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  • 1
    Electronic Resource
    Electronic Resource
    SR 140333, a Novel, Selective, and Potent Nonpeptide Antagonist of the NK1 Tachykinin Receptor: Characterization on the U373MG Cell Line (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of a novel nonpeptide NK1 tachy-kinin receptor antagonist, SR 140333, on the functional consequences of NK1 receptor activation in a human astrocytoma cell line, U373MG, were investigated. Radioligand binding conducted with 125l-Bolton-Hunter substance P revealed a competitive inhibition by SR 140333 and its R enantiomer SR 140603 with Ki values of 0.74 and 7.40 nM, respectively. The NK1-selective agonist, [Sar9,Met(O2)11]-substance P, stimulated the formation of inositol phosphates with an EC50 of 3.8 × 10−9M. SR 140333 blocked the stimulatory effect of this agonist (10−7M) with an IC50 of 1.6 × 10−9M,whereas the effect of another NK1 agonist, septide (EC50= 1.5 × 10−8M)was antagonized with an IC50 of 2.1 × 10−10M.Enhancement of [3H]taurine release by [Sar9,Met(O2)11]-substance P (EC50= 7.4 × 10−9M) was also inhibited by SR 140333 with an IC50 of 1.8 × 10−9 M. SR 140603 was 10-fold less potent than SR 140333 in inhibiting inositol monophosphate formation and [3H]taurine release. The calcium mobilization induced by [Sar9,Met(O2)11]-substance P (10−8M) was totally prevented by 10−8MSR 140333. Patchclamp experiments showed that SR 140333 depressed the outward current evoked by 5 × 10−8M [Sar9, Met(O2)11]-substance P with an IC50 of 1.3 × 10−9M. The expression of c-fos was stimulated by [Sar9,Met(O2)11]-substance P with an EC50 of 2.5 × 10−10M, an effect that was also inhibited by SR 140333 with an IC50 of 1.1 × 10−9M. The present results illustrate the sequential events of the response elicited by NK1 agonists, which were antagonized by SR 140333, demonstrating its powerful NK1 antagonist activity on a functional basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62041399.x
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  • 2
    Electronic Resource
    Electronic Resource
    Chemokine modulation of high-conductance Ca2+-sensitive K+ currents in microglia from human hippocampi (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 18 (2003), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: During acute pathological processes, microglia transform into an activated state characterized by a defined morphology and current profile, and are recruited to injury sites by chemokines. No information is available on the ion channels and the mode of action of chemokines in microglia in brain slices from humans with a chronic pathology. Thus, patch-clamp recordings of microglia were performed in hippocampal slices from seven patients who underwent surgery for pharmaco-resistant epilepsy. Cells were identified as microglia by positive labelling with fluorescein-conjugated tomato lectin before recording. All the recorded cells had an ameboid morphology characteristic of activated microglia. However, they had a high input resistance (3.6 GΩ), a zero-current resting potential of −16 mV, and lacked Na+ currents, inwardly rectifying and delayed rectifying K+ currents such as non-activated microglia. Importantly, recorded cells expressed Ca2+-sensitive outward currents that activated at 0 mV with non-buffered intracellular Ca2+ and were sensitive to 1 mm tetraethylammonium (TEA). The estimated single-channel conductances were 187 pS in cell-attached and 149 pS in outside-out patches, similar to those of high-conductance Ca2+-dependent K+ channels. The chemokine MIP1-α increased whole-cell outward current amplitudes measured at +60 mV by a factor of 3.3. Thus, microglia in hippocampi from epileptic patients express high-conductance Ca2+-dependent K+ channels that are modulated by the chemokine MIP1-α. This modulation may contribute to the migratory effect of MIP1-α on microglia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2003.03021.x
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  • 3
    Electronic Resource
    Electronic Resource
    Actions of nicotinic agonists on the intermediolateral nucleus neurons in the neonate rat spinal cord in vitro
    Amsterdam : Elsevier
    Journal of Physiology-Paris 88 (1994), S. 374 
    Details
    ISSN: 0928-4257
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0928-4257(94)90040-X
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  • 4
    Electronic Resource
    Electronic Resource
    Muscarinic Activation of BK Channels Induces Membrane Oscillations in Glioma Cells and Leads to Inhibition of Cell Migration (2000)
