氯胺酮对甲醛致炎性痛小鼠背根节TrkA受体表达的影响

Effect of ketamine on the expression of TrkA receptor in dorsal root ganglion in mice with formalin-induced inflammatory pain

目的:观察N-甲基-D-天冬氨酸受体非特异性拮抗剂氯胺酮对甲醛致炎小鼠疼痛行为学的影响,以及背根节神经生长因子受体TrkA表达的变化。方法:实验于2005-02/05在华中科技大学同济医学院附属同济医院进行。取成年健康昆明种小鼠24只,随机分为正常对照组、甲醛组和甲醛+氯胺酮组3组,每组8只。分别于甲醛组和甲醛+氯胺酮组小鼠右后足底注入体积分数为0.05的甲醛100μL形成急性炎性痛模型,甲醛+氯胺酮组小鼠在注入甲醛后立即经腹腔注入40mg/kg的氯胺酮。正常对照组小鼠不干预。观察甲醛注射后小鼠疼痛行为学变化,甲醛致炎2h后处死小鼠,免疫组化ABC方法检测背根节TrkA受体表达。结果:经补充后24只小鼠进入结果分析。①疼痛行为学变化:甲醛注射后1h内小鼠均出现明显的摔腿、舔足、跛行、致炎足不能着地等疼痛行为学改变,注射足呈高度肿胀。甲醛+氯胺酮组小鼠氯胺酮注射后翻正反射立即消失,甲醛致炎后第一时相(注射后0～5min)、第二时相(注射后20～60min)的疼痛行为学反应次数显著少于甲醛组眼(6.0±2.5),(113.0±9.5)次;(3±0),(75.0±4.5)次;P<0.01演。②背根节TrkA受体阳性神经元平均灰度值:注射侧甲醛组高于甲醛+氯胺酮组和正常对照组(205.3±11.9,121.6±7.9,116.5±7.7,P<0.01),甲醛+氯胺酮组和正常对照组比差异不显著(P>0.05)。结论:氯胺酮能抑制急性炎性痛时疼痛行为学变化,并减少背根节TrkA受体的表达,这种效应可能与TrkA受体下调后初级伤害性刺激传入减少有关。

AIM： To explore the effect of N-methyl-D-aspartate, non-specific antagonist ketamine on behavior changes of mice with inflammatory pain due to formalin and the changes of TrkA expression of nerve growth factor receptor of dorsal root ganglion. METHODS： The experiment was conducted at the Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology from February to May 2005. Twenty-four adult health Qunming mice were selected and randomly divided into normal control group, formalin group and formalin＋ketamine group with 8 mice in each group. 100 μL formalin of the volume fraction of 0.05 was injected into right hindfoot of mice in the formalin group and the formalin＋ketamine group, respectively to establish acute inflammatory pain models. The mice in the formalin＋ketamine group were injected with 40 mg/kg ketamine through abdominal cavity immediately after injecting with formaldehyde. The mice in the normal control group were not interfered. The changes in the behavior of inflammatory pain mice following the injection of formalin were observed. The mice were killed two hours after formalin-induced inflammation. Expression of TrkA receptor of dorsal root was detected with immunohistochemical ABC method. RESULTS： A total of 24 mice were involved in the result analysis after compensation.①Changes of behavior in mice with inflammatory pain： After injecting for 1 hour the mice showed significant nociceptive behavior： throwing leg, licking foot, limping, and the inflammatory foot could not touch the ground. The injected foot was swelling highly. Righting reflex disappeared immediately after injecting with ketamine in the mice of the formalin＋ketamine group. The reaction number of pain behavior at the first time phase （0-5 minutes after injection） and second time phase （20-60 minutes after injection） after inducing inflammation was less obviously than that in the formalin group [（6.0±2.5）,（113.0±9.5） times; （3±0）,（75.0±4.5） times;P〈 0.01].②Mean gray value of positive neuron of TrkA receptor of dorsal root： It was higher in the injected side of the formalin group than that in the formalin＋ketamine group and the normal control group （205.3±11.9,121.6±7.9,116.5±7.7,P 〈 0.01）. The difference was insignificant between the formalin＋ketamine group and the normal control group （P 〉 0.05）. CONCLUSION： Ketamine can inhibit the nociceptive behavior and reduce the TrkA expression in dorsal root ganglion following acute inflammatory pain, and this effect may be related to the reduced primary nociceptive afferent stimulation from the down-regulated TrkA receptor to the spinal dorsal horn.