Effects of Intrathecal Amiloride and Its Interaction with Tizanidine on Treatment of Inflammatory Pain in Rats

【Objective】To investigate the effect of intrathecal amiloride and its interaction with tizanidine on the treatment of inflammatory pain in a rat model.【Methods】Ninety-six male SD rats(250～300 g)were randomly divided into sixteen groups(n =6):control group;amiloride group;tizanidine group;amiloride+tizanidine group;and yohimbine group.Seven days after IT catheter placement,50μL of 5%formalin was injected subcutaneously into the dorsal surface of the right hindpaw using 27-gauge needle.Pain-related behavior was quantified by counting the number of flinches.Inhibitory effect(ID50)values and 95% confidence intervals were calculated.Isobolographic analysis of the amiloride and tizanidine interaction was conducted.【Result】Intrathecal amiloride(12.5～100μg)or tizanidine(0.5～5μg)alone produced dose-dependent treatment effect of acute and chronical inflammatory pain.Intrathecal mixtures(tizanidine+amiloride)produced dose-dependent treatment effect of acute and chronic inflammatory pain.Intrathecal pretreatment with yohimbine antagonized the treatment effect of amiloride,tizanidine and the combination of amiloride and tizanidine.【Conclusion】Intrathecal amiloride and tizanidine alone produced dose-dependent treatment effect of inflammatory pain.The enhancing effects were found between intrathecal amiloride and tizanidine.The treatment effect of inflammatory pain produced by intrathecal amiloride may due toα2-adrenoceptor in the spinal.