有氧运动对尼古丁戒断小鼠VTA多巴胺神经元抑制性突触传递效能的影响

Effects of aerobic exercise on inhibitory synaptic transmission in ventral tegmental area dopamine neurons of mice with nicotine withdrawal

目的探究中等强度有氧运动对尼古丁戒断小鼠VTA多巴胺神经元抑制性突触可塑性的影响,以期为运动减少尼古丁复吸提供一定的实验依据。方法8周龄雄性C57BL/6小鼠随机分为生理盐水安静组(SS组)、生理盐水运动组(SE组)、尼古丁安静戒断组(NS组)、尼古丁运动戒断组(NE组),采用条件性位置偏爱实验建立小鼠尼古丁成瘾模型。之后停止给药,SE组和NE组小鼠进行连续2周的中等强度有氧运动干预,SS组和NS组小鼠自由饮食及进水。采用条件性位置偏爱实验检测小鼠尼古丁复吸行为。使用全细胞膜片钳技术记录VTA多巴胺神经元的自发抑制性突触后电流(sIPSC)、微小抑制性突触后电流(mIPSC)和抑制性突触后电流配对脉冲比(IPSC PPR)。使用免疫荧光染色检测VTAγ-氨基丁酸限速酶GAD67的表达。结果(1)NS组CPP得分高于SS组,NE组CPP得分低于NS组;(2)NS组sIPSC的平均频率和平均幅度高于SS组,NE组sIPSC的平均频率和平均幅度低于NS组;(3)NS组mIPSC的平均频率和平均幅度高于SS组,NE组mIPSC的平均频率和平均幅度低于NS组;(4)20 ms和50 ms刺激间隔时,NS组的IPSC PPR小于SS组,NE组的IPSC PPR大于NS组;(5)NS组VTA GAD67蛋白表达低于SS组,NE组VTA GAD67蛋白表达高于NS组。结论2周的中等强度有氧运动减少尼古丁戒断模型VTA多巴胺神经元突触前GABA释放,下调突触后GABAA受体的数量和/或功能,减弱抑制性突触传递效能,这可能是有氧运动减少尼古丁复吸的机制之一。

Objective To investigate the effects of aerobic exercise on the inhibitory synaptic plasticity of the ventral tegmental area(VTA)dopamine neurons of mice with nicotine withdrawal.Methods Eight-week-old male C57BL/6 mice were randomly divided into a saline sedentary(SS)group,saline exercise(SE)group,nicotine sedentary(NS)group,and nicotine exercise(NE)group following the conditioned place preference(CPP)paradigm.During abstinence,SE and NE group mice were subjected to a moderate-intensity treadmill running protocol for 2 weeks.The CPP paradigm was used to test nicotine-seeking behavior of mice after nicotine withdrawal.The whole-cell patch clamp was used to record the spontaneous inhibitory postsynaptic current(sIPSC),the miniature IPSC(mIPSC),and the IPSC paired-pulse ratio(PPR)of dopamine neurons in the VTA.Immunofluorescence staining was used to detect the expression of GAD67 in the VTA.Results(1)The CPP score was higher in the NS than SS group and lower in the NE than NS group.(2)The mean frequency and amplitude of the sIPSC were higher in the NS than SS group and lower in the NE than NS group.(3)The mean frequency and amplitude of the mIPSC were higher in the NS than SS group and lower in the NE than NS group.(4)At the 20 ms and 50 ms interstimulus intervals,the IPSC PPR was lower in the NS than SS group and higher in the NE than NS group.(5)The fluorescence intensity of GAD67 was lower in the NS than SS group and higher in the NE than NS group.Conclusions 2 weeks moderate intensity aerobic exercise reduces presynaptic GABA release,down-regulates the number and/or function of postsynaptic GABAA receptors in VTA dopamine neurons,and these decreased inhibitory synaptic transmission may represent a potential mechanism by which aerobic exercise attenuates nicotine seeking during abstinence.