| 1. |
- Lundblad, Martin, et al.
(author)
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Chronic intermittent L-DOPA treatment induces changes in dopamine release
- 2009
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 108:4, s. 998-1008
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Journal article (peer-reviewed)abstract
- 3,4-Dihydroxyphenyl-l-alanine (l-DOPA)-induced dyskinesia often develops as a side effect of chronic l-DOPA therapy. This study was undertaken to investigate dopamine (DA) release upon l-DOPA treatment. Chronoamperometric measurements were performed in unilaterally DA-depleted rats, chronically treated with l-DOPA, resulting in dyskinetic and non-dyskinetic animals. Normal and lesioned l-DOPA naïve animals were used as controls. Potassium-evoked DA releases were significantly reduced in intact sides of animals undertaken chronic l-DOPA treatment, independent on dyskinetic behavior. Acute l-DOPA further attenuated the amplitude of the DA release in the control sides. In DA-depleted striata, no difference was found in potassium-evoked DA releases, and acute l-DOPA did not affect the amplitude. While immunoreactivity to serotonin uptake transporter was higher in lesioned striata of animals displaying dyskinetic behavior, no correlation could be documented between serotonin transporter-positive nerve fiber density and the amplitude of released DA. In conclusions, the amplitude of potassium-evoked DA release is attenuated in intact striatum after chronic intermittent l-DOPA treatment. No change in amplitude was found in DA-denervated sides of either dyskinetic or non-dyskinetic animals, while release kinetics were changed. This indicates the importance of studying DA release dynamics for the understanding of both beneficial and adverse effects of l-DOPA replacement therapy.
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| 2. |
- Dekundy, A, et al.
(author)
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Effects of group I metabotropic glutamate receptors blockade in experimental models of Parkinson's disease
- 2006
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In: Brain Research Bulletin. - : Elsevier BV. - 0361-9230. ; 69:3, s. 318-326
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Journal article (peer-reviewed)abstract
- The present study was devoted to investigate the effects of the metabotropic glutamate receptor(mGluR)5 antagonist [(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) and the mGluR1 antagonist, (3-ethyl-2-methyl-quinolin-6-yl)-(4-methoxy-cyclohexyl)-methanone methanesulfonate (EMQMCM), in animal studies indicative of antiparkinsonian-like activity such as haloperidol-induced catalepsy, hypoactivity in open field following haloperidol, and rotation in rats with unilateral 6-hydroxydopamine(OHDA)-induced lesions of the midbrain dopaminergic system (alone and in combination with L-DOPA). Moreover, antidyskinetic activity of different mGluR ligands was evaluated in the rat model of L-DOPA-induced dyskinesia. Both MTEP (5 mg/kg) and EMQMCM (4 mg/kg) slightly inhibited haloperidol (0.5 mg/kg)-induced catalepsy. However, neither substance reversed the hypoactivity produced by haloperidol (0.2 mg/kg). Although MTEP and not produce significant turning, it inhibited contralateral rotations after L-DOPA (at 5 mg/kg) and alleviated L-DOPA-induced dyskinesia (at 2.5 and 5 mg/kg) in 6-OHDA-lesioned rats. In contrast, mGluR1 antagonists EMQMCM and RS-1-aminoindan-1,5-dicarboxylic acid (AIDA) failed to modify L-DOPA-induced dyskinesia. The results of the present study suggest that either subtype of group I of mGluRs may be involved in the pathologically altered circuitry in the basal ganglia. However, the equivocal results do not strongly support the hypothesis that mGluR1 and mGluR5 antagonists may be beneficial in the symptomatic treatment of Parkinson's disease. However, mGluR5 antagonists may prove useful for the symptomatic treatment Of L-DOPA-induced dyskinesia. (c) 2006 Elsevier Inc. All rights reserved.
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| 3. |
- Schuster, Stefan, et al.
(author)
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Antagonizing L-type Ca2+ Channel Reduces Development of Abnormal Involuntary Movement in the Rat Model of L-3,4-Dihydroxyphenylalanine-Induced Dyskinesia
- 2009
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In: Biological Psychiatry. - : Elsevier BV. - 0006-3223. ; 65:6, s. 518-526
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Journal article (peer-reviewed)abstract
- Background: Chronic L-3,4-dihydroxyphenylalanine (L-DOPA) treatment of Parkinson's disease (PD) leads to debilitating involuntary movements, termed L-DOPA-induced dyskinesia. Striatofugal medium spiny neurons (MSN) lose their dendritic spines and cortico-striatal glutamatergic synapses in PD and in experimental models of DA depletion. This loss of connectivity is triggered by a dysregulation of intraspine Cav1.3 L-type Ca2+ channels. Here we address the possible implication of DA denervation-induced spine pruning in the development of L-DOPA-induced dyskinesia. Methods: The L-type Ca2+ antagonist, isradipine was subcutaneously delivered to rats at the doses of .05, .1, or .2 mg/kg/day, for 4 weeks, starting the day after a unilateral nigrostriatal 6-hydroxydopamine (6-OHDA) lesion. Fourteen days later, L-DOPA treatment was initiated. Results: Isradipine-treated animals displayed a dose-dependent reduction in L-DOPA-induced rotational behavior and abnormal involuntary movements. Dendritic spine counting at electron microscopy level showed that isradipine (.2 mg/kg/day) prevented the 6-OHDA-induced spine loss and normalized preproenkephalin-A messenger RNA expression. Involuntary movements were not reduced when isradipine treatment was started concomitantly with L-DOPA. Conclusions: These results indicate that isradipine, at a therapeutically relevant dose, might represent a treatment option for preventing L-DOPA-induced dyskinesia in PD.
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| 4. |
- Valastro, Barbara, et al.
(author)
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Expression pattern of JunD after acute or chronic l-DOPA treatment: Comparison with DeltaFosB.
- 2007
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In: Neuroscience. - : Elsevier BV. - 1873-7544 .- 0306-4522. ; 144:Oct 19, s. 198-207
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Journal article (peer-reviewed)abstract
- In this study, we have used 6-hydroxydopamine-lesioned rats to examine changes in striatal junD and fosB/Delta fosB expression induced by acute and chronic treatment with (L)-DOPA (5 and 15 days). Changes at the protein levels were studied using Western immunoblotting while mRNA changes were compared using in situ hybridization histochemistry. We observed a significant increase in the level of Delta FosB proteins after chronic treatment with L-DOPA, an effect that was not observed for JunD proteins. In addition, the upregulation of Delta FosB was already present after an acute treatment but increased upon chronic treatment. By contrast, junD and Delta fosB mRNA were both upregulated significantly above control levels after an acute injection of L-DOPA. In conclusion, this study suggests a differential expression pattern of junD and Delta fosB in a rat model of L-DOPA-induced dyskinesia. The upregulation of Delta FosB protein, but not JunD, is likely to reflect an increased stability of the Delta FosB proteins without ongoing enhanced transcription of the encoding genes. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.
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