老年大鼠黑质致密部多巴胺能神经元的变化

Changes of dopaminergic neurons in substantia nigra compact of the aged rats

目的探讨老年大鼠黑质致密部多巴胺(DA)能神经元的变化。方法采用逆转录PCR(RT-PCR)、免疫印迹法、免疫组化染色和电镜技术,观察老年大鼠(≥24月龄)黑质致密部DA能神经元酪氨酸羟化酶(TH)mRNA、蛋白表达水平和TH阳性神经元数及其超微结构,并与成年大鼠(4～5月龄)比较。结果老年组大鼠黑质致密部THmRNA水平(0.66±0.12)明显低于成年组(1.09±0.08)(P<0.05);TH蛋白水平及TH阳性神经元数与成年组差异均无统计学意义(均P>0.05);老年组大鼠黑质致密部尾侧段TH阳性神经元数比成年组明显减少(P<0.05),其超微结构显示细胞器少、脂褐素多、核固缩、线粒体形态异常且数量减少。结论老年大鼠黑质致密部DA能神经元THmRNA水平下降,尾侧DA能神经元明显减少,并呈衰老性改变,这可能是老年黑质纹状体功能降低的生物学基础。

Objective To investigate the changes of dopaminergic （DA） neurons in substantia nigra compact of the aged rats. Methods Using RT-PCR, Western blot, immunohistochemistry and electron microscope to detect the levels of TH mRNA and TH protein, the number and the ultrastructure of TH-positive neurons in the substantia nigra compact of the aged rats（≥24 months）, and comparing those with adult rats（4 -5 months）. Results The level of TH mRNA （0.66 ±0.12） in substantia nigra compact of the aged rats was much lower than that in the adult rats （ 1.09 ± 0. 08 ） （ P 〈 0. 05 ）, but there were no differences for the level of TH protein and the number of TH-positive neurons in substantia nigra compact between the aged rats and the adult rats （ all P 〉 0.05 ）. However, the number of TH-positive neurons in the caudal of substantia nigra compact of the aged rats was much lower than that of the adult rats （P 〈 0. 05 ）, and the ultrastructure of them showed the fewer of cell organs, the more lipofuscins, the pyknosis of cellular nucleus, the paramorphia and the fewer of mitochondria. Conclusions The decrease of TH mRNA in substantia nigra compact of aged rats, and the selectivity decrease of dopamine neurons, as well as the aging change in the caudal of substantia nigra compact aged rats, may have important implication for the biology cause of the degraded function of the aging nigrostriatal dopaminergic system in this region.