[Vagal influence in experimental arrhythmias caused by dopamine].

Dopamine induced cardiac arrhythmias in control and reserpine-treated rats which was successfully++ prevented by functional inhibition of the parasympathetic system. Both EKG and intracarotid mean blood pressure were recorded through a polygraph. Animals were anesthetized with urethane, intravenously heparinized and enhanced its spontaneous pulmonary ventilation with a tracheal cannula. Dopamine (50, 100, 200 and 400 micrograms/100 g,) produced cardiac arrhythmias characterized by atrioventricular block, ventricular premature depolarization and ventricular tachycardia. The parasympathetic inhibition resulting from bilateral vagotomy or atropine injection (1 mg/kg i.v.) induced a significant reduction in the arrhythmia frequency. A vagal reflex originating in great vessel baroreceptors is postulated as the ensuing mechanism. Vagal inhibition seems to be efficacious to prevent cardiac arrhythmias and lowering mortality rate.