Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pedunculopontine tegmental nucleus (PPTg) has been shown to have cholinergic connections with the thalamus and basal ganglia. The ability of various doses of the excitotoxins (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) (AMPA), folate, ibotenate, kainate, N-methyl-D-aspartate (NMDA), quinolinate and quisqualate to make lesions in the PPTg was examined, with particular reference to their ability to destroy cholinergic neurons identified using choline acetyltransferase (ChAT) immunohistochemistry. All of the toxins induced convulsive activity on recovery from surgical anesthesia and all except folate made lesions in the PPTg and surrounding structures. The size of the lesions was computed following examination of Cresyl violet stained sections. The largest lesions were made by kainate = AMPA greater than NMDA = ibotenate greater than quisqualate = quinolinate. All of the toxins destroyed cholinergic neurons, higher doses producing greater loss than lower. The ratio of cholinergic cell loss to general neuronal loss (assessed by Cresyl violet staining) was also computed, revealing marked differences between the toxins. Statistical analysis showed that there were significant differences between excitotoxins in terms of this ratio, but these were accounted for by the low dose of quinolinate (24 nmol) producing a significantly greater ratio of damage (12.18:1) than every other toxin. (Next highest ratio: quisqualate 60 nmol, 6.22:1.) Between the other toxins (kainate, AMPA, ibotenate, quisqualate, NMDA and the high dose of quinolinate) there were no statistically significant differences. Intense calcium deposits (stained by Alizarin red) were found frequently and often defined the borders of the lesion. Tyrosine hydroxylase immunohistochemistry revealed axons running below and into the area of lesioned tissue suggesting strongly that fibers were undamaged by the lesions. We conclude that in the PPTg, different excitotoxins make discriminably different lesions, both quantitatively and qualitatively. Unlike excitotoxic lesions in the basal forebrain quinolinate, not quisqualate, made the most selective lesions of cholinergic neurons and, unlike excitotoxic lesions in the septal nuclei, non-myelinated fibers were spared by ibotenate. The implications of these data for research into brainstem mechanisms of Parkinson's disease are discussed.
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PMID:Excitotoxic lesions of the pedunculopontine tegmental nucleus of the rat. I. Comparison of the effects of various excitotoxins, with particular reference to the loss of immunohistochemically identified cholinergic neurons. 138 12

Advance in understanding of the anatomy, physiology and pharmacology of basal ganglia organisation over the past decade revealed a functional relation between excitatory glutamatergic and the degenerated dopaminergic nigrostriatal transmitter systems which could serve as targets for pharmacological interventions in Parkinson's disease. The selective AMPA-antagonist NBQX is not effective in animal models of Parkinson's disease when given alone but ameliorates parkinsonian symptomatology and enhances the locomotor response of a threshold dose of L-DOPA. These synergistic effects are seen in the MPTP-treated (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) common marmoset and the rat with unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra. Here we report that, in the latter model, such synergism of NBQX is also seen with the direct dopamine agonists lisuride and apomorphine, indicating the potential usefulness of AMPA antagonists for the symptomatic treatment of Parkinson's disease.
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PMID:Synergism of NBQX with dopamine agonists in the 6-OHDA rat model of Parkinson's disease. 149 Dec 48

Degeneration of dopaminergic nigrostriatal neurons in Parkinson's disease results in an overactivity of excitatory glutamatergic projections from the subthalamic nucleus to the output nuclei of the basal ganglia resulting in rigidity and akinesia. In theory pharmacological blockade of these overactive systems should improve parkinsonian symptomatology. The selective AMPA-antagonist NBQX and the competitive NMDA-antagonist CPP are not effective in animal models of Parkinson's disease when given alone but ameliorate parkinsonian symptomatology and stimulate locomotor activity when co-administered with a threshold dose of L-Dopa. These synergistic effects are seen in the MPTP-treated (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) common marmoset and the rat with unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra. Therefore competitive NMDA and non-NMDA antagonists may offer a new therapeutic strategy for the treatment of Parkinson's disease.
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PMID:Synergism of the AMPA-antagonist NBQX and the NMDA-antagonist CPP with L-dopa in models of Parkinson's disease. 183 81

