Related Experiment Videos
Uptake of 1-methyl-4-phenylpyridinium and dopamine in the mouse brain cell nuclei
1Clinical Research Institute of Montreal, Université de Montréal, Québec, Canada.
Abstract:
The neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite 1-methyl-4-phenylpyridinium (MPP+), parkinsonism in humans, monkeys, and mice but not in rats. When incubated with mouse brain homogenates, [3H]-MPP+ is recovered in relatively large concentrations in the brain cell nucleus. Although isolated cell nuclei from rat and mouse brain contain uptake systems for dopamine (DA), only brain cell nuclei from mice avidly take up [3H]MPP+. This nuclear uptake is ATP dependent and can be blocked by ouabain and N-ethylmaleimide. It is not, however, affected by neuronal and vesicular blockers such as benztropine, mazindol, and reserpine. Selective uptake of MPP+ into brain cell nuclei may provide a new avenue for future investigation into the complex modes of action of the neurotoxin MPTP.
Insights
The neurotoxin MPTP causes parkinsonism in mice but not rats. Researchers found that mouse brain cell nuclei, but not rat, selectively take up the toxin's metabolite MPP+, suggesting a potential mechanism for MPTP's selective toxicity.
Area of Science:
- Neuroscience
- Toxicology
Background:
- N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin that induces parkinsonism in various species.
- Its metabolite, 1-methyl-4-phenylpyridinium (MPP+), is implicated in this neurotoxic effect, but species-specific differences in susceptibility exist, notably between mice and rats.
Purpose of the Study:
- To investigate the differential uptake mechanisms of MPP+ in brain cell nuclei between mice and rats.
- To explore the potential role of nuclear uptake in the selective neurotoxicity of MPTP.
Main Methods:
- Incubation of mouse brain homogenates with [3H]-MPP+.
- Isolation of brain cell nuclei from rat and mouse.
- Assessment of [3H]-MPP+ uptake in isolated nuclei.
- Evaluation of the effects of ATP, ouabain, N-ethylmaleimide, benztropine, mazindol, and reserpine on MPP+ nuclear uptake.
Main Results:
- [3H]-MPP+ was recovered in high concentrations within mouse brain cell nuclei.
- Isolated mouse brain cell nuclei exhibited avid uptake of [3H]-MPP+, unlike rat brain cell nuclei.
- This selective nuclear uptake was ATP-dependent and inhibited by ouabain and N-ethylmaleimide.
- The uptake was unaffected by common neuronal and vesicular transport blockers.
Conclusions:
- Selective uptake of MPP+ into brain cell nuclei is a characteristic of species susceptible to MPTP neurotoxicity (e.g., mice).
- This nuclear accumulation mechanism may contribute to the differential toxicity of MPTP observed across species.
- Further research into this nuclear uptake pathway could elucidate MPTP's complex mechanisms of action.