Difference in recovery patterns of striatal dopamine content, tyrosine hydroxylase activity and total biopterin content after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration: a comparison of young and older mice.

Striatal dopamine (DA) content, tyrosine hydroxylase (TH) activity, and total biopterin content were measured as parameters of recovery, after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in 7-week-old (young) and 28-week-old (older) C57 BL/6 mice. After 10 consecutive days of injection of MPTP (30 mg/kg/day) young mice were sacrificed at one day and 2, 4, 8, 12 and 20 weeks; older mice (20 mg/kg/day) at one day and 4, 8, and 12 weeks. All 3 parameters were markedly reduced one day after the last injection of MPTP. During the observation period, the parameters showed a gradual and partial recovery. The recovery rates of the 3 parameters differed significantly, especially during the early phases of 2-8 weeks. Total biopterin content showed a greater rate of recovery than TH activity and TH activity, a greater rate of recovery than DA content. In the older mice group, the recovery of all 3 parameters was retarded significantly, and dissociation of the recovery rates between the 3 parameters was more prominent. The results of our present study suggest that, following neurotoxic injury, the recovery of biopterin may play a significant role in dopaminergic terminal regeneration.