Functional changes in cocultures of mesencephalon and striatal neurons from embryonic C57/BL6 mice due to low concentrations of 1-Methyl-4-Phenylpyridinium (MPP+)

Abstract

1-Methyl-4-phenylpyridinium (MPP⁺), the active metabolite of 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is taken up into dopaminergic terminals and selectively destroys dopaminergic neurons, serving as a valuable tool in animal model of Parkinson's disease. Cocultures from ventral mesencephalon and neostriatum of embryonic C57/BL6 mouse brains were used to study the sensitivity of dopaminergic neurons to the toxic agent MPP⁺. Cultures were grown for 9 days in vitro and exposed to different concentrations of MPP⁺ for various times. Treatment with (0.1–1.0 μM) MPP⁺ for 24 hours decreased³H-dopamine (³H-DA) uptake with an IC₅₀ at 0.2 μM. Exposure of cells to 1 μM MPP⁺ over time decreased the⁺H-DA uptake to 38% of controls within the first two hours of incubation and to 8% after 48 hours. Loss of tyrosine hydroxylase (TH) positive cells became evident at 0.1 μM MPP⁺ (80% of control) leading to maximal toxicity at 10 μM (20% of control). MPP⁺ reduced the dopamine content in the cultures in a dose dependent manner (IC₅₀ at 0.1 μM) and failed to show reversibility in recovery studies. These findings provide evidence that exposure of MPP⁺ even at low concentrations and for short time in our coculture model results in irreversible toxicity for dopaminergic neurons.