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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
    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)
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    The effects of varying the concentrations of ions in the external solution on the oscillations of the membrane potential (Slow Waves) produced by carbachol in longitudinal ileal muscle (1972)
    Springer
    Pflügers Archiv 335 (1972), S. 85-96 
    Details
    ISSN: 1432-2013
    Keywords: Smooth Muscle ; Slow Waves ; Carbachol ; Role of Ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The membrane potential of the cells of the longitudinal muscle of the guinea-pig ileum was recorded intracellularly with glass microelectrodes. Upon changing from isotonic physiological salt solution to sucrose hypertonic solution the spontaneous electrical activity of the membrane was abolished. Spike discharge, but not slow potential changes, was evoked by depolarizing current. In isotonic or in sucrose hypertonic solution, carbachol or acetylcholine caused spike discharge and produced oscillations of the membrane potential (slow waves) which, in hypertonic solution, were about 20 mV in size and 3 sec in duration. The effects on the response to carbachol of varying the ionic composition were examined in sucrose-hypertonic solution. Slow waves in response to carbachol were rapidly and reversibly abolished in sodium-deficient solution, though electrical stimulation evoked spikes for considerable periods. Slow waves were abolished also in sodium-free solution. In contrast, carbachol evoked slow waves after 20 min in calcium-free solution (in which the membrane depolarized) if the membrane was electrically repolarized. In chloride-deficient solution a small but significant (p〈0.05) increase occurred in the duration of slow waves evoked by carbachol. Carbachol elicited slow waves in potassium-free or in potassium-rich solution. The increases in slow wave size and duration in potassium-free solution fell short of statistical significance (0.1〉p〉0.05). The depolarization produced by carbachol was significantly (p〈0.05) less in sodium-deficient (15 mM) solution but was unaffected by alterations in the external chloride concentrations. In sodium-free solution, carbachol hyperpolarized the membrane. The results support a previous suggestion that the slow waves produced by acetylcholine or carbachol represent an inward sodium current through a slow regenerative ion channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592036
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    Paper (German National Licenses)
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