Features of the Effects of Serotonin and Dopamine on Changes in Heart Rate Variability in Non-Linear Rats under Conditions of Acute Stress

Changes in indicators of heart rate variability after a single injection of serotonin (200 μg/kg) or dopamine (60 μg/kg) were analyzed in male non-linear rats at rest and during acute stress. At rest, administration of serotonin is accompanied by an increase in the role of the vasomotor center in the formation of heart rate variability; administration of dopamine causes a moderate weakening of HF waves. In both cases, no sharp shifts in the sympathetic–parasympathetic relations are seen, but a more variable rhythm is formed under the effect of serotonin. Under conditions of acute stress, the increase in HR after injection of serotonin is half as much as in the control series, a trend towards weakening of the power of VLF- and even LF-waves is observed. After dopamine injection, a sharp increase in HR and strain index and a decrease in the power of waves of all spectral ranges and the centralization index are observed at the beginning of stress, but by the 30th min, tachycardia becomes moderate, the powers of all waves are restored; HF waves dominate in the spectrum, but potentiation of VLF- and LF-waves and growth of the centralization index are not observed in contrast to the control series. In general, serotonin and dopamine exhibit stress-limiting properties and moderate activation of sympathoadrenal influences and the suprasegmental level of regulation under stress conditions, but after dopamine injection we observed increased reactivity at the beginning of stress and less variable HR. Therefore, serotonin has more pronounced stress limiting effects, which can be revealed by heart rate variability analysis.