有氧运动改善尼古丁成瘾小鼠中脑腹侧被盖区多巴胺能神经元“去抑制”

Aerobic Exercise Restores Nicotine Addiction Induced Reduction of Inhibitory Synaptic Transmission on VTA Dopamine Neurons

目的:探究有氧运动对尼古丁成瘾形成期中脑腹侧被盖区多巴胺能神经元抑制性突触可塑性的影响。方法:以2月龄雄性SPF级C57BL/6J小鼠为研究对象,随机将小鼠分为安静生理盐水组(sedentary saline,SS)、运动生理盐水组(exercise saline,ES)、安静尼古丁组(sedentary nicotine,SN)和运动尼古丁组(exercise nicotine,EN),ES和EN组小鼠进行8周运动干预;条件性位置偏爱行为学(CPP)实验评价小鼠成瘾行为;免疫荧光染色检测小鼠VTA酪氨酸羟化酶(TH)的表达;脑片膜片钳检测VTA多巴胺能神经元自发性动作电位、sIPSC和mIPSC。结果:(1)有氧运动显著降低尼古丁成瘾小鼠CPP得分(P<0.05);(2)反复使用尼古丁和运动对小鼠VTA多巴胺能神经元基础膜特性无显著性影响(P>0.05);(3)有氧运动降低尼古丁成瘾小鼠VTA多巴胺能神经元自发性动作电位发放频率(P<0.01);(4)有氧运动降低尼古丁成瘾小鼠VTA多巴胺合成限速酶TH的过度表达(P<0.05);(5)有氧运动提高尼古丁成瘾小鼠VTA多巴胺能神经元sIPSC平均频率(P<0.001),提高尼古丁成瘾小鼠急性灌流尼古丁前后VTA多巴胺能神经元sIPSC平均频率的变化幅度(P<0.05),对各组小鼠VTA多巴胺能神经元sIPSC平均幅度无显著性影响(P>0.05);(6)反复使用尼古丁和运动对小鼠VTA多巴胺能神经元mIPSC平均频率和平均幅度均无显著性影响(P>0.05)。结论:8周有氧运动增强尼古丁成瘾小鼠VTA多巴胺能神经元抑制性突触传递效能,降低多巴胺能神经元激活水平,这可能是运动改善尼古丁成瘾的中枢机制之一。

Objective:This research examines whether repeated nicotine exposure alters the inhibitory synaptic transmission on VTA dopamine neurons,and if so,whether exercise affects nicotine-induced changes in the inhibitory synaptic transmission. Methods:2-month-old male SPF C57BL/6J mice were randomly divided into 4 groups:a sedentary saline group(SS),an exercise saline group(ES),a sedentary nicotine group(SN)and an exercise nicotine group(EN). The ES and EN groups were undergoing 8-week exercise training;conditioned place preference behavior(CPP)experiment was used to detect addiction related behavioral changes;immunofluorescence staining was used to detect the expression of tyrosine hydroxylase(TH)in VTA;patch clamp was used to record the electrophysiological indicators of dopaminergic neurons in the VTA:spontaneous action potential,sIPSC and mIPSC.Results:(1)Aerobic exercise significantly reduced the CPP score of nicotine-addicted mice(P<0.05);(2)Repeated use of nicotine and exercise had no significant effect on the basal membrane properties of VTA dopaminergic neurons in mice(P>0.05);(3)Aerobic exercise decreased the frequency of spontaneous action potential firing of VTA dopaminergic neurons in nicotine-addicted mice(P<0.01);(4)Aerobic exercise reduced the overexpression of TH in the VTA of nicotine-addicted mice(P<0.05);(5)Aerobic exercise increased the mean frequency of s IPSC of VTA dopaminergic neurons in nicotine-addicted mice(P<0.001),enhanced the change of the mean frequency of s IPSC induced by acute nicotine perfusion in nicotine-addicted mice(P<0.05),but had no significant effect on the mean amplitude of sIPSC of VTA dopaminergic neurons in each group(P>0.05);(6)Repeated exposure to nicotine and exercise had no significant effect on the mean frequency and mean amplitude of mIPSC in the VTA dopaminergic neurons(P>0.05).Conclusion:Aerobic exercise enhances the inhibitory synaptic transmission on VTA dopaminergic neurons,and decreases the excessive excitability of VTA dopaminergic neurons induced by repeated nicotine exposure,which might be one of the central mechanisms for exercise induced protection against nicotine addiction.