With the use of normotensive laboratory Wistar strain rats, changes in heart rate induced by three newly synthesized potential ultrashort beta-blockers were tested. The animals were administered the tested substances intravenously in general anesthesia. In all animals, heart rate was measured at predetermined time intervals. All obtained values were converted into the per cents of the heart rate deviation and the results were statistically processed. Using F-test, variability of dispersion was determined, and using Student t-test, statistical significance of the particular change was determined. In all three substances tested, a statistically demonstrable short-time bradycardiac effect was observed. The most marked decrease took place in the first minute after intravenous administration. Substance 44Bu induced the significantly deepest decrease in heart rate (by 13.00%), which lasted longest. No statistically significant difference was found between the actions of substances 42Bu and 43Bu. In all three substances tested, marked changes in the ECG record were observed immediately after intravenous administration. PQ and QT intervals and QRS complex were prolonged, and marked S wave, elevation of the T wave, and a decrease in R wave occurred. The changes were accompanied by a change in the electric cardiac axis.

        Key words: ultrashort-acting beta-blockers – heart rate – changes in ECG – ion channels