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  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Smooth muscle ; Ba2+ ; TEA ; Ca2+-activated K+ channels ; Patchclamp ; Channel block
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00584088
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    The action of caffeine on inward barium current through voltage-dependent calcium channels in single rabbit ear artery cells (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 462-466 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Caffeine ; Methylxanthine ; Smooth muscle ; Calcium channel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of caffeine on inward current carried by barium ions through voltage-dependent calcium channels has been investigated in single rabbit ear artery cells using whole-cell voltage-clamp techniques. Caffeine (1 –30 mM) caused a rapid and reversible concentration-dependent blockade of barium current and a related compound, 3-isobutyl-1-methylxanthine (IBMX), was a more potent inhibitor of barium current. Caffeine-induced inhibition of barium current showed no voltage- or usedependence and caffeine did not alter the steady-state inactivation of barium current. The effect of caffeine was not blocked by extracellular or by intracellular ryanodine or inclusion of both 5 mM 1,2-bis(2-aminophenoxy)-ethane N,N,N′,N′,-tetraacetic acid (BAPTA) and 2 mM ethylene glycol-bis(β-amino ethyl ether) N,N,N′,N′,-tetraacetic acid (EGTA) in the intracellular solution. Rolipram and M&B 22984, non-xanthine inhibitors of phosphodiesterase, did not diminish inward barium current. The data indicate that caffeine and IBMX block voltage-operated calcium channels and it is suggested that this is due to a direct interaction of methylxanthines with the calcium channel.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00370755
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Calcium oscillations ; Muscarinic receptor ; Calcium stores ; G protein ; Heparin ; Ryanodine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00374905
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