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  • 1
    Electronic Resource
    Electronic Resource
    The mechanism of action of Ba2+ and TEA on single Ca2+-activated K+-channels in arterial and intestinal smooth muscle cell membranes (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 120-127 
    Details
    ISSN: 1432-2013
    Keywords: Smooth muscle ; Ba2+ ; TEA ; Ca2+-activated K+ channels ; Patchclamp ; Channel block
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The interaction of Ba2+ and TEA with Ca2+-activated K+ channels was studied in isolated membrane patches of cells from longitudinal jejunal smooth muscle of rabbit and from guinea-pig small mesenteric artery (100 μm external diameter). Ba2+ applied from the inside of the membrane did not reduce unit current, except at high concentrations, but channels failed to open for long periods (s). This effect became much stronger when the potential gradient was in a direction driving Ba2+ into the channel and was reduced by increasing K+ ion concentration on the outside of the membrane. These results are consistent with Ba2+ entering the open channel and blocking at a site most of the way through the channel bore. In contrast, TEA and procaine dose-dependently reduced unit current amplitude at all patch potentials and slightly increased mean open time. Their effects were not detectably voltage-dependent and could be explained by TEA and procaine blocking the open channel with a timecourse that was faster than the frequency response of the recording system. The lack of appreciable voltage-dependence suggests that TEA and procaine bind to a site near to the inner mouth of the channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584088
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Oscillations of receptor-operated cationic current and internal calcium in single guinea-pig ileal smooth muscle cells (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 431-438 
    Details
    ISSN: 1432-2013
    Keywords: Calcium oscillations ; Muscarinic receptor ; Calcium stores ; G protein ; Heparin ; Ryanodine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In single cells isolated from guinea-pig ileal smooth muscle, held under voltage clamp at −40 mV or −50 mV by patch pipette in the whole-cell recording mode, carbachol (CCh) evoked an oscillatory inward cationic current. The frequency of current oscillations increased with increasing CCh concentration. CCh-evoked current oscillations were followed very closely by oscillations in intracellular free Ca2+ estimated from the Indo-1 signal, and were abolished by inclusion of EGTA in the pipette solution. Ryanodine and heparin, but not nifedipine, blocked the generation of current oscillations. CCh-evoked current oscillations were abolished upon withdrawal of extracellular calcium and restored upon its reintroduction. Inclusion of GTP[γS] in the pipette solution caused the generation of an oscillatory inward current, which was blocked by ryanodine. The present results are consistent with the hypothesis that CChevoked cationic current is gated by activation of a G protein and is steeply dependent on [Ca2+]i, fluctuations in the release of Ca2+ from stores during carbachol's action produce oscillations in [Ca2+]i which cause similar oscillations in the cationic current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374905
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Inositol trisphosphate releases stored calcium to block voltage-dependent calcium channels in single smooth muscle cells (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 437-441 
    Details
    ISSN: 1432-2013
    Keywords: Inositol trisphosphate ; Caged InsP 3 ; Caged ATP ; Heparin ; Calcium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In single cells obtained by enzymic treatment of rabbit small-intestinal smooth muscle, and held under voltage clamp by patch pipette in the whole-cell recording mode, release of inositol trisphosphate (InsP 3) from its caged precursor by flash photolysis caused complete inhibition of the voltage-dependent calcium current. No inhibition was seen in control experiments where the cage (2-nitrosoacetophenone) was released by flash photolysis from caged ATP. The inhibition by InsP 3 of the calcium current was prevented if 10 mM EGTA or 2 mg/ml heparin was included in the pipette solution. Heparin is known to block InsP 3 receptors. These results suggest that release of calcium stores by InsP 3 raises Cai and that calcium ions inhibit the calcium current by acting either directly or otherwise on the internal mouth of the calcium channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00497770
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    Paper (German National Licenses)
    Fulltext
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