Role of the parasympathetic nervous system in alcohol-induced bradycardia in conscious cats.

The influence of intracardial injection of ethanol into the right atrium was studied in 10 unanaesthetized unrestrained cats. The initial effect of the injection was bradycardia with nonsignificant decreases in mean carotid artery pressure (APm) or increases in mean right atrial pressure (RAPm). The same was evident in HR and APm with animals pretreated with a beta-blocking agent. Bradycardia could not be introduced in atropinized cats or ones treated with atropine and beta-blocking agent. We conclude that bradycardia is elicited mainly by the influence of ethanol stimulating the vagal centres of the central nervous system (CNS), but the direct influence of ethanol to the heart cannot be excluded.