Nigrostriatal Pathway (nigrostriatal + pathway)

Distribution by Scientific Domains

Selected Abstracts

Impaired water maze learning performance without altered dopaminergic function in mice heterozygous for the GDNF mutation

R. Gerlai
Abstract Exogenous glial cell line-derived neurotrophic factor (GDNF) exhibits potent survival-promoting effects on dopaminergic neurons of the nigrostriatal pathway that is implicated in Parkinson's disease and also protects neurons in forebrain ischemia of animal models. However, a role for endogenous GDNF in brain function has not been established. Although mice homozygous for a targeted deletion of the GDNF gene have been generated, these mice die within hours of birth because of deficits in kidney morphogenesis, and, thus, the effect of the absence of GDNF on brain function could not be studied. Herein, we sought to determine whether adult mice, heterozygous for a GDNF mutation on two different genetic backgrounds, demonstrate alterations in the nigrostriatal dopaminergic system or in cognitive function. While both neurochemical and behavioural measures suggested that reduction of GDNF gene expression in the mutant mice does not alter the nigrostriatal dopaminergic system, it led to a significant and selective impairment of performance in the spatial version of the Morris water maze. A standard panel of blood chemistry tests and basic pathological analyses did not reveal alterations in the mutants that could account for the observed performance deficit. These results suggest that endogenous GDNF may not be critical for the development and functioning of the nigrostriatal dopaminergic system but it plays an important role in cognitive abilities. [source]

Role of activity-dependent mechanisms in the control of dopaminergic neuron survival

Patrick P. Michel
Abstract Dopaminergic neurons that constitute the nigrostriatal pathway are characterized by singular electrical properties that allow them to discharge in vivo spontaneously in a spectrum of patterns ranging from pacemaker to random and bursting modes. These electrophysiological features allow dopaminergic neurons to optimize the release of dopamine in their terminal fields. However, there is emerging evidence indicating that electrical activity might also participate in the control of dopaminergic neuron survival, not only during development, but also in the adult brain, thus raising the possibility that alterations in ionic currents could contribute actively to the demise of these neurons in Parkinson disease. This review focuses on the mechanisms by which activity-dependent mechanisms might modulate dopaminergic cell survival. [source]

Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-,

Krishnan Sriram
Abstract Activated microglia are implicated in the pathogenesis of disease-, trauma- and toxicant-induced damage to the CNS, and strategies to modulate microglial activation are gaining impetus. A novel action of the tetracycline derivative minocycline is the ability to inhibit inflammation and free radical formation, factors that influence microglial activation. Minocycline is therefore being tested as a neuroprotective agent to alleviate CNS damage, although findings so far have yielded mixed results. Here, we showed that administration of a single low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (METH), a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in substantia nigra, increased the expression of mRNAs encoding microglia-associated factors F4/80, interleukin (IL)-1,, IL-6, monocyte chemoattractant protein-1 (MCP-1, CCL2) and tumor necrosis factor (TNF)-,. Minocycline treatment attenuated MPTP- or METH-mediated microglial activation, but failed to afford neuroprotection. Lack of neuroprotection was shown to be due to the inability of minocycline to abolish the induction of TNF-, and its receptors, thereby failing to modulate TNF signaling. Thus, TNF-, appeared to be an obligatory component of dopaminergic neurotoxicity. To address this possibility, we examined the effects of MPTP or METH in mice lacking genes encoding IL-6, CCL2 or TNF receptor (TNFR)1/2. Deficiency of either IL-6 or CCL2 did not alter MPTP neurotoxicity. However, deficiency of both TNFRs protected against the dopaminergic neurotoxicity of MPTP. Taken together, our findings suggest that attenuation of microglial activation is insufficient to modulate neurotoxicity as transient activation of microglia may suffice to initiate neurodegeneration. These findings support the hypothesis that TNF-, may play a role in the selective vulnerability of the nigrostriatal pathway associated with dopaminergic neurotoxicity and perhaps Parkinson's disease. [source]

Nigrostriatal denervation does not affect glutamate transporter mRNA expression but subsequent levodopa treatment selectively increases GLT1 mRNA and protein expression in the rat striatum

