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  • 1
    Electronic Resource
    Electronic Resource
    MECHANISMS UNDERLYING THE CARDIOVASCULAR ACTION OF A NEW DIHYDROPYRIDINE VASODILATOR, YC-93 (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 7 (1980), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1.The mechanisms underlying the cardiovascular action of YC-93, a new dihydropyridine vasodilator with cyclic AMP phosphodiesterase inhibitory activity, was investigated by comparing its effects wth those of papaverine in various isolated, blood-perfused heart preparations of the dog.2. In all preparations YC-93 injected into the nutrient arteries produced a dose-dependent increase in blood flow, and in this respect YC-93 was about twenty times more potent than papaverine on a weight basis.3. In sinoatrial node preparations YC-93 injected into the sinus node artery decreased sinus rate in a dose-dependent manner, and in large doses produced atrial standstill.4. In atrioventricular (a.v.) node preparations YC-93 injected into the a.v. node artery increased a.v. conduction time in a dose-dependent manner, and in large doses produced a second or third degree block of a.v. conduction. However YC-93 injected into the anterior septal artery scarcely affected a.v. conduction.5. In spontaneously contracting papillary muscle preparations YC-93 injected into the anterior septal artery failed to affect ventricular automaticity in doses which markedly decreased developed tension of papillary muscles.6. In papillary muscle preparations driven at a fixed rate YC-93 injected into the anterior septal artery produced a dose-dependent decrease in developed tension of papillary muscles.7. Unlike YC-93, papaverine decreased a.v. conduction time in a.v. node preparations and increased developed tension of papillary muscle preparations.8. The cardiac effects of YC-93 elucidated in the present experiments are characteristic of calcium-antagonistic vasodilators. The action of YC-93 as an inhibitor of cyclic AMP phosphodiesterase does not appear to play a role in its cardiac action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1980.tb00069.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of 2-nicotinamidethyl nitrate (SG-75) on the membrane potential of left atrial muscle fibres of the dog (1980)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 312 (1980), S. 69-76 
    Details
    ISSN: 1432-1912
    Keywords: 2-Nicotinamidethyl nitrate (SG-75) ; Methacholine ; Membrane potential ; Atrial muscle ; Potassium conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. 2-Nicotinamidethyl nitrate (SG-75) (10−6–10−4 mol/l) and methacholine (MeCh) (10−7–10−5 mol/l) hyperpolarized the resting membrane potential, and produced increases in amplitude and maximum rate of rise and a decrease in duration of the action potential of left atrial muscle fibres of the dog. 2. Changes in membrane potentials produced by SG-75 were not modified by atropine at a concentration (3×10−7 mol/l) which greatly antagonized those induced by MeCh. 3. The decrease in resting membrane potential for a 10-fold increase in extracellular K+ concentration ([K+]0) was greater in the presence than in the absence of SG-75 or MeCh. 4. SG-75- and MeCh-induced changes in membrane potentials were not affected by the replacement of NaCl by Na isethionate in perfusion fluid. 5. SG-75- and MeCh-induced changes in membrane potentials were not modified by ouabain (10−6 mol/l). 6. The “slow response” of left atrial muscle fibres was obtained by increasing the [K+]0 to 27 mM in the presence of isoprenaline (10−6 mol/l). SG-75 and MeCh primarily produced a decrease in duration of the “slow response”. At higher concentrations SG-75 and MeCh hyperpolarized the resting membrane potential and decreased the amplitude and maximum rate of rise of the “slow response”. Unlike SG-75 and MeCh, verapamil primarily decreased the amplitude and maximum rate of rise of the “slow response” without changes in duration of the “slow response” and resting membrane potential. 7. The above results suggest that the mechanism of action of SG-75 on left atrial muscle fibres may be an increase in potassium conductance of the membrane without mediation through muscarinic receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502577
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    Paper (German National Licenses)
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