AMPA-induced extracellular Zn 2+ influx into nigral dopaminergic neurons causes movement disorder in rats

On the basis of the findings that the rapid influx of extracellular Zn into nigral dopaminergic neurons causes dopaminergic neurodegeneration, here we report that AMPA causes movement disorder in rats. AMPA markedly increased turning behavior in response to apomorphine 1 and 2 weeks after AMPA injection into the substantia nigra pars compacta (SNpc), while AMPA-induced movement disorder was suppressed by co-injection of intracellular Zn chelators, i.e., ZnAF-2DA and TPEN, suggesting that AMPA-induced movement disorder is due to intracellular Zn dysregulation. Furthermore, AMPA markedly induced loss of nigrostriatal dopaminergic neurons 2 weeks after AMPA injection into the SNpc, while AMPA-induced neurodegeneration was also suppressed in the SNpc and the striatum by co-injection of ZnAF-2DA and TPEN. AMPA rapidly increased nigral intracellular Zn after AMPA injection into the SNpc and this increase was blocked by co-injection of TPEN. These results indicate that AMPA receptor activation rapidly increases influx of extracellular Zn into nigral dopaminergic neurons and causes nigrostriatal dopaminergic neurodegeneration, resulting in movement disorder in rats. The evidence that AMPA-induced intracellular Zn dysregulation causes movement disorder via nigrostriatal dopaminergic neurodegeneration suggests that AMPA receptors, probably Ca - and Zn -permeable GluR2-lacking AMPA receptors are potential targets for overcoming Parkinson's syndrome.