A new in vitro approach for investigating the MPTP effect on DA uptake.
Previous studies have shown that dopamine (DA) uptake was decreased after preincubation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP(+)) in in vitro slice and synaptosome models. The present study, conducted with and without preincubation, attempted to determine whether inhibition results from a direct effect of neurotoxins on neuronal DA transporter or from an alteration of the transporter secondary to other toxic events. DA uptake was inhibited about 50% in the presence of MPTP+O(2) or MPP(+) (0.1, 1 and 5 mM) in rat striatal slices and synaptosomes. Such inhibition was obtained in synaptosomes preincubated for 150 min with MPP(+) and then washed. Inhibition of DA uptake was lower in slices preincubated with MPTP (5 mM)+O(2) and then washed (30%). Experiments in synaptosomes prepared from slices preincubated with MPTP or MPP(+) showed greater inhibition of DA uptake with MPTP. The results suggest that the inhibition of DA uptake in vitro by MPTP or MPP(+) results initially from a direct effect on the transporter during its penetration in nerve endings and subsequently from a transporter alteration related to toxic events. Thus, the preincubation of striatal slices followed by DA uptake measurement in synaptosomes would appear to be a good in vitro model for studying the dopaminergic toxicity of MPTP.
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Centre d'études et de Recherche sur les Xénobiotiques, UPRES EA 1223, 34, rue du Jardin des Plantes, BP 199, 86005 Cedex, Poitiers, France.
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D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology*; D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003342:Corpus Striatum / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism* / Q000493:pharmacokinetics; D015259:Dopamine Agents / Q000494:pharmacology; D050483:Dopamine Plasma Membrane Transport Proteins; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D008954:Models, Biological; D009419:Nerve Tissue Proteins; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D002352:Carrier Proteins; D015259:Dopamine Agents; D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine