MPTP对快速老化小鼠黑质纹状体系统的急性损害及小胶质细胞的激活

Acute damage of nigrostriatal system in MPTP-treated senescence accelerated mouse and damage-related microglial activation

目的:探讨MPTP(1-甲基-4-苯基-1,2,3,6-四氢吡啶)对快速老化小鼠(senescence accelerated mouse prone8,SAMP-8)黑质纹状体系统的急性损害及小胶质细胞激活与损害的关系。方法:57只健康雄性12周龄SAMP8小鼠,随机分为生理盐水对照组和MPTP组,每组再分别于第1次给药后6h、24h、3d和8d四个时间点处死小鼠,每个时间点6～9只。SAMP8小鼠背部皮下注射MPTP20mg·kg-1,1次/2h,注射4次,观察各时间点小鼠的自主活动;免疫组织化学染色检测各时间点黑质TH+神经元数量、纹状体TH免疫反应性及小胶质细胞的状态;HPLC技术检测纹状体DA含量。结果:第3次注射后小鼠出现明显活动减少,并于第1次给药后48h恢复近正常水平。与对照组相比:MPTP组黑质TH+神经元数目于第1次注射后6h、24h、3d、8d分别减少7.06%(P=0.235)、12.79%(P<0.05)、22.49%(P<0.01)、42.39%(P<0.001),两个时间点之间比较3d与8d有统计学差异(P<0.05);与对照组相比,MPTP组纹状体TH免疫反应性(COD值)减低,6h(P<0.05)、24h(P<0.01)、3d(P<0.001)、8d(P<0.001),两个时间点之间比较24h与3d比较差异有统计学意义(P<0.05);纹状体多巴胺含量6h降低79.09%(P<0.001),24h降低80.3%(P<0.001),3d降低86.6%(P<0.001),8d降低81.0%(P<0.001),但24h、3d、8d比较无统计学差异。纹状体小胶质细胞于给药后24h免疫反应性明显增强,3d明显激活,8d激活现象明显回落。结论:MPTP可导致SAMP8小鼠黑质纹状体系统的急性损害,出现自主活动减少、黑质多巴胺能神经元减少及纹状体多巴胺能纤维脱失,多巴胺含量降低;小胶质细胞激活可能与MPTP-SAMP8小鼠的黑质纹状体系统损伤有关。

Objective： To investigate the acute damage of the nigrastriatal system in SAMP8 mouse after treatment with MPTP and its relationship with microglial activation. Methods： Totally 57 male SAMP8 mice were randomly divided into two groups,control group and MPTP group. Mice were sacrificed （each time 6-9 mice） at 6 h, 24 h, 3 d,and 8 d after the first injection in each group. Mice were subcutaneously injected with normal saline or MPTP （20 mg/kg） at an interval of 2 h for 4 times. The changes of spontaneous activity of mice were observed after injection. The changes of TH＋ （tyrosine hydroxylase positive） neuronal numbers in the substantial nigra,TH-ir （tyrosine hydroxylase immunoreactivity）, and microglial activation in striatum were examined by immunohistochemistry; striatal dopamine （DA） levels were determined by HPLC. Results： The spontaneous activity of SAMP8 mice was decreased significantly after the third injection, and recovered at 48 h after the first injection. Compared with the control group,the TH^＋ neurons in MPTP group decreased by 7.06% at 6 hours （P=0. 235） ,by 12.79% at 24 hours（P〈0.05） ,by 22.49% at 3 days（P〈0.01） ,and by 42. 39% at 8 days（P〈0. 001） ; there was significant difference in the TH＋ neurons between the 3 days and 8 days （P〈0.05）. The corrected optical densities （COD） of TH-ir in the striatum in MPTP group were significantly lower than those in the control group at different time points （6 h,[P〈0.05],24 h [P〈0.01],3 d[P〈0. 001] ,8 d[P〈0. 001]） ; there was significant difference between the 24 h and 3 days groups （P〈0.05）.Compared with the control group,the striatal dopamine （DA） levels decreased by 79. 09% at 6 hours （ P〈0. 001） ,by 80.3% at 24 hours （P〈0. 001）,by 86. 6% at 3 days （P〈0. 001）,and by 81.0% at 8 days （P〈0. 001）; there were no significant difference between the 24 h, 3 days, and 8 days. The immunoreactivity of microglial greatly increased at 24 hours, further activated at 3 days,and largely abated at 8 days after MPTP injection. Conchtsion： MPTP can cause acute damage to substantia nigra of SAMP8 mice, resulting in reduced spontaneous activity and dopaminergie neurons loss; the activation of mieroglial might be related to the nigrostriatum damage of MPTP-SAMP8 mice.