Effects of ethanol on cellular membrane potentials and contractility of isolated rat atrium

¹ Department of Pharmacology, University of Southern California School of Medicine, Los Angeles, California

The simultaneous effects of ethanol on the contractility and electrical characteristics of atrial cells were examined. Single cell membrane potentials were determined using microelectrodes; the mechanical activity was recorded from a sensitive strain gauge. Ethanol at concentrations between 24 and 192 mm (110–880 mg/100 ml) depresses the contractility of the rat atria, the relationship between contractile depression and concentration being essentially linear. The effects are reversible in all cases. A definite shortening of the action potential, simultaneous with the reduction in contractility, is the most characteristic change in the electrical properties. This results from a more rapid rate of repolarization. The magnitude of the action potential is decreased slightly, whereas the resting potential and the depolarization rate are unaffected by ethanol. The depression of the contractility can be partially attributed to the shortening of the action potential but, in addition, there would appear to be some more direct action on the contractile mechanism. The decrease in the duration of the action potential may predispose the atria to dysrhythmias, such as ectopic beats and fibrillation.

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