Effects of high doses of ouabain on cardiac, respiratory, and motor activity at newborn rats

Abstract

BACKGROUND: In the early postnatal period, the activation of cholinergic regulation was shown to reveal that lead to development of atypical cardiac rhythm in form of alteration of normal and weak bradycardic rhythm and periods of significant bradycardia. AIM: To study the change in the rhythmic activity of cardiac, respiratory and somatomotor systems after Na+/K+-ATPase blockade by ouabain in rats of 3 and 16 days old MATERIALS AND METHODS: In 3- (P3) and 16-day-old (P16) rats the change in the rhythmic activity of cardiac, respiratory and somatomotor systems after Na+/K+-ATPase blockade by ouabain was studied. RESULTS: It was found that injection of the drug at a dose of 3/4 DL50 leads to changes in heart rhythm variability and motor activity pattern, more pronounced on P16. In the motor activity pattern in 3-day-old rats, there is a tendency to a reduction in the rhythms of the near- and multiminute ranges, while in older rats, on the contrary, their enhancement. The coefficient of variation of motor excitation periods decreased by 12% in 3-day-olds and increased by 35% in 16-day-olds. The decrease in heart rate and respiration is comparable in P3 and P16 rats. Heart rhythm disturbances occur in 37% of 3-day-old and 25% of 16-day-old rats; the arrhythmia rate increases 1,7-2-fold more in animals on P16 than on P3. CONCLUSIONS: The severity of pathological heart rhythm disturbances, including periods of normo/bradycardia, increases with age. Comparison of the character of arrhythmia arising after sodium-potassium pump blockade with pathological heart rhythm observed under conditions of excessive activation of cholinoreactive structures does not allow us to speak about the common mechanisms of their occurrence.