Effects of low ethanol doses on heart rhythm in rabbits.

Effects of low ethanol doses on the vagosympathetic mechanisms of heart rhythm regulation were studied in rabbits. Analysis of heart rhythm variability showed that single intragastric administration of 0.5 mg/kg ethanol caused tachycardia in animals with initial predominance of vagal activity and bradycardia in animals with predominating sympathetic mechanisms. This was associated with general activation of all regulatory effects on the heart rhythm and a drastic increase in power spectrum for all frequency ranges, though with a certain deficiency of vagal effects. However, after 24 h the vagal component of the spectrum drastically increased in animals of both groups, while other parameters did not differ from the control. Presumably, this rebound can be used as a physiological marker, ethanol tolerance measure, formation of the abstinence syndrome and liability to alcoholism.