Objective:To explore whether the activation of extracellular signal-regulated kinases(ERK)signaling in spinal dorsal horn(SDH)neurons participates in DNFB-induced chronic itch sensation.Methods:The ICR male mice,8-12 weeks old,were divided into two groups:DNFB-induced group and acetone control group.The mice in DNFB group were repeatedly smeared with 1.5% DNFB(dissolved by acetone)on the skin of the cheek and the nape to establish the chronic itch model which was analogous to the allergic dermatitis.After DNFB or acetone treatment,the spontaneous scratching behavior was observed and recorded.And the effect of MEK inhibitor U0126 intrathecal injection on the spontaneous scratching behavior was observed.Finally,the perfusion of 4% PFA was performed in mice of DNFB group and control group,the cervical cord segments(C4-C8)were removed,and the expression of pERK was detected by immunofluorescence.Results:In the cheek model,the DNFB-treated mice showed more scratching behavior(86 times in 30 min)than the control mice(17 times in 30 min).In the neck model,compared with the control mice(19 times in 30 min),the DNFB-treated mice showed vigorous scratching behavior(240 times in 30 min).So the chronic neck itch model was successfully established.After the MEK inhibitor U0126 was administered intrathecally at the lumbar level,the scratching behavior of DNFB-treated mice was inhibited obviously.Consistent with the behavior result,the intrathecal injection with U0126 could significantly reduce the number of positive neurons with p-ERK expression at the spinal horn.The activation of pERK was dominantly expressed at lamina Ⅰ andⅡ of spinal horn.In addition,pERK co-expressed with NeuN(a neuron marker),but did not co-expresse with GFAP and Iba1(specific markers for astrocyte and microglia).Conclusions:The phosphorylation of ERK signaling in SDH neurons is required for the regulation of DNFB-induced chronic itch sensation.%目的:探讨脊髓背角细胞外信号调节激酶(extracellular signal-regulated kinase,ERK)磷酸化对2,4-二硝基氟苯(2,4-dinitrofluorobenzene,DNFB)诱导的小鼠慢性痒的调控作用.方法:8~12周ICR雄性小鼠随机分为DNFB诱导组和丙酮对照组.DNFB组小鼠分别于面颊部和背部反复涂抹1.5% DNFB溶液,建立类似特异性皮炎的慢性痒模型.分别观察慢性痒模型建立后小鼠的自发性行为,以及鞘内注射M EK抑制剂U0126后小鼠自发性慢性痒行为的变化.免疫组织化学染色法分析小鼠脊髓组织磷酸化 ERK(phosphrylated ERK,pERK)的表达情况.结果:面颊部诱导模型中,DNFB组小鼠的搔抓次数明显高于丙酮对照组(P<0.05),而擦涂行为无差异,证实DNFB诱发的是痒觉;颈背部诱导模型中,DNFB组小鼠表现出剧烈的搔抓行为,而丙酮对照组的搔抓行为不明显.背部慢性痒模型建立后,分别在第1、3、7和14天鞘内注射 M EK 抑制剂U0126,小鼠的搔抓行为受到明显抑制(P<0.05),且脊髓背角pERK的表达水平也明显降低(P<0.05).pERK活化主要表达于小鼠脊髓背角Ⅰ ~ Ⅱ层,且与神经元标志物NeuN共标,与星形胶质细胞标志物GFAP和小胶质细胞标志物Iba1不共标.结论:脊髓背角浅层神经元 ERK磷酸化可能参与调控DNFB诱导的慢性痒.
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