曲马多对切口痛诱发大鼠脊髓背角神经元c-fos基因和血液IL-6表达的抑制作用

目的:在大鼠切口痛模型中研究腹腔注射曲马多对脊髓c-fos蛋白表达和血液IL-6含量的影响.方法:雄性SD大鼠48只,随机分为6组,每组8只,分别为假手术组、切口痛组、术前3个浓度曲马多预处理组(剂量分别为1 mg/kg、10 mg/kg、20 mg/kg)和术后曲马多治疗组(剂量为10 mg/kg).按Brennan法制成大鼠切口痛模型,以von Frey细丝法(机械性痛觉过敏)、热辐射法(热痛觉过敏)和累积疼痛评分法观察疼痛的行为学变化.手术后2 h取脊髓,并以免疫组织化学检测脊髓c-fos表达(Fos蛋白,以FLI阳性神经元表示),ELISA法测定血清IL-6含量.结果:与假手术组比较,在术后2 h时切口痛组大鼠的von Frey纤毛刺激缩爪阈值明显降低(P<0.01),热刺激缩爪潜伏期明显缩短(P<0.01),累积疼痛评分明显升高(P<0.01);与切口痛组比较,曲马多预处理10 mg/kg和20 mg/kg组大鼠的von Frey纤毛刺激缩爪阚值均明显增加(P<0.01),热刺激缩爪潜伏期均明显延长(P<0.01),累积疼痛评分均明显降低(P<0.01),此效应呈剂量依赖性;PT10组大鼠的行为学改变与T10组相似.切口痛组FLI细胞主要分布在Ⅰ～Ⅱ层,曲马多预处理10 mg/kg和20 mg/kg组FLI细胞与切口痛组相比减少.与假手术组比较,切口痛组大鼠脊髓c-fos表达和血液IL-6含量明显增加(P<0.01);与切口痛组比较,曲马多预处理10 mg/kg和20 mg/kg组能使脊髓c-fos表达和血液IL-6含量明显降低(P<0.01),此效应呈剂量依赖性,而术后曲马多治疗组这种抑制作用弱于曲马多预处理10 mg/kg组(P<0.05).与切口痛组比较,曲马多预处理1 mg/kg组的痛阈和脊髓c-fos表达以及血液IL-6含量差异无显著性意义(P>0.05).结论:曲马多能对疼痛引起的脊髓灰质背角FLI阳性神经元增多和血液IL-6含量增加的效应产生剂量依赖性的抑制作用,曲马多预处理效果更强;脊髓灰质背角Ⅰ～Ⅱ层可能是曲马多产生痛觉调制的主要部位.在大鼠切口痛模型中,曲马多的抗伤害作用可能与抑制脊髓c-fos的表达和减少血液IL-6含量有关.

Tramadol inhibits c-fos expression in spinal cord dorsal horn and serum IL-6 levels induced by plantar incision in rats

Objective: To investigate effect of tramadol on c-fos expression in spinal cord dorsal horn and serum IL-6 levels induced by plantar incision in rats. Methods: The Brennan pain model was induced by incision on the planter surface of left hind paw in rats.Forty-eight rats were randomly divided into six groups:Sham group (Group C),control group (Group Ⅰ,pretreatment with saline 5 ml),three tramadol pretreatment groups (Group T1,T10 and T20,pretreated with 1 mg/kg,10 mg/kg and 20 mg/kg tramadol,respectively) and one tramadol treatment group (Group PT10,treated with tramadol 10 mg/kg immediately after operation).Pain behavior was assessed by withdrawal threshold to von Frey filament stimulation intensity,response latency of the hind paw to radiant thermal and a cumulative pain score 2 h after incision.Fos-positive neurons in spinal cord were identified by the immunohistochemical technique.Serum IL-6 levels were measured by enzyme-linked immunosorbent assay (ELISA). Results: Withdrawal threshold to von Frey filament stimulation intensity and response latency of the hind paw to radiant thermal in Group Ⅰ were significantly lower than those in Group C (P<0.01).Cumulative pain score in Group Ⅰ was significantly higher than that in Group C (P<0.01).In Groups of T10 and T20,withdrawal threshold to von Frey filament stimulation intensity and response latency of the hind paw to radiant thermal were significantly higher than those in Group Ⅰ (P<0.01),cumulative pain score was significantly lower than that in Group Ⅰ in a dose-dependent manner (P<0.01),and were also those in Group PT10.The greatest density of Fos-positive neurons was located in lamine Ⅰ-Ⅱ in Group Ⅰ.Serum IL-6 levels were significantly elevated in Group Ⅰ.Pretreatment with tramadol showed a dose-depended inhibitory effect on c-fos expression and serum IL-6 production,but not in Group T1.Administration of tramadol postoperatively also suppressed the c-fos expression and serum IL-6 production as showed in PT10 but were weaker than those in Group T10. Conclusions: Pretreatment with tramadol can produce dose-dependent inhibitory effect on c-fos expression in spinal cord dorsal horn and then suppress the inflammatory response to the trauma.