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KMID : 0311120020430030370
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Yonsei Medical Journal
2002 Volume.43 No. 3 p.370 ~ p.376
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Effects of MK-801 and Morphine on Spinal C-Fos Expression during the Development of Neuropathic Pain
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Youn Woo Lee/Youn Woo Lee
Kyung Ah Park/Won Taek Lee
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Abstract
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The purpose of this study was to investigate the expression of c-fos in the spinal cord during the development of allodynia, induced by peripheral nerve injury. Following tight ligation of the left L5 and L6 spinal nerves of Sprague-Dawley rat, the lumbar spinal cord was postfixed following perfusion. Frontal frozen sections of 40 μm were immunostained according to the peroxidase-antiperoxidase method. The allodynic threshold was checked with 8 calibrated von Frey filaments. MK-801 (0.3 mg/kg), morphine (3 mg/kg) and saline (as a placebo) were administered subcutaneously 30 min before, and 24 and 48 hrs after surgery. The tactile threshold decreased below 3 g since 2 days after surgery in the saline and morphine groups, but delayed a little in the MK-801 group. In the superficial layer the number of Fos-like immunoreactive neurones (Fos-LI) peaked at 2 hours and decreased thereafter, and reached normal levels 24 hrs following operation, for all groups. In the deep layer they were biphasic, - peaking at 2 and 24 hrs - in the saline group, but were suppressed in the morphine and MK-801 groups until 7 days following operation. The above discrepancy between the number of Fos-LI and the allodynic threshold showed that central sensitizations are not critically involved in the development of nerve injury induced tactile allodynia.
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KEYWORD
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Allodynia, central sensitization, spinal c-fos, MK-801, morphine,
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