In this study we have investigated the mechanisms of adaptive reactions of the organism under the conditions of acute hypoxia exposure in systems with different initial functional state of autonomic regulation. We conducted the record of the cardiointervalogramm of white male rats and the analysis of heart rate variability.

During the introduction of atropine to the control group of rats, we could observe the dose-dependent increase of the index of tension of regulatory systems. This index characterizes the increase of the sympathetic system tone. The resulting changes were verified by stabilization of heart rate and the increased number of isochronous intervals. Effects of propranolol did not result in significant changes of those parameters. During the introduction of atropine in two doses, significant decrease of the statistical parameters was observed. That mainly characterizes the activity of the parasympathetic regulation. The application of propranolol led only to their tendentious increase.

The effect of hypoxia at a "height" of 9000 m developed significant increase of all statistical parameters. The combined effect of atropine and hypoxia caused tendentious decrease of the parameters of heart rate variability. Application of propranolol prior to hypoxia was accompanied by significant dose-dependent increase of all statistical parameters, indicating the activation of parasympathetic regulation. Under the condition of the applying of high dose of propranolol and hypoxia, the character of changes resembled the effect of influence of hypoxia itself at a "height" of 9000 m.

During the application of atropine with the increasing of dose, we observed the reduction of the total spectral power (TP) and varying degrees of the absolute values of all its components. The introduction of propranolol to the control animals at lower dose manifested the increase of TP, within 30 %. However, it was reduced by ~ 46 % with the increase of the medicationdose.

Highly significant increase of TP intensity was registered also under the condition of hypoxia. The changes of the total power were determined by the increase of all components of the spectrum, mostly MF and HF. We could observe the tendency to violation of the vegetative homeostasis, viz. the excessive activation of respiratory component of cardiorhythm and ergotropic energy mobilizing systems.

Application of atropine prior to hypoxia led to decrease of the total power and unidirection of all its components. The exception was for the absolute values of LF under the introduction of large dose of atropine during hypoxia. During the action of atropine in two doses combined with hypoxia, relative values of LF were significantly higher compared with other parameters of spectrum, as well as with similar parameters affected by hypoxia itself. According to the spectral analysis, the introduction of atropine prior to hypoxia leveled hypoxic effect on the activity of the regulatory mechanisms that we studied. Introduction of propranolol prior to hypoxia caused the increase of spectral fluctuations that reached unexpectedly high values with the increase of medication dose, even higher than the effect of hypoxia itself at a "height" of 9000 m. However, with the previous use of a smaller dose of the blocker and hypoxia, those parameters were much lower compared to similar ones affected by hypoxia itself. It is characteristic that the effect of propranolol in its high dose and hypoxia potentiate quite opposite spectral changes, compared to those with the effect of β-blockers. However, it significantly increased the effect of hypoxia at a "height" of 9000 m concerning the activity of the system of cardiac rhythm regulation.

Article Received 08.11.2016

Ключові слова: functional state of autonomic regulation, heart rate variability, hypobaric hypoxia

Повний текст: PDF (Ukr)

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