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

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)(P0.05),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 P0.05).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(P0.05),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.