allodynia, spinal cord contusion injury, rat
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