This review describes recent advances in our understanding of the pharmacology of excitatory amino acid receptors, and the application of this knowledge to the unravelling of the aetiology of neurodegenerative diseases, and to their therapy. Ionotropic excitatory amino acid receptors can be divided into two large families, the NMDA receptor family, and the AMPA/kainate receptor family. Receptor cloning studies have shown there to be a large number of potential subtypes of receptors in both these families. Antagonists have been developed for the NMDA receptor which can interact with at least four independent drug recognition sites on the receptor. For the AMPA/kainate receptor, two classes of antagonist have so far been identified. Reasonably potent, selective and brain-penetrating antagonists now exist for virtually all these sites, and compounds inhibiting the release of glutamic acid presynaptically have also been identified, such as riluzole. The ability of glutamic acid to kill neurons (excitotoxicity) seems to be mediated, in most cases, by an interaction with NMDA receptors, leading to an uncontrollable rise in intracellular calcium concentrations and thence cell lysis and death. The setting-up of glutamatergic loops seems to be a key process in the maintenance, spread and amplification of neurodegenerative foci. The existence of such processes has been amply demonstrated in animal models of stroke, in which both NMDA and AMPA/kainate receptor antagonists have neuroprotective effects. Clinical trials are underway with NMDA receptor antagonists in stroke. Excitotoxic mechanisms probably also contribute to pathology in head trauma and viral encephalopathy. Ingestion of excitatory amino acids may play a role in neurological conditions of dietary aetiology, such as neurolathyrism and domoic acid intoxication. For chronic neurodegenerative diseases, the role of excitatory amino acids is much less clear, although there is some evidence for the existence of excitotoxic mechanisms in amyotrophic lateral sclerosis. Evidence from animal models suggests that drugs that block glutamatergic neurotransmission might be beneficial in Parkinson's disease, Huntington's chorea and amyotrophic lateral sclerosis, but the relevance of these animal models to the human pathology is not clear. However, preliminary clinical results suggest riluzole to be efficacious in prolonging survival in amyotrophic lateral sclerosis, and certain weak NMDA receptor antagonists are currently used in the treatment of Parkinson's disease. The next few years could witness a breakthrough in the treatment of neurological conditions as drugs that interfere with glutamatergic transmission become available for clinical use.
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PMID:Excitatory amino acid receptors and neurodegeneration. 748 87

NMDA and non-NMDA (AMPA/kainate) antagonists have potential in the treatment of a diverse group of neurological disorders associated with excessive activation of excitatory amino acid receptors. Here Michael Rogawski reviews recent progress in the development of therapeutically useful NMDA receptor channel blockers and a new class of selective AMPA/kainate receptor antagonists, the 2,3-benzodiazepines. Research on these novel noncompetitive excitatory amino acid antagonists has opened promising new avenues for the development of drugs to treat epilepsy, ischaemia, neurodegeneration and Parkinson's disease.
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PMID:Therapeutic potential of excitatory amino acid antagonists: channel blockers and 2,3-benzodiazepines. 750 60

The aim of this article was to review the recent literature on the role of excitatory amino acids in Parkinson's disease and in animal equivalents of parkinsonian symptoms. Effects of NMDA and AMPA antagonists on the reserpine-induced akinesia, catalepsy and rigidity, on the neuroleptic-induced catalepsy, on the turning behaviour of 6-OHDA-lesioned rats, as well as on the parkinsonian symptoms evoked by MPTP in monkeys were analysed. Moreover, the role of NMDA antagonists in Parkinson's disease was discussed. Data concerning the protective influence of these drugs on degenerative properties of methamphetamine, MPTP and 6-OHDOPA were also presented. On the basis of the above findings, the following conclusions may be drawn: (1) disturbances in the glutamatergic transmission in various brain structures seem to play a significant role in the development of symptoms of Parkinson's disease; (2) the NMDA-receptor blocking component may make a substantial contribution to the therapeutic effect of antiparkinsonian drugs; a similar contribution of AMPA-receptor blocking component has not been sufficiently documented, so far; (3) compounds blocking NMDA receptors may possibly prevent the development of Parkinson's disease; this presumption needs, however further studies; (4) side effects of NMDA receptor antagonists may be a limiting factor in the use of these compounds in humans.
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PMID:The role of excitatory amino acids in experimental models of Parkinson's disease. 753 62

It has previously been shown that glutamatergic overactivity of the subthalamic nucleus (STN) is involved in hypokinetic movement disorders such as Parkinson's disease. Conversely, it has been hypothesized that hyperkinetic behavioral syndromes may be associated with reduced glutamatergic transmission of the STN to its target areas, the substantial nigra pars reticulata (SNR) and the globus pallidus pars interna (GPI). In the present experiment, apomorphine injected systemically into unilaterally dopamine-denervated rats induced the hyperkinetic syndrome of contralateral rotation. The involvement of glutamatergic input to the SNR in this hyperkinesia was investigated by pharmacological manipulation with an agonist or an antagonist at the AMPA subtype of glutamate receptors. Either the agonist AMPA or the antagonist CNQX was infused directly into the SNR at a dose of 1.0 nmol. Intra-SNR AMPA attenuated the contralateral rotation induced by apomorphine without eliciting any effects on rotation by itself. Infusions of the antagonist CNQX did not affect either apomorphine-induced or spontaneous rotation. These results support the notion that underactivity of the SNR and its glutamatergic afferent projection from the STN may underlie hyperkinetic movement disorders and that local stimulation of the AMPA subtype of glutamate receptors can ameliorate such syndromes.
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PMID:Intra-nigra infusion of AMPA attenuates dopamine-dependent rotation in the rat. 769 18

