6-羟基多巴胺损毁大鼠内侧前脑束早期黑质-纹状体系统的铁水平与多巴胺能神经元退变的关系

Correlation between iron levels and degeneration of dopaminergic neurons in rat nigrostriatal system during the early 6-OHDA lesions in medial forebrain bundle

应用快速周期伏安法(fast cyclic voltammetry,FCV)、原子吸收分光光度法及免疫组织化学方法,观察了6-羟基多巴胺(6-hydroxydopamine,6-OHDA)单侧损毁大鼠内侧前脑束(medial forebrain bundle,MFB)早期黑质(substantia nigra,sN)铁水平与多巴胺(dopamine,DA)神经元损伤的变化,以及纹状体(striatum,Str)的DA释放。结果如下:6-OHDA单侧损毁大鼠MFB 1 d和3 d后,SN的酪氨酸羟化酶(tyrosine hydroxylase,TH)阳性细胞分别下降了45％和66％;与正常鼠和未损毁侧相比,损毁侧SN的铁染色增强,铁浓度增加,而Str的DA释放量不变;6-OHDA损毁后1 d与3 d组相比,损毁侧的铁染色、铁浓度及DA释放量差别无显著性。上述结果表明,6-OHDA单侧损毁大鼠MFB的早期阶段,SN中的DA能神经元数目中等程度减少时,铁染色及铁浓度即有增加,由于DA能神经系统有强大的代偿功能,使得Str的DA释放量仍趋于正常。

In the present study, using fast cyclic voltammetry (FCV), atomic absorption/flame emission spectrophotometry and immunohistochemistry, we investigated the correlation between iron levels and degeneration of dopaminergic neurons in rat nigrostriatal system during the early 6-OHDA lesions in the medial forebrain bundle (MFB). The results showed that 1 d or 3 d after lesions in MFB, there was a 45% or 66% reduction, respectively, in the density of tyrosine hydroxylase (TH) immunoreactive cells in the substantia nigra (SN) of the lesioned side accompanied by an increase in iron staining intensity and iron concentration; while there was no change in dopamine (DA) release in the striatum (Str) of the lesioned side compared with the unlesioned side and the normal rats. There was no difference in the iron staining and concentration of SN and DA release of Str on the lesioned side between one-day group and three-days group.These results suggest that an iron level elevation in SN may be involved at the early stage of degeneration of DA neurons in SN. However, DA release in Str was unchanged due to the immense compensatory mechanism of DA system.