Effect of melatonin on heart rate variability in rats with adrenaline-induced myocardial dystrophy

Abstract

The pineal hormone melatonin actively regulates the body’s adaptive reactions to changes in external environmental conditions and internal homeostasis. Melatonin, as a pharmacological agent with antioxidant properties, is widely used to correct disorders resulting from oxidative stress. The present study aimed to investigate changes in cardiac activity under the influence of this hormone, in particular, the effect of melatonin on heart rate variability in laboratory rats with a model of adrenaline-induced myocardial dystrophy. The degree of regulatory tension and neural control mechanisms and mechanisms of nervous regulation was assessed by mathematical analysis of heart rate variability, which is one of the integrative methods for evaluating the functional activity of the body’s regulatory systems. The main results of the study demonstrated that autonomic regulation of the heart showed an increase in the vegetative balance index (VBI), alongside a decrease in heart rate frequency (HRF) and tension index (TI), indicating reduced sympathetic-adrenal stimulation of the heart under conditions of adrenaline-induced myocardial dystrophy. During the 10 day administration of melatonin to rats with adrenaline-induced myocardial dystrophy, an increase in autonomic activity was observed, with an emphasis on heightened parasympathetic nervous system influence on the heart, which contributed to a lower risk of arrhythmias and myocardial infarction. In particular, changes in heart rate were accompanied by HRF fluctuations ranging from 339 to 451 beats/min and an increase in TI from 1,279 to 7,942 units. Twenty-four hours post-adrenaline administration, TI and HRF decreased by 22% and 6.5%, respectively. In rats with pineal hyperfunction, the mean HRF was 414 ± 26 beats/min, TI increased by 27%, and the mean VBI increased by 14%. The observed effects of melatonin indicate that it is a potentially useful tool for preventing adrenaline-induced myocardial damage. The results of the study offer new possibilities for correcting the functional state of the heart and enhancing understanding of the mechanisms through which different levels of pineal gland activity influence cardiac function.