mTOR在炎性痛大鼠内嗅区-海马结构突触可塑性中的作用

Role of mammalian target of rapamycin in synaptic plasticity of entorhinal area-hippocampal formation in rats with inflammatory pain

目的评价哺乳动物雷帕霉素靶蛋白(mTOR)在炎性痛大鼠内嗅区-海马结构突触可塑性中的作用。方法健康成年雄性SD大鼠24只,体重180~240g,采用随机数字表法分为4组(n=6):对照组(C组)、炎性痛组(IP组)、二甲基亚砜组(DMSO组)和mTOR抑制剂雷帕霉素组(R组)。采用左侧后肢足底皮下注射蜜蜂毒溶液50μl方法制备炎性痛模型。C组左侧后肢足底皮下注射生理盐水,二甲基亚砜组给予2%二甲基亚砜灌胃3d,1ml/d,于第3天灌胃后1h时制备炎性痛模型;R组给予雷帕霉素灌胃3d,1ml/d,于第3天灌胃后1h时制备炎性痛模型。于造模后2h时,测定机械缩足反应阈(MWT)和热缩足潜伏期(TWL)。痛阈测定结束后,处死大鼠制备海马脑片,倒置显微镜下定位出CA1区和齿状回(DG区),采用平面微电极阵列技术记录不同刺激强度下诱发有效兴奋性突触后电位(fEPSPs)(fEPSPs幅度>基础值的20%)的通道数和标准化fEPSP幅度。结果与C组比较,IP组MWT降低,TWL缩短,不同刺激强度下有效fEPSPs通道数增加,DG区和CA1区标准化fEPSP幅度升高(P<0.05或0.01),R组上述指标差异无统计学意义(P>0.05);与IP组比较,R组MWT升高,TWL延长,不同刺激强度下有效fEPSPs通道数减少,DG区和CA1区标准化fEPSP幅度降低(P<0.05或0.01),DMSO组上述指标差异无统计学意义(P>0.05)。结论mTOR参与了炎性痛大鼠内嗅区-海马结构突触可塑性的改变。

Objective To evaluate the role of mammalian target of rapamycin(mTOR)in the synaptic plasticity of entorhinal area-hippocampal formation in rats with inflammatory pain.Methods Twenty-four healthy adult male Sprague-Dawley rats,weighing 180-240 g,were divided into 4 groups(n=6 each)by using a random number table method:control group(group C),inflammatory pain group(group IP),dimethyl sulfoxide(DMSO)group and mTOR inhibitor rapamycin group(group R).Inflammatory pain model was established by subcutaneous injection of 50 μl bee venom into the plantar surface of the left hindpaw.The equal volume of normal saline was subcutaneously injected into the plantar surface of the left hindpaw in group C.In group DMSO,2% DMSO was administered by intragastric gavage for 3 days,1 ml per day,and the inflammatory pain model was established at 1 h after administration on 3rd day.In group R,rapamycin was administered by intragastric gavage for 3 days,1 ml per day,and the inflammatory pain model was established at 1 h after administration on 3rd day.Mechanical paw withdrawal threshold(MWT)and thermal paw withdrawal latency(TWL)were measured at 2 h after establishing the model.The rats were sacrificed after measurement of the pain threshold,and hippocampi were removed to prepare hippocampal slices.Hippocampal CA1 region and dentate gyrus(DG region)were located with an inverted microscope.Planar microelectrode array technique was used to record the number of channels and the standardized amplitude of evoked effective field excitatory postsynaptic potentials(fEPSPs)(fEPSPs amplitude>20% of the baseline value)at different stimulus intensities.Results Compared with group C,MWT was significantly decreased,TWL was shortened,the number of effective fEPSP channels at different stimulus intensities was increased,and the amplitude of standardized fEPSPs in hippocampal DG and CA1 regions was increased in group IP(P<0.05 or 0.01),and no significant change was found in the parameters mentioned above in group R(P>0.05).Compared with group IP,MWT was significantly increased,TWL was prolonged,the number of effective fEPSP channels at different stimulus intensities was decreased,and the amplitude of standardized fEPSPs in hippocampal DG and CA1 regions was decreased in group R(P<0.05 or 0.01),and no significant change was found in the parameters mentioned above in group DMSO(P>0.05).Conclusion mTOR is involved in the changes in the synaptic plasticity of entorhinal area-hippocampal formation in rats with inflammatory pain.