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  • 1
    ISSN: 1432-0568
    Keywords: Key words Non-autoradiographic in situ hybridization ; Riboprobes ; GAD 65 ; Glia ; Glutamate transporters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The distributions in rat cerebral cortex and thalamus of the mRNAs encoding the glutamate transporters GLT1 and rEAAC1 (a rat homologue of rabbit EAAC1) were investigated by nonautoradiographic in situ hybridization using digoxigenin-labelled riboprobes. The probe recognizing rEAAC1 mRNA labelled exclusively neurons while GLT1 mRNA was found in glia as well as in select neuronal populations. The neurons containing the GLT1 transcript exhibited a distribution that was different from, and at some sites complementary to, the distribution of neurons containing rEAAC1 mRNA. In the subiculum, neurons positive for GLT1 and rEAAC1 were found in the deep and superficial part of the cell layer, respectively, while in the parietal neocortex GLT1 predominated in layer VI and rEAAC1 in layer V. Very few neuronal populations, most notably cells in hippocampal subfields CA3 and CA4, and in layer II in the entorhinal cortex, appeared to be equipped with both transcripts. In the thalamus the GLT1 labelling predominated in the midline and intralaminar nuclei while rEAAC1 labelling was found throughout this structure. It was concluded that the cerebral cortex and thalamus show cellular, laminar, as well as regional heterogeneities in the expression of the two glutamate transporters.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Hippocampus ; Ischemia ; Glial glutamate transporter ; In situ hybridization ; Immunoblotting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Perturbations of the synaptic handling of glutamate have been implicated in the pathogenesis of brain damage after transient ischemia. Notably, the ischemic episode is associated with an increased extracellular level of glutamate and an impaired metabolism of this amino acid in glial cells. Glutamate uptake is reduced during ischemia due to breakdown of the electrochemical ion gradients across neuronal and glial membranes. We have investigated, in the rat hippocampus, whether an ischemic event additionally causes a reduced expression of the glial glutamate transporter GLT1 (Pines et al. 1992) in the postischemic phase. Quantitative immunoblotting, using antibodies recognizing GLT1, revealed a 20% decrease in the hippocampal contents of the transporter protein, 6 h after an ischemic period lasting 20 min induced by four vessel occlusion. In situ hybridization histochemistry with 35S labelled oligonucleotide probes or digoxigenin labelled riboprobes directed to GLT1 mRNA showed a decreased signal in the hippocampus, particularly in CA1. This reduction was more pronounced at 3 h than at 24 h after the ischemic event. We conclude that the levels of GLT1 mRNA and protein show a modest decrease in the postischemic phase. This could contribute to the delayed neuronal death typically seen in the hippocampal formation after transient ischemia.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 7 (1995), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Membrane-localized transporter proteins, expressed in both neurons and glial cells, are responsible for removal of extracellular glutamate in the mammalian CNS. The amounts and activities of these transporters may be under regulatory control. We demonstrate here that cortical lesions, which decrease striatal glutamate uptake in synaptosome-containing homogenates by ∼50%, also decrease the striatal concentrations of the astrocytic glutamate transporter proteins, GLT-1 and GLAST by ∼20–30%. Since GABA uptake activity was not decreased and glial fibrillary acidic protein was increased in the same samples, the lesion-induced losses of GLT-1 and GLAST were not caused by a general impairment of neuronal or glial function. The observed reduction in the two astrocytic glutamate transporters after corticostriatal nerve terminal degeneration indicates that their levels of expression are dependent on glutamatergic innervation.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The distributions of the mRNAs encoding the l-glutamate transporters GLT1 and GLAST were examined in the rat brain by in situ hybridization using 35S-labelled oligonucleotide probes. Probes directed to GLT1 produced dense labelling in the hippocampus, neocortex and neostriatum, and weak labelling in the cerebellum. In contrast, GLAST mRNA appeared to be greatly enriched in the cerebellum compared to other brain regions. While the intensity of the labelling for GLAST and GLT1 varied among different regions, their cellular distributions appeared to coincide inasmuch as both mRNAs were mainly expressed by glial cells. Labelling occurred, inter alia, in glial cells throughout the hippocampus, and in Golgi epithelial cells in the Purkinje cell layer of the cerebellum.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 9 (1997), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The extracellular concentration of the excitatory neurotransmitter glutamate is kept low by the action of glutamate transporters in the plasma membranes of both neurons and glial cells. These transporters may play important roles, not only in the adult brain, but also in the developing brain, as glutamate is thought to modulate the formation and elimination of synapses as well as neuronal migration, proliferation and apoptosis. Here we demonstrate the developmental changes in the expression of two glutamate transporters, GLAST and GLT, by quantitative immunoblotting and by light and electron microscopic immunocytochemistry. At birth, GLT is not detectable, but GLAST is present at significant concentrations both in the forebrain and in the cerebellum. GLT is first detected in the forebrain and cerebellum in the second and third week, respectively. Both transporters reach adult levels by postnatal week 5. The development of the total glutamate uptake activity in the forebrain, as determined by solubilization and reconstitution of the transporters in liposomes, parallels that of GLT, in agreement with the observation that GLT is the predominant transporter in the adult brain. The regional distributions of both GLAST and GLT in the tissue are similar in young and adult rats. Only GLAST is detectable in the external germinal layer of the cerebellar cortex. Electron microscopical investigation demonstrated GLAST and GLT exclusively in glial cells in young as well as in adult animals.
    Type of Medium: Electronic Resource
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