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- Errico, Francesco, et al.
(författare)
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Higher free d-aspartate and N-methyl-d-aspartate levels prevent striatal depotentiation and anticipate 1-DOPA-induced dyskinesia
- 2011
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Ingår i: Experimental Neurology. - : Elsevier BV. - 0014-4886 .- 1090-2430. ; 232:2, s. 240-250
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Tidskriftsartikel (refereegranskat)abstract
- In Parkinson's disease (PD) progressive alteration of striatal N-methyl-D-aspartate receptors (NMDARs) signaling has emerged as a considerable factor for the onset of the adverse motor effects of long-term levodopa (L-DOPA) treatment. In this regard, the NMDAR channel blocker amantadine is so far the only drug available for clinical use that attenuates L-DOPA-induced dyskinesia (LID). In this study, we examined the influence of a basal corticostriatal hyper-glutamatergic transmission in the appearance of dyskinesia, using a genetic mouse model lacking D-Aspartate Oxidase (DDO) enzyme (Ddo(-/-)mice). We found that, in Ddo(-/-)mice, non-physiological, high levels of the endogenous free D-amino acids D-aspartate (D-Asp) and NMDA, known to stimulate NMDAR transmission, resulted in the loss of corticostriatal synaptic depotentiation and precocious expression of LID. Interestingly, the block of depotentiation precedes any change in dopaminergic transmission associated to 6-OHDA lesion and L-DOPA treatment. Indeed, lesioned mutant mice display physiological L-DOPA-dependent enhancement of striatal D1 receptor/PKA/protein phosphatase-1 and ERK signaling. Moreover, in line with synaptic rearrangements of NMDAR subunits occurring in dyskinetic animal models, a short L-DOPA treatment produces a dramatic and selective reduction of the NR2B subunit in the striatal post-synaptic fraction of Ddo(-/-) lesioned mutants but not in controls. These data indicate that a preexisting hyper-glutamatergic tone at NMDARs in Ddo(-/-) mice produce abnormal striatal synaptic changes that, in turn, facilitate the onset of LID. (C) 2011 Elsevier Inc. All rights reserved.
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| 2. |
- Rylander, Daniella, et al.
(författare)
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Region-specific restoration of striatal synaptic plasticity by dopamine grafts in experimental parkinsonism.
- 2013
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:46, s. 4375-4384
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Tidskriftsartikel (refereegranskat)abstract
- Intrastriatal transplantation of dopaminergic neurons can restore striatal dopamine levels and improve parkinsonian deficits, but the mechanisms underlying these effects are poorly understood. Here, we show that transplants of dopamine neurons partially restore activity-dependent synaptic plasticity in the host striatal neurons. We evaluated synaptic plasticity in regions distal or proximal to the transplant (i.e., dorsolateral and ventrolateral striatum) and compared the effects of dopamine- and serotonin-enriched grafts using a rat model of Parkinson disease. Naïve rats showed comparable intrinsic membrane properties in the two subregions but distinct patterns of long-term synaptic plasticity. The ventrolateral striatum showed long-term potentiation using the same protocol that elicited long-term depression in the dorsolateral striatum. The long-term potentiation was linked to higher expression of postsynaptic AMPA and N2B NMDA subunits (GluN2B) and was dependent on the activation of GluN2A and GluN2B subunits and the D1 dopamine receptor. In both regions, the synaptic plasticity was abolished after a severe dopamine depletion and could not be restored by grafted serotonergic neurons. Solely, dopamine-enriched grafts could restore the long-term potentiation and partially restore motor deficits in the rats. The restoration could only be seen close to the graft, in the ventrolateral striatum where the graft-derived reinnervation was denser, compared with the distal dorsolateral region. These data provide proof of concept that dopamine-enriched transplants are able to functionally integrate into the host brain and restore deficits in striatal synaptic plasticity after experimental parkinsonism. The region-specific restoration might impose limitations in symptomatic improvement following neural transplantation.
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