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  • 1
    Digitale Medien
    Digitale Medien
    Release of N-Acetylaspartylglutamate on Depolarization of Rat Brain Slices (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: In a great number of investigations, evidence in favor of a neurotransmitter role of the N-terminal-blocked, acidic dipeptide N-acetylaspartylglutamate (NAAG) has been accumulating. In fact, in some systems of the mammalian brain, almost all of the classical criteria for neurotransmitters have been fulfilled by NAAG except for the demonstration of its release from nervous tissue on depolarization. For quantification of NAAG in superfusates of brain slices, we have developed an analytical procedure consisting of an ion exchange prepurification, followed by a derivatization procedure and gas chromatography-mass spectrometry with chemical ionization and selected ion monitoring. Deuterated NAAG was used as an internal standard to provide a high degree of reliability for the analytical method. Detection limits of 〈1 pmol were achieved. A statistically highly significant increase of NAAG concentration in superfusates from rat neocortex, piriform cortex/amygdala, and hippocampus on depolarization with 50 mM K+ could be demonstrated and was shown to be largely Ca2+ dependent. These results support the hypothesis that NAAG is a neurotransmitter. Especially with respect to the piriform cortex, the present demonstration of NAAG release is consistent with electrophysiological and immunohistochemical evidence for its neurotransmitter function at terminals of the lateral olfactory tract.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb01178.x
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  • 2
    Digitale Medien
    Digitale Medien
    Molecular Cloning and Differential Expression Patterns of Avian Glutamate Receptor mRNAs (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We have identified and studied potential ionotropic glutamate receptor genes in pigeon brain. Three cDNA clones exhibit significant amino acid sequence identity to members of a rodent ligand-gated ion channel family. One of them, GluP-II, encodes a full-length AMPA-sensitive glutamate receptor GluR2 (GluR-B) homologue, whereas the other two partial clones, designated as GluP-III and -IV, are nearly identical to rodent GluR3 (GluR-C) and GluR4 (GluR-D) receptor subunits. Northern analysis demonstrated that the avian genes are widely expressed in the brain. Within the brain regions analyzed by in situ hybridization histochemistry, the three avian GluR subunits showed distinct and regionally specific mRNA expression patterns in the adult. Most of the differences in their expression were observed in cell types of the telencephalon, certain thalamic nuclei, the optic tectum, and the cerebellar cortex. A particularly striking finding was the expression of GluP-II in Golgi epithelial/Bergmann glial cells. In contrast, Bergmann glial cells in rat cerebellum do not express GluR2 (GluR-B) subunit genes. Immunoreactivity for a monoclonal sequence-specific antipeptide antibody was widespread and most prominent in Purkinje cell perikarya and their dendrites, neuronal cell bodies of the ectostriatum, and the deep optic tectum. These results demonstrate the existence of multiple subunits of the ionotropic glutamate receptor channel family in avians. Excitatory amino acid receptor genes appear to be highly conserved during evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64062413.x
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  • 3
    Digitale Medien
    Digitale Medien
    In Vitro Release of Endogenous Excitatory Sulfur-Containing Amino Acids from Various Rat Brain Regions (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Efflux of various amino acids from rat brain slices was determined under resting or depolarizing conditions. Slices of neocortex, hippocampus, striatum, cerebellum, mesodiencephalon, pons-medulla, and spinal cord were depolarized by K+ (50 mM) or veratrine (33 μg/ml). The 4-N, N-dimethylamino-azobenzene-4′-isothiocyanate (DABITC) derivatization method of Chang [Biochem. J.199, 537–545 (1981)] for HPLC was adapted for analysis of amino acids and peptides in superfusion solutions. It allowed the separation and simultaneous detection of the sulfur-containing amino acids cysteine sulfinic acid (CSA), cysteic acid (CA), homocysteine sulfinic acid (HCSA), and homocysteic acid (HCA) at the picomole level. All four were shown to be released on depolarization in a Ca2+-dependent manner from brain slices. CSA and HCSA were released from cortex, hippocampus, mesodiencephalon, and, for HCSA only, striatum. HCA release, observed in all regions, was most prominent in cortex and hippocampus. CA was slightly increased by depolarization in hippocampus and mesodiencephalon. These sulfur-containing amino acids have been shown to exert an excitatory action on CNS neurons. The fact that these sulfur-containing amino acids are released as endogenous substances from nervous tissue supports the hypothesis that they play a role in CNS neurotransmission.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb13040.x
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  • 4
    Digitale Medien
    Digitale Medien
    Plasticity of Agonist Binding Sites in Hetero-Oligomers of the Unitary Glutamate Receptor Subunit XenU1 (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 71 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Two subunits from Xenopus, XenNR1G and the “short” subunit XenU1, have previously been coexpressed to form a unitary (NMDA/non-NMDA type) glutamate receptor. We now show that an antibody to XenNR1G or an antibody to XenU1 precipitates the binding sites of both XenNR1G and XenU1, with the recombinant subunits or with solubilised Xenopus brain membranes, i.e., the combination occurs in vivo. The expressed XenU1 subunits are in the cell membrane and oriented correctly. XenU1 binds not only kainate with high affinity (KD 1.2 nM at 25°C), but also the glycine site antagonist 5,7-dichlorokynurenic acid (DCKA). DCKA, GTP, or GTPγS displaces competitively all of the bound [3H]kainate, but glycine has no effect. The results suggest that a common binding site for kainate, DCKA, and GTP can exist on XenU1. In the XenNR1G/XenU1 complex, the kainate affinity is lowered eightfold, whereas the DCKA affinity is considerably increased (KD 147 nM). Only 18% of the binding to the complex has the properties of the NMDA receptor glycine site, the rest being due to switching of the high-affinity kainate site of XenU1 (low-affinity DCKA) to a high-affinity DCKA (low-affinity kainate) conformation. Surprisingly, a mammalian NR2 subunit can also combine with XenU1, and this introduces similar reciprocal changes in the binding of kainate and DCKA. The combined evidence suggests a common basic mode of agonist site formation in different subunit types of the ionotropic glutamate receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.71030991.x
