| Effect of Spinal Adrenergic and Cholinergic Antagonists for Antinociception of Intrathecal Gabapentin. |
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Myung Ha Yoon, Sung Su Chung, Hyeong Seok Kim |
1Department of Anesthesiology and Pain Medicine, Chonnam National University, Gwangju, Korea. mhyoon@chonnam.ac.kr
2Department of Medical School, College of Dentistry, Chonnam National University, Gwangju, Korea.
3Department of Research Institute of Medical Science, Chonnam National University, Gwangju, Korea. |
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| Abstract |
BACKGROUND
Intrathecal gabapentin is effective on nociceptive states evoked by tissue injury. In addition, gabapentin interacts synergistically with clonidine at the spinal level, suggesting that a mechanism of gabapentin may be related to spinal adrenoceptors. However, it has not been established whether this drug is associated with cholinergic receptors. The aim of this study was to examine the role of spinal adrenergic and cholinergic receptors on the antinociceptive action of intrathecal gabapentin.
METHODS
Rats were implanted with lumbar intrathecal catheters. For a nociceptive test, 50nl of 5% formalin solution was injected into the hindpaw. The effect of intrathecal gabapentin, administered 10 min before the formalin injection, was assessed. Next, antagonistic effects of intrathecal prazosin, yohimbine, atropine and mecamylamine for the action of intrathecal gabapentin were evaluated.
RESULTS
Formalin injection caused a biphasic incidence of flinching of the injected paw. Intrathecal gabapentin produced a dose-dependent suppression of only the phase 2 flinching response in the formalin test. Intrathecal atropine, but not prazosin, yohimbine nor mecamylamine, reversed the antinociception of intrathecal gabapentin.
CONCLUSIONS
The antinociceptive effect of intrathecal gabapentin on facilitated states may be mediated through the muscarinic receptor but by neither the nicotinic receptor nor the adrenergic receptor at the spinal level. |
| Key Words:
Adrenergic receptor; cholinergic receptor; gabapentin; nociception; spinal cord |
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