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|Section2= |Section3= }} MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a neurotoxin precursor to MPP+, which causes permanent symptoms of Parkinson's disease by destroying dopaminergic neurons in the substantia nigra of the brain. It has been used to study disease models in various animal studies. While MPTP itself has no psychoactive effects, the compound may be accidentally produced during the manufacture of MPPP, a synthetic opioid drug with effects similar to those of morphine and pethidine (meperidine). The Parkinson-inducing effects of MPTP were first discovered following accidental ingestion as a result of contaminated MPPP. ==Toxicity== Injection of MPTP causes rapid onset of Parkinsonism, hence users of MPPP contaminated with MPTP will develop these symptoms. MPTP itself is not toxic, and as a lipophilic compound can cross the blood–brain barrier. Once inside the brain, MPTP is metabolized into the toxic cation 1-methyl-4-phenylpyridinium (MPP+) by the enzyme MAO-B of glial cells. MPP+ kills primarily dopamine-producing neurons in a part of the brain called the pars compacta of the substantia nigra. MPP+ interferes with complex I of the electron transport chain, a component of mitochondrial metabolism, which leads to cell death and causes the buildup of free radicals, toxic molecules that contribute further to cell destruction. Because MPTP itself is not directly harmful, toxic effects of acute MPTP poisoning can be mitigated by the administration of monoamine oxidase inhibitors (MAOIs) such as selegiline. MAOIs prevent the metabolism of MPTP to MPP+ by inhibiting the action of MAO-B, minimizing toxicity and preventing neural death. MPP+ has quite selective abilities to cause neuronal death in dopaminergic cells, it is presumed through a high-affinity uptake process in nerve terminals normally used to reuptake dopamine after it has been released into the synaptic cleft. The dopamine transporter moves MPP+ inside the cell. The resulting gross depletion of dopaminergic neurons has severe implications on cortical control of complex movements. The direction of complex movement is based from the substantia nigra to the putamen and caudate nucleus, which then relay signals to the rest of the brain. This pathway is controlled via dopamine-using neurons, which MPTP selectively destroys, resulting over time in parkinsonism. MPTP causes Parkinsonism in primates including humans. Rodents are much less susceptible. Rats are almost immune to the adverse effects of MPTP. Mice were thought to only suffer from cell death in the substantia nigra (to differing degree according to the strain of mice used) but do not show Parkinsonian symptoms, however most of the recent studies indicate that MPTP can result in Parkinsonism-like syndromes in mice (especially chronic syndromes).〔(【引用サイトリンク】 Parkinson’s Disease Models )〕 It is believed that the lower levels of MAO-B in the rodent brain's capillaries may be responsible for this.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「MPTP」の詳細全文を読む スポンサード リンク
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