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  • 5
    Digitale Medien
    Digitale Medien
    Glutamate-like Immunoreactivity in the Pigeon Optic Tectum and Effects of Retinal Ablation (1991)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 3 (1991), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The pattern of glutamate-like immunoreactivity was investigated in the pigeon optic tectum. The most impressive aspect of the labelling pattern was an accumulation of immunoreactive terminal-like elements restricted to those superficial tectal layers that correspond to the termination zone of the retinal afferents. These immunoreactive puncta occurred frequently in small clusters. At the level of electron microscopy, many of the labelled nerve endings showed the characteristics of retinal terminals. Moreover, following unilateral retinal ablation a drastic loss of immunoreactive terminal-like puncta was observed in the retinorecipient layers of the tectum contralateral to the lesion. The remaining glutamate-immunoreactive terminal-like elements had the light and electron microscopic features typical of the afferents from the nucleus isthmi, pars parvocellularis (lpc). The relation between the latter result and the transmitter specificity of the afferents from this subtectal nucleus is unclear at present. On the other hand, the light and electron microscopic labelling patterns and the effect of retinal ablation suggest that afferents from retina and from lpc are the only major sources for glutamate-immunoreactive terminals in the pigeon optic tectum. Furthermore, the results are well in line with previous data indicating glutamate as neurotransmitter at least in part of the retinal afferents to the pigeon optic tectum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1460-9568.1991.tb00824.x
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  • 6
    Digitale Medien
    Digitale Medien
    Homocysteate, an Excitatory Transmitter Candidate Localized in Glia (1991)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 3 (1991), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: l-Homocysteate, a sulphur-containing l-glutamate analogue has recently been proposed as a neurotransmitter candidate. However, the cellular localization of this excitatory amino acid remained to be determined. By means of immunocytochemistry, the localization of homocysteate was accomplished in the cerebellar cortex of rats. Cerebellar glia could be defined as the major store of this compound. Homocysteate, thus, may not be a classical neurotransmitter but rather a member of another class of intercellular messengers that might be termed ‘gliotransmitters’.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1460-9568.1991.tb00070.x
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  • 7
    Digitale Medien
    Digitale Medien
    Anatomical and Physiological Properties of GABAergic Neurotransmission in Organotypic Slice Cultures of Rat Hippocampus (1989)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 1 (1989), S. 0 
    Details
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The anatomical and physiological properties of GABAergic inhibitory neurotransmission were investigated in organotypic slice cultures of rat hippocampus. Interneurons and terminal-like elements containing GABA-like immunoreactivity were numerous in tissue kept for 13–26 days in culture and showed a similar morphology and distribution to those known from investigations on the hippocampal formation in situ. Furthermore, after 8–30 days in culture, spontaneous and evoked IPSPs were observed in all CA3 pyramidal cells tested, resulting from an increase in chloride conductance, and were shown to be mediated by activation of GABA receptors. No functional decrement in the efficacy of GABAergic inhibitory synaptic transmission following chronic isolation and long-term maintenance in vitro was noticed. In particular, neither the magnitude of the synaptic conductance underlying the inhibitory postsynaptic currents nor its reversal potential varied with time in culture. Taken together, the present physiological and immunohistochemical data show that GABAergic inhibition is well expressed in organotypic hippocampal slice cultures and is maintained over periods of at least 4 weeks in vitro.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1460-9568.1989.tb00366.x
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  • 8
    Digitale Medien
    Digitale Medien
    Neuronal and glial localization of homocysteate-like immunoreactivity in the rat retina (1994)
    Springer
    Journal of neurocytology 23 (1994), S. 783-791 
    Details
    ISSN: 1573-7381
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To study the distribution ofl-homocysteate in the rat retina, specific polyclonal and monoclonal anti-homocysteate antibodies have been used in combination with a highly sensitive postembedding method for light microscopic immunocytochemistry. In central and peripheral retina, the most strongly immunoreactive cell bodies lay in the inner nuclear layer. They represented about 17% of the total neuronal cell population of the layer and were identified as bipolar cells (19–20% of cells in the outer half of the inner nuclear layer) and amacrine cells (15% of cells in the inner half of the inner nuclear layer). A third cell type showing heavy homocysteate-like immunoreactivity was identified as Müller glial cells. Characteristically, their descending processes formed three immunoreactive bands in the inner plexiform layer. Furthermore, the outer and inner limiting membranes as well as glia around and between ganglion cell axons and in the vicinity of blood vessels were labelled intensely. Photoreceptors and their terminals, and ganglion cells, were not immunostained. These findings indicate the presence of homocysteate in some bipolar and amacrine cells of the inner nuclear layer and support a role for this sulphur-containing excitatory amino acid as a neurotransmitter candidate in the retina.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01268090
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