    Springer
    The journal of membrane biology 176 (2000), S. 31-40 
    Details
    ISSN: 1432-1424
    Keywords: Key words: BK channels — Muscarine — Acetylcholine — Calcium — Migration — Tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Patients with cerebral tumors often present with elevated levels of acetylcholine (ACh) in their cerebrospinal fluid. This motivated us to investigate physiological effects of ACh on cultured human astrocytoma cells (U373) using a combination of videomicroscopy, calcium microspectrofluorimetry and perforated patch-clamp recording. Astrocytoma cells exhibited the typical morphological changes associated with cell migration; polarized cells displayed prominent lamellipodia and associated membrane ruffling at the anterior of the cell, and a long tail region that periodically contracted into the cell body as the cell moved forward. Bath application of the ACh receptor agonist, muscarine, reversibly inhibited cell migration. In conjunction with this inhibition, ACh induced a dose-dependent, biphasic increase in resting intracellular free calcium concentration ([Ca2+] i ) associated with periodic Ca2+ oscillations during prolonged ACh applications. The early transient rise in [Ca2+] i was abolished by ionomycin and thapsigargin but was insensitive to caffeine and ryanodine while the plateau phase was strictly dependent on external calcium. The Ca2+ response to ACh was mimicked by muscarine and abolished by the muscarinic antagonists, atropine or 4-DAMP, but not by pirenzepine. Using perforated patch-clamp recordings combined with fluorescent imaging, we demonstrated that ACh-induced [Ca2+] i oscillations triggered membrane voltage oscillations that were due to the activation of voltage-dependent, Ca2+-sensitive K+ currents. These K+ currents were blocked by intracellular injection of EGTA, or by extracellular application of TEA, quinine, or charybdotoxin, but not by apamin. These studies suggest that activation of muscarinic receptors on glioma cells induce the release of Ca2+ from intracellular stores which in turn activate Ca2+-dependent (BK-type) K+ channels. Furthermore, this effect was associated with inhibition of cell migration, suggesting an interaction of this pathway with glioma cell migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00232001073
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  • 5
    Electronic Resource
    Electronic Resource
    Passive Glial Cells, Fact or Artifact? (1998)
    Springer
    The journal of membrane biology 166 (1998), S. 213-222 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Patch-clamp — Slices — Astrocyte — Voltage-activated channels — Potassium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Astrocytes that are recorded in acute tissue slices of rat hippocampus using whole-cell patch-clamp, commonly exhibit voltage-activated Na+ and K+ currents. Some reports have described astrocytes that appear to lack voltage-activated currents and proposed that these cells constitute a subpopulation of electrophysiologically passive astrocytes. We show here that these cells can spontaneously change during a recording unmasking expression of previously suppressed voltage-activated currents, suggesting that such cells do not represent a subpopulation of passive astrocytes. Superfusion of a low Ca2+/EGTA solution was able to reversibly suppress voltage-activated K+ currents in cultured astrocytes. Currents were restored upon addition of normal bath Ca2+. These effects of Ca2+ on both outward and inward K+ currents were dose- and time-dependent, with increasing concentrations of Ca2+ (from 0 to 800 μm) leading to a gradual unmasking of voltage-dependent outward and inward K+ currents. The transition from an apparently passive cell to one exhibiting prominent voltage-activated currents was not associated with any changes in membrane capacitance or access resistance. By contrast, in cells in which low access resistance or poor seal accounted for the absence of voltage-activated currents, improvement of cell access was always accompanied by changes in series resistance and membrane capacitance. We propose that spillage of pipette solution containing low Ca2+/EGTA during cell approach in slice recordings and/or poor cell access, lead to a transient masking of voltage-activated currents even in astrocytes that express prominent voltage-activated currents. These cells, however, do not constitute a subpopulation of electrophysiologically passive astrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900463
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