The glutamate antagonist, MK-801, does not prevent dopaminergic cell death induced by the 1-methyl-4-phenylpyridinium ion (MPP+) in rat dissociated mesencephalic cultures.
The neuroprotective effects of MK-801, a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were assessed in a culture model which reproduces in vitro the selective degeneration of mesencephalic dopaminergic neurons seen in parkinsonian brains. Dissociated mesencephalic cells derived from rat embryonic brains were subjected for 24 h to intoxication by the 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPP+ at 3 and 10 microM produced selective and dose-dependent damages to dopaminergic neurons as quantified by the loss of the number of TH immunoreactive cells and the loss of [3H]DA uptake whereas other cell types remained unaffected. MK-801 at 3 and 10 microM failed to rescue degenerating dopaminergic neurons in presence of MPP+. At 50 microM, i.e. the highest concentration that is not toxic by itself in this culture system, MK-801 was also found ineffective. Furthermore, degree of dopaminergic cell damage was not reduced when repeated additions of the glutamate antagonist (10 microM/6 h for 24 h) were performed during exposure to MPP+ or when mesencephalic cultures were left after intoxication for up to 2 days in a culture medium still supplemented with MK-801 but free of toxin. In accordance with these results, MK-801 did not affect significantly the uptake of [3H]DA in control cultures, thereby suggesting that this compound cannot prevent intracellular accumulation of MPP+ within dopaminergic neurons. At higher concentrations of MPP+ (100 microM) tested, toxic effects were seen toward dopaminergic neurons and non-dopaminergic cells as quantified by Trypan blue dye accumulation and loss of [3H]GABA uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
INSERM U289, Hôpital de la Salpêtrière, Paris, France.
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Michel
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Agid
D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D016291:Dizocilpine Maleate / Q000494:pharmacology* / Q000633:toxicity; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates / Q000633:toxicity; D018698:Glutamic Acid; D007124:Immunoenzyme Techniques; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D012680:Sensitivity and Specificity; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016291:Dizocilpine Maleate; D014446:Tyrosine 3-Monooxygenase; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine