The rest-dependent depression of action potential duration in rabbit myocardium and the possible role of the transient outward current. A pharmacological analysis.
A pharmacological approach has been used to investigate the mechanism of the action potential depression after a 1 min rest in rabbit myocardium. This paradoxical depression was not prevented by potentiators of the slow inward current (isoproterenol and 5'-guanylylimidodiphosphate). This depression was completely removed by a specific blocker of the transient outward current, 4-aminopyridine. It appears reasonable to assume that rabbit ventricular fibers have a transient outward current and the activation of this current coupled to the masking of the slow inward current probably accounts for the depression of the rested action potential plateau phase.
D000200:Action Potentials / Q000187:drug effects; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003864:Depression, Chemical; D004558:Electric Stimulation; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D007097:Imines / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012146:Rest; D013997:Time Factors; D014044:Tolbutamide / Q000494:pharmacology
D000631:Aminopyridines; D007097:Imines; D007473:Ion Channels; D006165:Guanylyl Imidodiphosphate; C014925:RMI 12330A; D014044:Tolbutamide; D007545:Isoproterenol; D011188:Potassium; D002118:Calcium