In tests on cats with cut vagus and aortal nerves, clipped common carotid arteries caused a sharp increase in sympathic activity (SA) in the cardiac nerves, a rise of arterial pressure (AP) and ventricular arrhythmias. Lithium chloride and hydroxibutirate injected intravenously reduced SA, AP and restored sinus rhythm. While administering arrhythmogenic doses of strophantin R, similar rhythm disturbances were observed in addition to increase in SA in animals with denervated cardio-aortal and sinocarotid areas. In these cases lithium drugs also had an antiarrhythmic action and reduced SA. In cats with the preserved innervation of the above reflexogenic sites, reflexogenic sites, strophantine arrythmias developed against the background of SA reduction and lithium drugs were inefficacious. In experiments on rats, while injecting large doses of intravenous adrenalin secondary ventricular rhythm disturbances have been shown to occur 1-1.5 min after the drug injection and to result in death, Lithium chloride and hydroxibutirate prevent the development of these arrhythmias and the animals' death.