J.-C. Liévens
There is growing evidence that the loss of the nigrostriatal dopaminergic neurones induces an overactivity of the corticostriatal glutamatergic pathway which seems to be central to the physiopathology of parkinsonism. Moreover, glutamatergic mechanisms involving NMDA receptors have been shown to interfere with the therapeutical action of levodopa. Given the key role played by uptake processes in glutamate neurotransmission, this study examined the effects of nigrostriatal deafferentation and of levodopa treatment on the striatal expression of the glutamate transporters GLT1, GLAST and EAAC1 in the rat. No significant changes in striatal mRNA levels of these transporters were detected after either levodopa treatment (100 mg/kg; i.p., twice a day for 21 days) or unilateral lesion of the nigrostriatal pathway by intranigral 6-hydroxydopamine injection. In contrast, animals with the lesion subsequently treated with levodopa showed a selective increase (36%) in GLT1 mRNA levels in the denervated striatum versus controls. These animals also showed increased GLT1 protein expression, as assessed by immunostaining and western blotting. These data provide the first evidence that levodopa therapy may interfere with striatal glutamate transmission through change in expression of the primarily glial glutamate transporter GLT1. We further suggest that levodopa-induced GLT1 overexpression may represent a compensatory mechanism preventing neurotoxic accumulation of endogenous glutamate. [source]

Effect of estradiol on striatal dopamine activity of female hemiparkinsonian monkeys

Marc Morissette
Abstract A higher prevalence and incidence of Parkinson's disease is observed in men, and beneficial motor effects of estrogens are observed in parkinsonian women. In rodents, an effect of estradiol on dopamine systems is documented, whereas much less is known in monkeys. Enkephalin was shown to exert a compensatory modulatory effect on the denervated dopamine nigrostriatal pathway in monkeys and in humans. Moreover in rodents, striatal preproenkephalin mRNA is increased by estrogen treatment. Hence, we investigated the responsiveness of striatal dopamine to estradiol in long-term ovariectomized monkeys bearing a unilateral lesion with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to mimic parkinsonian postmenopausal women. Seven ovariectomized female monkeys received a unilateral MPTP lesion; 4 years after ovariectomy, three received 1-month treatment with 17,-estradiol and the others received vehicle. The lesioned striata showed extensive denervation in all monkeys as measured with dopamine and metabolite concentrations assayed by high-performance liquid chromatography and by autoradiography of the dopamine transporter. The lesioned and intact striata of estradiol-treated monkeys had increased 3-methoxytyramine, and lesioned putamen increased dopamine concentrations compared with vehicle-treated monkeys. Estradiol treatment increased the dopamine transporter in subregions of the intact caudate and putamen compared with the intact striata of vehicle-treated monkeys, but not in the lesioned striata. Preproenkephalin mRNA levels measured by in situ hybridization were increased in the lesioned striata of vehicle treated monkeys and were not further enhanced in estradiol-treated monkeys. These results show that long after ovariectomy, modeling postmenopausal hormonal conditions, brain dopamine metabolism, and transporter are still responsive to estradiol. © 2008 Wiley-Liss, Inc. [source]

When does Parkinson's disease begin?,

Carles Gaig MD
Abstract Pathological and neuroimaging studies have shown that in Parkinson's disease (PD) there is a "subclinical" or "premotor" period during which dopaminergic neurons in the substantia nigra (SN) degenerate but typical motor symptoms have not yet developed. Post-mortem studies based on nigral cell counts and evaluating dopamine levels in the striata, and imaging studies assessing the nigrostriatal pathway in vivo, have estimated that this time period could last 3 to 6 years. In addition, emerging evidence indicates that the neuropathological process of PD does not start in the SN but more likely elsewhere in the nervous system: in the lower brainstem and the olfactory bulb, or even more distant from the SN, such as in the peripheral autonomic nervous system. Patients with PD frequently can present non-motor symptoms, such as hyposmia or constipation, years before the development of classical motor signs. The physiopathology of these "premotor" symptoms, though still unclear, is currently thought to be related to early involvement by the pathological process underlying PD of non-dopaminergic lower brainstem structures or autonomic plexuses. However, the answer to the question "when does PD start" remains uncertain. Here, we review clinical, pathological, and neuroimaging data related to the onset of the pathological process of PD, and propose that its onset is non-motor and that non-motor symptoms could begin in many instances 10 and 20 years before onset of motor symptoms. The variable course of the disorder once the motor symptoms develop, suggests that the start and progression of premotor PD is also highly variable andgiven the heterogeneous nature of PD, may differ depending on the cause/s of the syndrome. When and where the neuropathological process develops in PD remains uncertain. © 2009 Movement Disorder Society [source]

