| The effect of inducing morphine tolerance on anti-allodynic action of gabapentin in spinal nerve-ligated rat. |
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Jin Hua Cui, Hyung Gon Lee, Woong Mo Kim, Hong Beom Bae, Myung Ha Yoon, Jeong Il Choi |
1Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju, Korea. aneszzz@naver.com
2Department of Medicine, Chonnam National University Graduate School, Gwangju, Korea. |
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| Abstract |
BACKGROUND
Morphine is more effective in inflammatory or acute pain than neuropathic pain. Recently, some reports demonstrated that the development and maintenance of opioid tolerance and neuropathic pain have similar aspects. Here, we evaluated whether morphine tolerance affects the anti-allodynic effect of gabapentin in spinal-nerve ligated rat.
METHODS
Male Sprague-Dawley rats weighing 100-120 g received L5,6 spinal nerve ligation to induce neuropathic pain. Rats showing allodynia were implanted with intrathecal (i.t.) catheter to administer the experimental drugs into the subarachnoid space. To induce olerance to morphine, 15 microgram of morphine was injected via i.t. catheter twice a day for 7 days, and the effect of i.t. gabapentin on the paw withdrawal threshold was examined using the von Frey test before and after the development of morphine tolerance.
RESULTS
Ligation of spinal nerves decreased the paw withdrawal threshold. Intrathecal morphine initially increased the paw withdrawal threshold, but this effect decreased gradually over time. However, morphine tolerance did not influence the effect of gabapentin on withdrawal threshold.
CONCLUSIONS
Morphine tolerance did not affect gabapentin efficacay in a neuropathic pain model. |
| Key Words:
Antiallodynia; Gabapentin; Morphine; Neuropathic pain; Tolerance |
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