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  • 1
    Electronic Resource
    Electronic Resource
    Cannabinoids inhibit hippocampal GABAergic transmission and network oscillations (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Using a new antibody developed against the C-terminus of the cannabinoid receptor (CB1), the immunostaining in the hippocampus revealed additional axon terminals relative to the pattern reported previously with an N-terminus antibody. Due to a greater sensitivity of this antibody, a large proportion of boutons in the dendritic layers displaying symmetrical (GABAergic) synapses were also strongly immunoreactive for CB1 receptors, as were axon terminals of perisomatic inhibitory cells containing cholecystokinin. Asymmetrical (glutamatergic) synapses, however, were always negative for CB1. To investigate the effect of presynaptic CB1 receptor activation on hippocampal inhibition, we recorded inhibitory postsynaptic currents (IPSCs) from principal cells. Bath application of CB1 receptor agonists (WIN55,212-2 and CP55,940) suppressed IPSCs evoked by local electrical stimulation, which could be prevented or reversed by the CB1 receptor antagonist SR141716A. Action potential-driven IPSCs, evoked by pharmacological stimulation of a subset of interneurons, were also decreased by CB1 receptor activation. We also examined the effects of CB1 receptor agonists on Ca2+-independent miniature IPSCs (mIPSC). Both agonists were without significant effect on the frequency or amplitude of mIPSCs. Synchronous gamma oscillations induced by kainic acid in the CA3 region of hippocampal slices were reversibly reduced in amplitude by the CB1 receptor agonist CP 55,940, which is consistent with an action on IPSCs. We used CB1–/– knock-out mice to confirm the specificity of the antibody and of the agonist (WIN55,212-2) action. We conclude that activation of presynaptic CB1 receptors decreases Ca2+-dependent GABA release, and thereby reduces the power of hippocampal network oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00217.x
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  • 2
    Electronic Resource
    Electronic Resource
    Calbindin-D28K (CaBP) levels and calcium currents in acutely dissociated epileptic neurons (1991)
    Springer
    Experimental brain research 85 (1991), S. 543-551 
    Details
    ISSN: 1432-1106
    Keywords: Voltage-dependent Ca2+-currents (HVA or L-type) ; Inactivation ; Intraneuronal Ca2+ ; Buffering ; Dentate gyrus granule cells ; Kindling-induced epilepsy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nerve cells that lack the cytoplasmic Ca2+ binding protein Calbindin-D28K (CaBP) appear to be selectively vulnerable to Ca2+-related injury consistent with a postulated intraneuronal Ca2+-buffering role of CaBP. We have confirmed the selective loss of CaBP from the dentate gyrus during kindling-induced epilepsy in acutely dissociated granule cells (GCs) from kindled rats. Immunohistochemically stained kindled neurons showed a significant loss of CaBP when compared to controls (p 〈 0.001; ANOVA). The Ca2+-buffering role of CaBP was assessed in acutely dissociated control and kindled GCs by examining a physiological process highly sensitive to intracellular Ca2+-buffering: the Ca2+ -dependent inactivation of high-voltage activated (HVA or L-type) Ca2+ currents in the absence (or presence) of exogenous Ca2+-chelators. Whole-cell patch clamp recordings in kindled GCs demonstrated a markedly enhanced Ca2+-dependent inactivation of Ca2+-currents. After brief conditioning Ca2+ currents, in the absence of an exogenous intraneuronal Ca2+-chelator, subsequent test Ca2+ currents were inactivated by 58.3% in kindled GCs, a significant increase from the 37.4% inactivation observed in control GCs (p〈 0.005; ANOVA). The differential Ca2+ current decay and Ca2+-dependent inactivation were prevented in both control and kindled GCs upon loading the neurons with the exogenous Ca2+-chelator BAPTA. These experiments demonstrate a high correlation between the loss of CaBP and changes in Ca2+ current inactivation and are consistent with the hypothesis that CaBP contributes to the physiological Ca2+-buffering in mammalian neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231738
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  • 3
    Electronic Resource
    Electronic Resource
    A role for N-methyl-D-aspartate receptors in norepinephrine-induced long-lasting potentiation in the dentate gyrus (1989)
    Springer
    Experimental brain research 77 (1989), S. 517-530 
    Details
    ISSN: 1432-1106
    Keywords: Calcium ; Dentate gyrus ; Hippocampus ; Ion-selective microelectrodes ; Long-term potentiation ; N-methyl-D-aspartate ; Norepinephrine ; Plasticity ; Quisqualate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mechanisms of action of norepinephrine (NE) on dentate gyrus granule cells were studied in rat hippocampal slices using extra- and intracellular recordings and measurements of stimulus and amino acid-induced changes in extracellular Ca2+ and K+ concentration. Bath application of NE (10–50 μM) induced long-lasting potentiation of perforant path evoked potentials, and markedly enhanced high-frequency stimulus-induced Ca2+ influx and K+ efflux, actions blocked by β-receptor antagonists and mimicked by β agonists. Enhanced Ca2+ influx was primarily postsynaptic, since presynaptic Δ [Ca2+]0 in the stratum moleculare synaptic field was not altered by NE. Interestingly, the potentiation of both ionic fluxes and evoked population potentials were antagonized by