Posttraumatic tremor without parkinsonism in a patient with complete contralateral loss of the nigrostriatal pathway,

Jan Zijlmans MD
We present a patient with posttraumatic tremor who did not show any [123I]FP-CIT uptake in the contralateral putamen and caudate. The absence of hypokinesia and rigidity is surprising in the presence of a striatal dopaminergic denervation that is even more severe than in Parkinson's disease. An explanation, therefore, could be that the lesion in the subthalamic nucleus in our patient prevented the onset of a Parkinson syndrome. © 2002 Movement Disorder Society [source]

Clinical, neuroimaging and neurophysiological features in addicts with manganese-ephedrone exposure

K. Sikk
Sikk K, Taba P, Haldre S, Bergquist J, Nyholm D, Askmark H, Danfors T, Sörensen J, Thurfjell L, Raininko R, Eriksson R, Flink R, Färnstrand C, Aquilonius S-M. Clinical, neuroimaging and neurophysiological features in addicts with manganese-ephedrone exposure. Acta Neurol Scand: 2010: 121: 237,243. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objective,,, To identify biomarkers supporting the clinical diagnosis of manganism in patients several years after exposure to manganese (Mn). Methods,,, Neurophysiological examinations, magnetic resonance imaging (MRI), single-photon emission computed tomography and fluorodeoxyglycose (FDG) positron emission tomography were performed in four former ephedrone addicts with extrapyramidal symptoms. Results,,, Peripheral nervous system was not affected. No patients had reduced uptake of 123I Ioflupane in the striatum. MRI signal intensities were slightly changed in the basal ganglia. All patients showed a widespread, but not uniform, pathological pattern of FDG uptake with changes mainly located to the central part of the brain including the basal ganglia and the surrounding white matter. Conclusions,,, Presynaptic neurons in the nigrostriatal pathway are intact in Mn-induced parkinsonism after prolonged abstinence from ephedrone. The diagnosis is principally based on clinical signs and the history of drug abuse. [source]

The clinical and neuroimaging studies in Holmes tremor

A. Gajos
Gajos A, Bogucki A, Schinwelski M, So,tan W, Rudzi,ska M, Budrewicz S, Koszewicz M, Majos A, Górska-Chrz,stek M, Bie,kiewicz M, Ku,mierek J, S,awek J. The clinical and neuroimaging studies in Holmes tremor. Acta Neurol Scand: 2010: 122: 360,366. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Aim,,, Holmes tremor (HT) is a combination of rest, postural and action tremor. A parallel dysfunction of cerebello-thalamic and nigrostriatal pathways seems necessary to produce this kind of tremor. We present the clinical and neuroimaging study verifying that hypothesis. Material and methods,,, A total of 10 patients: five male, five female, fulfilling consensus criteria were included. Demographic, clinical and neuroimaging data (MRI = 9; CT = 1, SPECT with the use of 123-I-FP CIT: DaTSCAN in six patients to assess the presynaptic dopaminergic nigrostriatal system involvement, indices of asymmetry for ligand uptake for each striatum were calculated) were analyzed. Results,,, Hemorrhage was the most frequent etiology and thalamus , the most commonly involved structure. Contrary to the previous reports, the visual assessment did not reveal remarkable interhemispheric differences of DaTSCAN uptake. Quantitative measurements showed only minimal differences. Conclusions,,, It is open to debate whether nigrostriatal pathway damage is crucial for the phenomenology of HT. Alternative hypothesis is presented that HT represents the heterogeneous spectrum of tremors with similar phenomenology, but different pathophysiology. [source]