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KMID : 0356920090570030337
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Korean Journal of Anesthesiology
2009 Volume.57 No. 3 p.337 ~ p.341
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Effect of intrathecal oxcarbazepine on rat tail flick test-determined morphine tolerance
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Jun In-Gu
Park Jong-Yeon
Choi Yun-Sik
Im So-Hyun
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Abstract
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Background: Repeated administration of morphine leads to characteristic tolerance. We tested the effects of intrathecal oxcarbazepine (OXC) on spinal morphine tolerance in rats using the tail flick test.
Methods: Sprague-Dawley rats received intrathecal injections of 10?l saline alone, or 10?l of solutions containing 100?g OXC, 15?g morphine, or OXC ＋ morphine for 7 days. Different groups of rats received OXC on days 1?7, 1?3, or 5?7. The tail-flick assay was used to measure acute and chronic nociception. The nociceptive stimulus consisted of dipping the distal 5 cm of the tail into warm water before and 30 min after drug injection. On day 8, an antinociceptive dose-response curve was plotted, and the 50% effective dose for morphine (given alone) was determined for all groups.
Results: Morphine or OXC both produced acute antinociception; OXC ＋ morphine resulted in a significantly larger response than obtained with morphine alone. Morphine tolerance was produced by intrathecal injection of morphine over 7 days. Co-administration of morphine and OXC completely blocked morphine tolerance, but tolerance developed when OXC injection was stopped, and morphine potency was partially restored by co-administration of OXC in tolerant rats.
Conclusions: The antinociceptive effect of both acute and chronic morphine therapy is increased with intrathecal OXC, and antinociceptive morphine tolerance is attenuated in rats.
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KEYWORD
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Intrathecal, Morphine, Oxcarbazepine, Tail flick test, Tolerance
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