[State of autonomic regulation of heart rhythm in young and aged rats before and after application of different regimens of rhythmic extreme cooling.].

The influence of various rhythmic extreme cold effects on the state of autonomic regulation of heart rate in young and aged rats was studied. According to the spectral analysis of heart rate variability, it has been found that in young rats, using rhythmic extreme cold exposures (RECE) temperature regimens of (-120 °С; -120 °С; -120 °С) and (-60 °С; -120 °С; -120 °С) significantly increased adaptive capabilities of the body due to the activation of its own homeostatic regulatory systems. At the same time, the combined regimen of RECE (-60 °С; 120 °С; -120 °С) occurred to be the most optimal for aged animals, since its use was not accompanied with an excessive activation of sympathoadrenal system at the early stages of experimental studies, in contrast to the regimen (120 °С; -120 °С; -120 °С). In addition, the use of this cooling mode contributed to a statistically significant increase in the total power of spectrum of neurohumoral regulation not so much due to a rise in activity of humoral-metabolic regulation link, the prevalence of which is characteristic of an old age, but due to an increase in the tone of vegetative centers, herewith the parasympathetic effects on the myocardium prevailed sympathetic ons.