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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Previous studies from this laboratory demonstrated that (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801), an N-methyl-D-aspartate (NMDA) receptor antagonist, did not prevent neurotoxicity to dopaminergic neurons in mice produced by systemic treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). However, Turski et al. [Nature349, 414–418 (1991)] reported that extended treatment of rats with NMDA receptor antagonists (six injections at 4-h intervals) did prevent the loss of nigral dopaminergic neurons resulting from an intranigral infusion of 1-methyl-4-phenylpyridinium (MPP+), the neurotoxic metabolite of MPTP. The present studies examined if a similar extended treatment with MK-801 would protect mice from the neurotoxicity of systemically administered MPTP. Six intraperitoneal injections of MK-801 given at 4-h intervals did not protect mice against the MPTP-induced neostriatal dopamine loss measured 1 week after treatment. In other experiments, designed to replicate and expand on the results of Turski et al. (1991), the extended treatment of rats with MK-801 did not prevent MPP+-induced cell loss in the infused substantia nigra pars compacta or the dopamine depletion in the ipsilateral neostriatum at 7-11 days after MPP+ infusion. These results do not support the hypothesis that NMDA receptors are involved with MPTP/MPP+-induced neurodegeneration.
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: 1-Methyl-4-phenyl- 1,2,5,6 -tetrahydropyridine (MPTP) is a chemical that, after injection into experimental animals, including mice and monkeys, causes a degeneration of the nigrostriatal pathway. We carried out experiments designed to study the in vitro oxidation of MPTP by mouse brain mitochondrial preparations. MPTP was actively oxidized by the mitochondrial preparations, with Km and Vmax values very similar to those of benzyl amine, a typical substrate for MAO-B. MPTP was oxidized considerably better than many of its analogs, even those with relatively minor structural changes. Several monoamine oxidase inhibitors (MAOI) were potent inhibitors of MPTP oxidation, and there was a highly significant correlation between the capacity of the MAOI tested to inhibit MPTP oxidation and benzylamine oxidation. There was no correlation between the capacity of the MAOI to inhibit MPTP oxidation and their capacity to inhibit the oxidation of tryptamine, a substrate for MAO-A. In other experiments, MPTP was an excellent substrate for pure MAO-B, prepared from bovine liver. All of these data. combined with the fact that MAO-B inhibitors can protect against MPTP-induced dopami nergic neurotoxicity in vivo. point to an important role for MAO-B in MPTP metabolism in vivo.
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The neurotoxic actions of methamphetamine (METH) may be mediated in part by reactive oxygen species (ROS). Methamphetamine administration leads to increases in ROS formation and lipid peroxidation in rodent brain; however, the extent to which proteins may be modified or whether affected brain regions exhibit similar elevations of lipid and protein oxidative markers have not been investigated. In this study we measured concentrations of TBARs, protein carbonyls and monoamines in various mouse brain regions at 4 h and 24 h after the last of four injections of METH (10 mg/kg/injection q 2 h). Substantial increases in TBARs and protein carbonyls were observed in the striatum and hippocampus but not the frontal cortex nor the cerebellum of METH-treated mice. Furthermore, lipid and protein oxidative markers were highly correlated within each brain region. In the hippocampus and striatum elevations in oxidative markers were significantly greater at 24 h than at 4 h. Monoamine levels were maximally reduced within 4 h (striatal dopamine [DA] by 95% and serotonin [5-HT] in striatum, cortex and hippocampus by 60–90%). These decrements persisted for 7 days after METH, indicating effects reflective of nerve terminal damage. Interestingly, NE was only transiently depleted in the brain regions investigated (hippocampus and cortex), suggesting a pharmacological and non-toxic action of METH on the noradrenergic nerve terminals. This study provides the first evidence for concurrent formation of lipid and protein markers of oxidative stress in several brain regions of mice that are severely affected by large neurotoxic doses of METH. Moreover, the differential time course for monoamine depletion and the elevations in oxidative markers indicate that the source of oxidative stress is not derived directly from DA or 5HT oxidation.
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1-Methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) is known to cause a destruction of the dopaminergic nigrostriatal pathway in certain animal species including mice. MPTP and some structurally related analogs were tested in vitro for their capacity to inhibit the uptake of [3H]3,4-dihydroxyphenylethylamine-([3H]DA), [3H]5-hydroxytryptamine ([3H]5-HT), and [3H]γ-aminobutyric acid ([3H]GABA) in mouse neostriatal synaptosomal preparations. MPTP was a very potent inhibitor of [3H]5-HT uptake (IC50 value 0.14 μM), a moderate inhibitor of [3H]DA uptake (IC50 value 2.6 μM), and a very weak inhibitor of [3H]GABA uptake (no significant inhibition observed at 10 μM MPTP). In other experiments, MPTP caused some release of previously accumulated [3H]DA and [3H]5-HT, but in each case MPTP was considerably better as an uptake inhibitor than as a releasing agent. The 4-electron oxidation product of MPTP, i.e., 1-methyl-4-phenyl-pyridinium iodide (MPP+), was a very potent inhibitor of [3H]DA uptake (IC50 value 0.45 μM) and of [3H]5-HT uptake (IC50 value 0.78 μM) but MPP+ was a very weak inhibitor of [3H]GABA uptake. These data may have relevance to the neurotoxic actions of MPTP.
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Ascorbic acid, sodium ascorbate, and isoascorbic acid (the stereo-isomer of ascorbic acid) inhibited the stereospecific binding of [3H]spiroperidol to neostriatal membrane preparations. Greater inhibitory effects were obtained at intermediate concentrations of the three ascorbic acid analogs (i.e., 0.06 and 0.6 mM) than at higher (6 mM) or lower (0.006 mM) concentrations. In parallel experiments, the three ascorbic acid analogs induced lipid peroxidation, which was also greater at the two intermediate than at higher or lower concentrations. Several known inhibitors of lipid peroxidation, including propyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, α-naphthol, and cobalt chloride, as well as the iron chelating agents EDTA and DETAPAC (diethylenetriaminepentaacetic acid) were able to counteract the effects of the ascorbic acid analogs on both lipid peroxidation and on [3H]spiroperidol binding. These data strongly suggest that an iron-catalyzed lipid peroxidation is responsible for the observed inhibitory effects on binding. In other experiments, neostriatal membrane preparations that were preincubated with ascorbic acid (0.6 mM) and subsequently washed still had greatly diminished capacity to bind [3H]spiroperidol, indicating that ascorbic acid need not be physically present during the binding assay in order to affect binding. This experimental procedure also appears to be a way in which [3H]spiroperidol binding sites can be inactivated and washed free of the inactivating agent.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 648 (1992), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 498 (1987), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Male, Swiss-Webster mice weighing 25-35 g were injected intraperitoneally with pargyline, deprenil, clorgyline, tranylcypromine or nialamide and subsequently received MPTP. As Table 1 shows, 3 days after the last of five injections of MPTP, 30 mg per kg, the mean neostriatal content of dopamine ...
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