Effects of dihydropyridine calcium-antagonists on intracellular action potentials of rabbit sinus node, atrium and atrioventricular node. Comparison of felodipine with nifedipine.
The effects of the new dihydropyridine Ca-antagonist felodipine (CAS 72509-76-3) (3 x 10(-9) mol/l - 10(-6) mol/l) on intracellular action potentials of the rabbit sinus node and atrium were studied. Results were compared to the effects of nifedipine (10(-8) mol/l - 3 x (-10) mol/l). Additionally, rate-dependent effects of both substances on AV nodal conduction time were assessed. The data demonstrate a concentration-dependent reduction of sinus nodal automaticity due to depression of phase 4 automaticity concomitant with a reduction of the maximum upstroke velocity of the sinus action potential by both substances. Felodipine was about one half order of magnitude more potent than nifedipine. Both substances exerted little effects on action potentials in atrial cells. Felodipine and nifedipine led to a concentration and frequency-dependent ("use-dependent") retardation of AV nodal conduction. Again felodipine was about one half order of magnitude more potent than nifedipine.
Beyer
T
T
Abteilung Innere Medizin III-Kardiologie, Ruprecht-Karls-Universität, Heidelberg, Fed. Rep. of Germany.
Brachmann
J
J
Kübler
W
W
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001283:Atrioventricular Node / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D015736:Felodipine / Q000494:pharmacology*; D005260:Female; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009431:Neural Conduction / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D009543:Nifedipine; D015736:Felodipine