Cardiovasc Res. 1988 Jun;22(6):375-84. doi: 10.1093/cvr/22.6.375.

Comparative effects of three class I antiarrhythmic drugs on plateau and pacemaker currents of sheep cardiac Purkinje fibres.

Cardiovascular research

E Coraboeuf, E Deroubaix, D Escande, A Coulombe

PMID: 2852055 DOI: 10.1093/cvr/22.6.375

Abstract

The electrophysiological effects of three class I antiarrhythmic drugs, lignocaine, disopyramide, and penticainide, were compared in sheep cardiac Purkinje fibres. Action potential duration was shortened with all three drugs, the effect being small with disopyramide, moderate with penticainide, and greatest with lignocaine. Slowing down of the early phase of repolarisation was greatest with disopyramide, smaller with penticainide, and did not occur with lignocaine. Automaticity recorded in low potassium media was unaltered (disopyramide), depressed (penticainide), or stopped (lignocaine). Ionic currents were recorded in short fibres using the two microelectrode voltage clamp technique. The tetrodotoxin sensitive slow component of the sodium current was suppressed (lignocaine) or reduced (penticainide and disopyramide) and the instantaneous background potassium current slightly reduced (disopyramide more than penticainide), unaffected, or slightly increased (lignocaine). The three drugs depressed moderately and similarly the slow inward calcium current. The amplitude of the 4-aminopyridine sensitive transient outward potassium current was almost unaffected (lignocaine) or appreciably depressed (disopyramide more than penticainide). The pacemaker current was reduced greatly by lignocaine, moderately by penticainide, and slightly by disopyramide. Changes in ionic currents may explain the effects of the three drugs on action potential plateau and automaticity of sheep Purkinje fibres. It is concluded that the pronounced differences observed in the effects of these three class I antiarrhythmic drugs on pacemaker depolarisation and on initial repolarisation may justify a more discriminative subdivision of class I antiarrhythmic drugs.

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Substances

• Anti-Arrhythmia Agents
• Calcium Channels
• Potassium Channels
• Propylamines
• Pyridines
• Sodium Channels
• Tetrodotoxin
• propisomide
• Lidocaine
• Disopyramide

MeSH terms

• Action Potentials / drug effects
• Animals
• Anti-Arrhythmia Agents / pharmacology
• Calcium Channels / drug effects
• Disopyramide / pharmacology
• Heart Conduction System / drug effects
• Lidocaine / pharmacology
• Membrane Potentials / drug effects
• Potassium Channels / drug effects
• Propylamines / pharmacology
• Purkinje Fibers / drug effects
• Pyridines*
• Sheep
• Sodium Channels / drug effects
• Tetrodotoxin / pharmacology

Publication Types

• Comparative Study
• Journal Article
• Research Support, Non-U.S. Gov't

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