Introduction. The individual development of every living organism starting from the zygote formation to natural death is subject to age-related changes. In its turn, a certain age period in the ontogenesis of an organism is characterized by the corresponding features peculiar to it, which gradually develop in all physiological systems (respiratory, digestive, excretory, sensory, etc.), causing a decrease in functional activity of the organism. The most sensitive and vulnerable are those systems that ensure the metabolism at the cellular level, namely transport (blood and lymphatic) and regulatory (endocrine, nervous, immune) systems. The cardiovascular system with its multilevel regulation provides the necessary level of functioning of the whole organism. Vegetative support of the cardiovascular system can be carried out by means of central, humoral and segmental mechanisms of regulation. It should be noted that one of the most promising and frequently used methods used to determine the functional state of autonomic regulation of the cardiovascular system is heart rate variability (HRV). HRV indicators not only characterize the state of the cardiovascular system and the mechanisms of its regulation, but are also a highly informative indicator of the regulatory activity of all departments of the autonomic nervous system. Purpose. Modulation of ontogenetic features of autonomic regulation of the cardiovascular system of male rats by indicators of heart rate variability. Materials and methods. We have conducted the studies of the modulation of ontogenetic peculiarities of autonomic regulation of the cardiovascular system of males rats by parameters of heart rate variability. Rats were divided into five age groups under the age classification of laboratory animals of Zapadnjuk I. P. An electrocardiogram (ECG) was recorded in rats by means of needle electrodes (2nd standard lead). Indicators of the heart rate variability (HRV) analysis were evaluated according to Baevsky R.M. Results. In juvenile, young, and mature male rats, there was a significant increase in heart rate and Mo decrease, a tendency to AMo increase, no probable changes in index of autonomic equilibrium (IAE), and a likely increase in VAR (only in males) and stress index (SI) (only in young males), which testifies to the advantages of the rapid (reflex) heart rate regulation system due to the sympathetic disorder of the autonomic nervous system (ANS) and enhancement of the activation of the humoral level of regulation. Conclusions. The high level of sympathetic effects in heart rate modulation in young and mature males is a reflection of the development of balanced autonomic regulation. According to the study results, presenile and senile males have a predominance of parasympathetic effects on the heart rate regulation, which may be associated with both its activation and the inhibitory activity of the sympathetic link in the cardiovascular system regulation. Thus, in male rats during the period of pronounced aging changes there is an increased manifestation of adaptive- compensatory reactions of the organism. The high level of sympathetic influences in the modulation of heart rate of young and mature males is a reflection of the developed balanced autonomic regulation. According to research, in males of presenile and senile age, the predominance of parasympathetic effects on the regulation of heart rate, which may be associated with both its activation and inhibitory activity of the sympathetic link in the regulation of the cardiovascular system, due to which there is increased manifestation of adaptive-compensatory reactions of the organism.
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