CORTISOL LEVEL AND DYNAMICS OF BEHAVIORAL REACTIONS IN MICE UNDER THE INFLUENCE OF INTERLEUKIN-2 DURING PHYSICAL TRAINING

Abstract

Summary. The reaction of the hypothalamic-pituitary-adrenal system, accompanied by an increase in blood cortisol, adequate to the amount of exercise, can serve as an important early indicator of overtraining and stress. Stress, in turn, leads to significant changes in the central nervous system, which is clearly manifested in behavioral reactions. Interleukin-2 (IL-2) may have a simultaneous effect on the regulation of homeostasis in the brain and immune system. The drug IL-2 is effectively used in the treatment of immunosuppression caused by stress, and has stimulating and antidepressant effects.

The aim of the study – to evaluate the effect of IL-2 on cortisol levels and the dynamics of behavioral responses in mice under physical stress.

Materials and Methods. The study was performed on adult male laboratory mice. Five experimental and one control (without physical training) groups of animals were formed. Group I received an inhibitor of IL-2 (Cyclosporine) (10 mg/kg), groups II, III and IV – IL-2 (Roncoleukin) in concentrations of 5000, 7500 and 30,000 IU/kg, respectively, group V – sterile saline. The method of forced swimming to complete exhaustion with a load was used as physical training. The content of cortisol in the blood serum was determined using reagents "Cortisol – ELISA". The behavior of animals was studied using the method of “Open field”.

Results. Stimulation of IL-2 in high concentrations led to a significant increase in serum cortisol levels in mice at 4 and 6 weeks compared to the control and previous period (p≤0.05). Animals administered IL-2 at medium concentrations had a moderate increase in cortisol levels, which increased during all phases of adaptation to exercise. Significant differences were observed compared with the control (respectively, by 51.8 % – at the 4th, by 36.5 % – at the 6th week, p≤0.05). In the group of animals with IL-2 inhibition, cortisol levels at week 4 decreased compared to the previous period (by 16 %, p≤0.05) with a subsequent significant increase (by 110 %, p≤0.05). Groups of animals with low-concentration IL-2 stimulation and no drug exposure showed an increase in cortisol levels compared to controls at week 4 and compared to previous values at week 6 of exercise. During all periods of the experiment, there was a difference in behavioral activity in the “Open field” test depending on the period and the effect of IL-2 of different concentrations or its inhibition.

Conclusions. It was found that the introduction of IL-2 affects the concentration of cortisol in the serum of laboratory mice that were exposed to exercise. Animals administered IL-2 at medium concentrations did not have a significant increase in cortisol levels. At low concentrations of IL-2, cortisol levels increased with a significant decrease in the recovery phase. Under conditions of high concentrations of IL-2, cortisol levels increased during all weeks, with a significant jump in the last week of exercise. Therefore, average concentrations of IL-2 have a stress-protective effect under exercise. In a model of physical stress in white mice, it was shown that the introduction of IL-2 affects the behavior of experimental animals. At medium concentrations, IL-2 leads to a decrease in anxiety, increased motor activity of animals and increased research behavior.