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  • 1
    Electronic Resource
    Electronic Resource
    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
    Keywords: Caffeine ; Methylxanthine ; Smooth muscle ; Calcium channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370755
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    Paper (German National Licenses)
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  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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