Dr. Med., Professor V.N. Ananev¹
Dr. Med., Professor N.Ya. Prokopiev^2
1Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow
²University of Tyumen, Tyumen

Keywords: adaptation to cold, a1-adrenergic receptors, arteries, rabbit, phenylephrine.

Introduction. Winter sports require the body to turn on the adaptive mechanisms of the reaction of the cardiovascular system to the periodic effect of cold. The study [1, 2] showed that severe cold weakened the vasoreactivity of the fingers to direct local cooling. Adaptation to cold leads to activation of the sympathetic part of the autonomic nervous system, which changes the tone of arterial vessels.
The aim of the study was to identify the tone of alpha–1-adrenoreceptors of the arterial vessels of the "shell" of the body (arteries of the musculoskeletal region) and the arterial bed of the "core" of the body (arteries of the small intestine) during a five-day cold adaptation to eight doses of phenylephrine.
Methodology and organization of the study. The study was conducted on two groups of rabbits, control (N1=25) and rabbits (N2=23) after five days of adaptation to cold at (t=- 10'C). The pharmacokinetic and pharmacodynamic properties of a1-adrenoreceptors of the arteries of the body shell and the nucleus of the body in double inverse Linewer-Burke coordinates before and after adaptation to cold were evaluated by the dose-effect reactions on eight doses of phenylephrine.
The results of the study and their discussion. Experiments have shown that after five days of cold adaptation, the blood flow is directed from the "core" of the body to the "shell" of the body, which contributes to warming up and reducing frostbite, but increases the risk of hypothermia. These mechanisms are realized due to an increase in the adaptation to cold in the arteries of the small intestine of active a1-adrenergic receptors (Pm) by 46% on the fifth day. In the arteries of the musculoskeletal region, a1 receptors increased by 13% compared to the control. The sensitivity of (1/K) a1-adrenoreceptors of the arteries was 21% lower than control in the small intestine, and 17% lower than control in the musculoskeletal region.
Conclusions. On the 5th day of adaptation to the cold, the blood flow in the intestine decreased, so athletes can be recommended a lighter diet, eating more often, but in small doses. Since the blood flow from the intestine is more directed to the musculoskeletal area, the warming of the external tissues of the body improves, the survival of the body improves on the fifth day of cold adaptation. But with extreme cold, prolonged exposure to the cold, these mechanisms lead to rapid heat loss and frostbite. Our research shows that five-day adaptation to the cold does not provide sufficient safety and requires special attention to the training regime of athletes in the cold.

References

1. Keramidas M.E., Kölegård R., Gäng P., Wilkins F., Elia A., Eiken O. Acral skin vasoreactivity and thermosensitivity to hand cooling following 5 days of intermittent whole body cold exposure.Am.J.Physiol.Regul.Integr.Comp.Physiol.2022.Jul.1;323(1):R1-R15.doi: 10.1152/ajpregu.00021.2022.
2. Nikolaidis P.T., Veniamakis E., Rosemann T., Knechtle B. Nutrition in Ultra-Endurance: State of the Art. Nutrients. 2018 Dec 16;10(12): doi: 10.3390/nu10121995.