Spontaneous regeneration of nigrostriatal dopaminergic neurons in MPTP-treated C57BL/6 mice.

The spontaneous recovery of nigrostriatal dopaminergic neurons was quantitatively analyzed with tyrosine hydroxylase (TH)-immunocytochemistry in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated C57BL/6 young mice. A substantial reduction of striatal dopamine (DA) level was observed until 24 days following MPTP treatment. The TH-immunoreactive (IR) fibers and number of TH-positive cell bodies were also markedly reduced at 3 days after the toxin treatment. Thereafter, TH-IR fiber densities showed to progressively recover through the examining period. The number of TH-positive cell bodies in substantia nigra pars compacta were not changed during the recovery period. These results indicate that MPTP-treated mice have a potential for spontaneous regenerative sprouting in nigrostriatal dopaminergic system.