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KMID : 0811720010050000174
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Korean Journal of Physiology & Pharmacology
2001 Volume.5 No. 0 p.174 ~ p.0
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Effect of Morphine on the Mechanical Allodynia in Spinal Hemisectioned Rat
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Kim June-Sun
Jung Ji-In
Hong Seung-Kil
Na Heung-Sik
Yoon Young-Wook
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Abstract
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Spinal cord injury may lead to various kinds of pain including musculoskeletal, visceral, neuropathic at level and neuropathic below level pain. In general, neuropathic pain is characterized by the occurrence of spontaneous pain as well as evoked pain and is perceived to be resistant to treatment with opioids. The aim of this study was to observe whether morphine reduces the behavioral signs of neuropathic pain below level in the spinal hemisection model. Spinal cord injury was made by hemisection of spinal cord at T13 level in Sprague-Dawley rats under enflurane anesthesia. Changes of 50% threshold of hindlimb withdrawal to mechanical stimulation applied to the plantar surface were measured. In order to examine the effect of morphine on the mechanical allodynia, morphine alone (2 and 5 mg/kg), morphine with naloxone and saline were injected intraperitoneally and behavioral tests were conducted. Mechanical allodynia was well developed in both hindlimbs. Mechanical allodynia was reduced only when higher concentration of morphine (5 mg/kg) was used. Pain reducing effect of morphine was more pronounced in the ipsilateral hindlimb. Simultaneous injection of naloxone blocked the effects of morphine. Lower dose or saline did not change the mechanical allodynia. The data show that mechanical allodynia following spinal hemisection is generally resistant to morphine. Difference in response to morphine in ipsi- and contralateral limb suggests that the mechanisms of mechanical allodynia in both limb may be different even though the magnitude of allodynia is apparently similar.
Source: Korean J Physiol Pharmacol.2001 Dec;5(Suppl II):S97-S98
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