Comparison between 2‐day and 10‐day MPTP treatment modalities in the mouse model of Parkinson's disease

We employed a novel regimen of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment to produce a Parkinson's disease (PD) animal model demonstrating typical Parkinsonian symptoms. In order to compare the effects of the different durations of MPTP treatment (daily intraperitoneal injections of 30 mg/kg MPTP for 2 or 10 days), the numbers and distribution patterns of tyrosine hydroxylase-immunoreactive (TH-ir) neurons and fibers were examined in the substantia nigral and stiatal brain regions of C57/B16 mice. The mean numbers of TH-ir neurons in the substantia nigra were significantly lower (57.3% and 48.1%) than the numbers in the saline-treated controls after 2 and 10 days of MPTP treatment, respectively. Furthermore, the optical density of the TH-ir fibers in the striatum was reduced by 9.8% and 14.1% after 2- and 10-day treatments, respectively. However, the reduction in numbers of TH-ir neurons in the substantia nigra and striatum was not significantly different between the 2-day and 10-day treatment groups. Yet, it seems that only the 10-day treatment regimen exceeded the threshold of motor deficits. Thus, chronic MPTP treatment appears to be required to mirror the pathophysiological characteristics of Parkinsonism.