the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (APV). Furthermore, NE selectively enhanced the Δ[Ca2+]0, Δ[K+]0 and extracellular slow negative field potentials elicited by iontophoretically applied NMDA, but not those induced by the excitatory amino acid quisqualate. These results suggest that granule cell influx of Ca2+ through NMDA ionophores is enhanced by NE via β-receptor activation. In intracellular recordings, NE depolarized granule cells (4.8±1.1 mV), and increased input resistance (RN) by 34±6.5%. These actions were also blocked by either the β-antagonist propranolol or specific β 1-blocker metoprolol. Moreover, the depolarization and RN increase persisted for long periods (93±12 min) after NE washout. In contrast, while NE, in the presence of APV, still depolarized granule cells and increased RN, APV made these actions quickly reversible upon NE washout (16±9 min). This suggested that NE induction of long-term, but not short-term, plasticity in the dentate gyrus requires NMDA receptor activation. NE may be enhancing granule cell firing by some combination of blockade on the late Ca2+-activated K+ conductance and depolarization of granule cells, both actions that can bring granule cells into a voltage range where NMDA receptors are more easily activated. Furthermore, NE also elicited activity-independent long-lasting depolarization and RN increases, which required functional NMDA receptors to persist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249605
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  • 4
    Electronic Resource
    Electronic Resource
    Mammalian neurons in dissociated cultures form clusters in the presence of retinal pigment epithelium (1991)
    Springer
    Experimental brain research 83 (1991), S. 643-655 
    Details
    ISSN: 1432-1106
    Keywords: Retina ; Cytoarchitecture ; Development ; Retinal pigment epithelium ; Mouse ; Cats ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The objective of this study was to investigate the cellular processes involved in the formation of the cytoarchitectonics of the retina. Neurons derived from the retina, spinal cord, cerebral cortex and hippocampus were grown in dissociated monolayer tissue culture using standard techniques. The cultures of retina were unique in that the neurons actively formed into itcell clusters. On the other hand, cultures of neurons from the other regions of the CNS grew without forming any obvious histotypical pattern. Cell clusters consisted of an apparent monolayer of neurons above a population of flat cells and clusters were observed in retinal cultures derived from all species studied (mouse, cat and guinea pig). Each cluster was surrounded by whorls of fibroblasts; astrocytes (GFAP-positive cells) were often closely associated with clusters. Formation of clusters appeared to depend strongly upon the presence of cells derived from the retinal pigment epithelium (RPE) because the ability of retinal cells to form clusters was markedly impaired when the RPE was omitted from the cultures. Interestingly, monolayer cultures of neurons from other regions of the CNS could be induced to form clusters, but only when cells of the RPE layer were included at the time of plating. In cultures grown without the RPE layer, clusters did not form when media taken from cultures expressing clusters was used, indicating that the formation of clusters was not caused by a mediabourne factor. On the other hand, clusters did form when neurons without RPE were grown on feeder plates in which clusters had previously been expressed and the neurons subsequently killed by prolonged culturing or by treatment with kainic acid. Hence, physical contact between neurons and cells derived from the RPE appears critical for the formation of clusters. Our results suggest that the cellular processes underlying the formation of clusters may reflect those in the development of the retina in vivo. Thus, cluster formation may be a useful model for investigating the initial stages in the development of retinal cytoarchitecture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229842
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  • 5
    Electronic Resource
    Electronic Resource
    Development and characterization of cellulose acetate benzoate flat osmotic membranes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1031-1035 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Different parameters of casting solutions and casting conditions were studied for the development of cellulose acetate benzoate flat osmotic membranes. Casting solutions were prepared with different concentrations of the polymer, the additive, and the solvent; viscosity of the casting solution; and the thickness of the membrane developed. The membranes were given different evaporation periods and annealing temperatures under different RH. Different annealing baths were also used. Based on these, conditions were optimized for the development of cellulose acetate benzoate flat osmotic membranes. These membranes were characterized with respect to bound water content, specific water content, transport properties by direct osmosis, salt intake by direct immersion, water permeability coefficient of the dense membrane, diffusion coefficient, salt permeability, and salt distribution by electrical conductivity. Also, cellulose acetate benzoate membranes were compared with conventionally used cellulose acetate membranes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 14 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520804
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