The effect of hydrogen sulfide donor NaHS at a dose of 7.4 mg/kg on rats’ heart rate variability (HRV) in 30 minutes, 3 hours, 1 and 2 days after introduction was investigated. All experiments were performed in accordance with applicable requirements for humane attitude to animals (Strasbourg, 1986). Activity of different parts of regulatory systems was evaluated based on spectral, statistical methods and variation pulsometry of HRV. Photoplethysmogram transducer for 5-minute recording of peripheral pulse and assessing HRV were used.

Results of the studies established that the total spectrum power statistically significantly increased (on 78 %, p < 0,05) according to initial level due to increased spectral power in all frequency bands in 30 minutes after entering H2S donor. In the internal structure of spectrum was increased part of HF. The increase in spectral power in the range of high-frequency oscillations correlates with increased part of CV (on 75 %, p < 0,05), other statistical indicators, as well as growth of MxDMn (on 53 %), which generally indicates activation of autonomic contour of cardiac activity regulation. Reported also reduction of AMo (on 18 %) and sympathovagal index (MF/HF) according to initial level. set of changes in HRV indicates mobilizing all parts of regulatory systems with the prevailing activation of the parasympathetic nervous system (PSNS) in the 30th minute after introduction of NaHS was discovered.

Recovery to near baseline values of TP was observed in the 3rd hour of study. Increasing of the part of MF to the original values and exceeding of LF part on 12 % compared to the initial level and 18 % to the previous level was reported. Growth of MF/HF ratio and reduced heart rate almost to original values was established. The normalization of HRV parameters after 3 hours after introduction of NaHS allows us to consider the change in the previous study period (30 minutes) as the quick mobilization of functional reserves at all levels of regulatory systems.

On the 1st day after the introduction of H2S donor was established increasing of TP according to the initial level (by 36 %, p < 0,05) and levels in the 3rd hour, but less pronounced compared to the 30th minute after introduction of NaHS. In the largest extent, spectral power increased in the range of high-frequency oscillations. In addition, upward trend of balanced autonomous components (HF + MF), reduced of MF/HF ratio, which was prognosticaly favorable sign of regulatory systems status were observed. There was also an increase of statistical parameters as MxDMn regarding to initial values and in the 3rd hour but less severily compared to the 30th minute. Enabling of regulatory influences maintained the heart rate at baseline. In the 2nd day after introduction of NaHS decreasing of TP according to the 1st day was set, which, however, was 12 % higher than the initial level. Normalization of AMo, statistical indicators were also marked, but MxDMn still stay increased on 35 % to the initial values.

Thus, exogenous stimulation of paracrine H2S-dependent signaling processes by introduction of NaHS significantly affect systemic regulatory mechanisms at different levels. Changes of HRV parameters, that indicate activation of various parts of regulatory systems with overwhelming mobilization of PSNS in the 30th minute after introduction of NaHS, have a phase character and can be regarded as prognosticaly favorable effect of this dose (7.4 mg/kg) of administered substance.

Keywords: gaseous transmitter, hydrogen sulfide, heart rate variability, experimental animals

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