[Effect of clonidine on rat's behavior response and spinal nitric oxide in formalin test].

OBJECTIVE: To assess the effect of Clonidine on SD rat's behavior response and spinal nitric oxide in the formalin test. METHODS: The effects of Clonidine (Clo), L-arginine(L-Arg), and NG-nitro-L-arginine (L-NAME) on the flinching and licking time of rats in the formalin test were assessed using the model of formalin-induced hyperalgia. RESULTS: The flinching and licking time of group Clo was shorter (38.60 +/- 17.34) s/5 min than that of group Formalin(155.41 +/- 22.04) s/5 min. Pre-administration of L-Arg could potentiate the Clonidine-induced response; pre-administration of L-NAME could reduce the Clonidine-induced response. CONCLUSION: Spinal nitric oxide release might be one of the antinociception mechanisms of Clonidine in the formalin test.