Arrhythmogenic effects of digoxin were studied in guinea pig ventricular myocardium driven at a low frequency, using microelectrode technique. Prolonged exposure to digoxin made two distinct phases of arrhythmias to appear: the first phase early occurred without apparent alteration in membrane diastolic potential of the impaled ventricular cells, the second phase was later initiated from oscillatory afterpotentials in diastolic potential. It is proposed that phase 1 of arrhythmias is initiated from oscillatory afterpotentials generated in Purkinje fibers more sensitive to digoxin-induced arrhythmogenic effects than myocardial cells. Phase 2 of arrhythmias would be originated in ventricular muscle fibers. Caffeine abolished oscillatory afterpotentials and suppressed sustained rhythmical activities of phases 1 and 2. The results indirectly confirm the important role of calcium movements between the myoplasm and sarcoplasmic reticulum in the origin of digoxin-induced arrhythmias triggered by oscillatory afterpotentials.
Download full-text PDF |
Source |
|---|
Publication Analysis
Top Keywords
Similar Publications
Novel oscillatory mechanisms in the cholinergic control of Guinea pig sino-atrial node discharge.
J Cardiovasc Electrophysiol
January 2011
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.
Unlabelled: Oscillatory Mechanisms in Sinus Node Cholinergic Control.
Introduction: The role of the oscillatory after-potential V(os) and pre-potential ThV(os) in cholinergic control of discharge was studied in sino-atrial node (SAN).
Methods And Results: A microelectrode technique was used in isolated guinea-pig SAN superfused in vitro in high [K(+) ](o) to visualize V(os) and ThV(os) .
Essential role of diastolic oscillatory potentials in adrenergic control of guinea pig sino-atrial node discharge.
J Biomed Sci
November 2009
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.
Background: The diastolic oscillatory after-potential Vos and pre-potential ThVos play an essential role in the pacemaker mechanism of sino-atrial node (SAN). The aim of this study was to investigate whether these oscillatory potentials are also involved in adrenergic control of SAN discharge.
Methods: Vos and ThVos were visualized by superfusing guinea pig SAN in high [K+]o.
The effects of isoproterenol on abnormal electrical and contractile activity and diastolic calcium are attenuated in myocytes from aged Fischer 344 rats.
Mech Ageing Dev
October 2007
Department of Pharmacology, Sir Charles Tupper Medical Building, Dalhousie University, 5850 College St., Halifax, Nova Scotia, Canada B3H 1X5.
We investigated whether the age-related decrease in sensitivity of the heart to catecholamines was accompanied by changes in Ca(2+) homeostasis and abnormal electrical and contractile activity caused by beta-adrenergic receptor (beta-AR) stimulation. Ventricular myocytes were isolated from young adult (3 months) and aged (24 months) male Fischer 344 rats. Unloaded cell shortening was measured in field-stimulated myocytes (2Hz, 37 degrees C); membrane currents and action potentials were measured with microelectrodes.
View Article and Find Full Text PDFOn the mechanisms underlying diastolic voltage oscillations in the sinoatrial node.
J Electrocardiol
July 2006
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.
Aim: The study of the mechanisms underlying the oscillatory afterpotential (V(os)) and prepotential (ThV(os)).
Background: It has been recently shown that V(os) and ThV(os) play an obligatory role in the dominant sinoatrial node (SAN) discharge.
Methods: Guinea pig isolated SAN was studied in vitro by means of a microelectrode technique.
Temperature regulates the arrhythmogenic activity of pulmonary vein cardiomyocytes.
J Biomed Sci
April 2004
Institute of Pharmacology and Physiology, Taipei Medical University, Wan-Fang Hospital, Taipei, Taiwan.
Temperature plays an important role in the electrophysiology of cardiomyocytes. Pulmonary veins (PVs) are known to initiate paroxysmal atrial fibrillation. The effects of temperature on the arrhythmogenic activity of rabbit single PV and atrial cardiomyocytes were assessed using the whole-cell clamp technique.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!