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KMID : 0614520040140010081
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Journal of the Korean Pain Research Society
2004 Volume.14 No. 1 p.81 ~ p.87
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Analgesic Effects of Adenosine Subtype Agonists for Formalin-induced Pain in the Spinal Cord of Rat
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Yoon Myung-Ha
Bae Hong-Beom
Park Hun-Chang
Choi Jeong-Il
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Abstract
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Background: Adenosine has shown the analgesia, which was mediated through spinal adenosine receptors. The presence of four subtypes of adenosine receptors like A1, A2A, A2B and A3 in the spinal cord has been demonstrated. The authors determined the role of spinal adenosine receptors for the nociceptive modulation by examination of effect of intrathecal adenosine subtype agonists for formalin-induced pain.
Methods: Lumbar intrathecal catheterization was done with male Sprague-Dawley rats. Formalin- induced pain developed with injection of formalin solution (5%, 50μl) into the hindpaw of rats. Adenosine subtype agonists (A1, CPA; A2A, DPMA; A3, IB-MECA) were intrathecally given 10 min before the formalin injection. Afnd then, formalin-induced pain behavior (flinching response) was observed for 60 min.
Results: Intrathecal CPA and IB-MECA produced a minimal or no effect during phase 1 response of the formalin test, respectively, but both agents reduced the phase 2 flinching response. Intrathecal DPMA suppressed both phase responses evoked by formalin injection.
Conclusions: Spinal A1 and A2A receptors may play an important role in the modulation of the facilitated state as well as acute nociception and, while A3 receptor being relevant to the modulation of only the facilitated state.
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KEYWORD
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Adenosine, Adenosine receptor subtype, Formalin test, Intrathecal, Rat
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