Modeling a sensitization stage and a precipitation stage for Parkinson's disease using prenatal and postnatal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration

Abstract

Idiopathic Parkinson's disease (PD) is a neurodegenerative disorder of mature and older individuals. Since all aged individuals do not develop PD, predisposing conditions may exist that pair with the stress placed on the basal ganglia during aging to produce the symptoms of PD. In this project we used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to test the hypothesis that a sensitization stage and a precipitating stage underlie idiopathic PD. To induce the sensitization stage, pregnant C57BL/6J mice were treated with MPTP (10 mg/kg/day) during gestation days 8–12 to target the emerging fetal nigrostriatal dopamine neurons. For the precipitating stage, the 3-months old offspring were administered MPTP for 7 days, to simulate the changes that occur during aging. The weights and motor activity of the offspring, high performance liquid chromatography (HPLC) striatal dopamine and its metabolites and Western blot for tyrosine hydroxylase (TH) were determined. Offspring exposed to prenatal MPTP showed lower birth weights that eventually recovered. Prenatal MPTP also reduced motor activity by 10–30%, striatal TH by 38%, dopamine by 14%, homovanillic acid by 16.5% and 3-methoxytyramine by 66%. The postnatal MPTP was more potent in the prenatal MPTP-exposed offspring. MPTP at 10, 20 and 30 mg/kg, dose-relatedly, reduced striatal TH by 9.4%, 48.6% and 82.4% in the prenatal-phosphate buffered saline (PBS) mice and by 48%, 78.7% and 92.7% in the prenatal-MPTP groups. More importantly, postnatal MPTP at 10 mg/kg that showed slight effects on DA, DOPAC, HVA and 3-MT in the prenatal-PBS offspring, showed 69.9%, 80.0%, 48.4% and 65.4% reductions in the prenatal-MPTP mice. The study may identify a new model for PD, and the outcome suggests that some cases of idiopathic PD may have a fetal basis in which early subtle nigrostriatal impairments occurred and PD symptoms are precipitated later by deteriorating changes in the nigrostriatum, that would not caused symptoms in individuals with normal nigrostriatal system.