The recent availability of selective ligands for NMDA and AMPA receptors has enabled neuroscientists to test the hypothesis that Parkinson's disease is a glutamate hyperactivity disorder and hence treatable with glutamate antagonists. This review takes a critical look at the motor characteristics of this new class of drugs in rodent and primate models of parkinsonism and assesses the clinical potential and pitfalls of this radical new approach. Monotherapy of Parkinson's disease with glutamate antagonists appears impractical at the present time, due to their low efficacy and unacceptable side effects, but polypharmacy with L-DOPA and a glutamate antagonist as adjuvant is a more realistic prospect. This review will focus on the ways in which glutamate receptor blockade facilitates motor recovery with L-DOPA and will examine whether the basis for this beneficial effect can be traced to a specific interaction with dopamine at D1 or D2 receptors, and therefore to discrete motor pathways within the basal ganglia.
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PMID:Glutamate/dopamine D1/D2 balance in the basal ganglia and its relevance to Parkinson's disease. 779 21

Quantitative receptor autoradiography using [3H]MK-801, [3H]glycine, [3H]CNQX and [3H]kainate was employed to determine the distribution and density of excitatory amino acid (EAA) binding sites in the midbrain and basal ganglia of the normal human nervous system. Detailed knowledge of the anatomy and subtype specificity of glutamate receptors is important both in understanding the normal physiology of basal ganglia neurotransmission and the pathophysiological changes occurring in diseases affecting the basal ganglia such as Parkinson's disease (PD). In PD, glutamate receptor activation may contribute to cell death of dopaminergic neurones in the substantia nigra. In addition, perturbation of glutamate neurotransmission resulting from dopamine depletion in the basal ganglia is likely to contribute to the clinical manifestations of motor dysfunction. The distribution and density of ligand binding representing N-methyl-D-aspartate (NMDA), AMPA (2-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) and kainate receptors has a heterogeneous distribution in the human midbrain and basal ganglia. In the substantia nigra relatively high densities of [3H]MK-801 and strychnine-insensitive [3H]glycine binding sites representing NMDA receptors were present, whereas only moderate densities of [3H]CNQX and [3H]kainate binding sites were present, compared to other regions. In both the medial globus pallidus and subthalamic nucleus, binding sites representing NMDA, AMPA and kainate receptors were all present at low density. These findings suggest that the clinical usefulness of modifying glutamatergic neurotransmission in these basal ganglia nuclei may be limited by the relatively low density of EAA binding sites present.
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PMID:The distribution of excitatory amino acid receptors in the normal human midbrain and basal ganglia with implications for Parkinson's disease: a quantitative autoradiographic study using [3H]MK-801, [3H]glycine, [3H]CNQX and [3H]kainate. 783 43

An assortment of glutamate antagonists with differing selectivities for NMDA and AMPA-type glutamate receptors, were tested for their effects in the mouse pilocarpine model of complex partial seizures. MK 801 (0.1-0.8 mg/kg) and high doses of HA 966 (50 mg/kg) were proconvulsant, whilst CGP 40116 (1-8 mg/kg) and low doses of HA 966 (0.4-10 mg/kg) inhibited pilocarpine-induced convulsions. CPP (5-20 mg/kg) and NBQX (1-50 mg/kg) were without effect. The dopamine D1 agonist SKF 38393 (10 mg/kg) facilitated the convulsant effects of low-dose pilocarpine (100 mg/kg). MK 801 (0.1-0.2 mg/kg) and HA 966 (50 mg/kg) interacted synergistically with SKF 38393 to promote the proconvulsant effects of D1 stimulation, whilst CPP (10-20 mg/kg) and HA 966 (10 mg/kg) had the opposite effect. CGP 40116 and NBQX were without effect. These results show that the convulsant qualities of MK 801 and SKF 38393, that have been detected in animal models of Parkinson's disease, can be reproduced in the pilocarpine model of epilepsy. Whilst the glutamate antagonists all interact synergistically with SKF 38393 to improve its antiparkinson activity, only MK 801 and high doses of HA 966 similarly potentiate the convulsions associated with D1 stimulation. An appropriate mixture of a glutamate antagonist and a D1 agonist could theoretically be used beneficially in the treatment of Parkinson's disease, without causing epilepsy as a side effect.
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PMID:Glutamate-dopamine interactions in the production of pilocarpine motor seizures in the mouse. 790 44


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