1. Introduction

In recent years, in professional sports, many scientific researches have been carried out on the changes that occur in the athlete's body during aerobic, mixed, anaerobic stress and their prevention, and significant progress has been made in studying the laws of pathological changes [6,9]. Depending on the level and duration of physical exertion, the central nervous system, hypothalamus-pituitary-adrenal gland, hypothalamus-pituitary-thyroid gland, pituitary-pancreas, hypothalamus-pituitary-gonad systems and the mechanisms of morphological, physiological, pathological changes in the plane of other endocrine glands [2,11]. In the human body, depending on the dynamics of hormones in the athlete's body, cardiovascular system, respiratory system, locomotor system, somatic nervous system and other organs, the mechanisms of the integration of changes, complications, and the prevention of complications are highlighted and developed [3,10].

The main mechanisms of cell damage, compensatory - recovery processes, and genetic mechanisms have been highlighted in professional athletes [6]. In relation to such stresses, the phase and level of development of the mechanism of protective adaptation reaction in the hypothalamo-pituitary and endocrine systems have been studied [4]. The obtained data show that after high-intensity stress, neurohumoral control disorders, development of hidden or obvious endocrine pathologies, changes in hormonal control at one or more stages are possible. Most often, this process is related to the control of the central nervous system, autonomic nervous system, endocrine system, synthesis, accumulation, secretion and transport of hormones, consumption by cells, storage, metabolism, inactivation, it is related to the release of hormones, as well as the disruption of specific tissue receptors [1,7]. The changes that occur in the endocrine system and other systems depending on the levels and duration of physical stress and their interrelation have not been fully studied until now. The analysis of the literature shows that there are few studies on the disruption of the endocrine system in aerobic, mixed, anaerobic stress and depending on the duration of the stress, mainly adenohypophysis, thyroid gland, adrenal gland, gonads, stomach studied in the plane of the pancreas [5,8], however, changes in the recticity of the hypothalamo-pituitary-neurosecretory system depending on the levels and duration of physical exertion were not improved.

2. Research Materials and Methods

The experiment was conducted on 35 white adult rats weighing 160-180 g. In them, the (mixed) physical stress caused by forced chronic swimming in water with a load of 10% of body weight is called using the method of Karkishchenko N.N. Karkishchenko V.N. (2017). Morphofunctional reactivity in the supraoptic nucleus (SOYA) and paraverticular (PVYA), hypothalamo-pituitary tract and neurohepaphysis (NG) was studied in rats during chronic swimming and 1 minute after swimming, 7-21-28-days, 2-3 months. In each group, vital signs: appearance, breathing, swimming activity were monitored [2]. Reactivity of the hypothalamo-pituitary neuroreactive system was assessed by physiological, histological, morphological histochemical, cytophotometric methods. Statistical analysis was performed using the standard package of Microsoft Office programs - Excel 2000.

3. Obtained Data and Its Analysis

The dynamics of the following morphofunctional changes were observed in the reactivity of the animals subjected to mixed stress - i.e., swimming in water with a ratio of 10% to the load.

On the first day of mixed stress compared to aerobic stress in the chronic phase, when animals were observed chronically stressed by water swimming, the rats' swimming in water was active, waterfall, and also short in duration. Supraoptic nucleus in the hypothalamo-pituitary neurosecretory system (SOYA), increased the number of neurosecretory cells with high functional activity in the paraventricular nucleus (PVYA), decreased neurosecretory substances and released more into the blood. In the 3rd month of swimming in the water at a chronic rate of 10% load, the amount of neurosecretory substances (NSM) in the neurohypophysis (NG) was found to be significantly lower than that of aerobic exercise.

When the animals subjected to chronic mixed stress were observed, the swimming of rats was active, splashing, and at the same time, the duration was short, the amount of NSH with high functional activity in the hypothalamo-pituitary neurosecretory system increased in SOYA, PVYA, decreased neurosecretory substances and more than was determined to be released into the blood.

By the 7th day of chronic mixed stress, the rats' swimming in water was active and its duration increased, compared to the aerobic group, there was an increase in the amount of NSH and GLIAL cells with high functional activity in the hypothalamo-pituitary neurosecretory system in the hypothalamo-pituitary neurosecretory system. decrease and excretion into the blood were determined.

By the fourteenth day of the stress, it was observed that the swimming of the rats was regular, strong, and its duration increased. increase in the surface area, and at the same time, an increase in the amount of NSH subjected to karyolysis, a decrease in neurosecretory substances was observed in the NSCs, in the medulla oblongata (OM), hypothalamo-pituitary tract (GGT).

Hypothalamic-pituitary-neurosecretory system reactivity in animals chronically challenged by mixed exercise - i.e., swimming in water at 10% load.

By the 28th day of mixed chronic stress, the water swimming of rats is highly developed, strong, and the duration of free swimming activity is high. In SOYA, as well as in PVYA, the Morphofunctional activity of NSH has the maximum activity, the amount of NSH with high functional activity increases to the maximum, the amount of NSH with medium and low functional activity decreases, the amount of NSH undergoing karyolysis increases, the cell nucleus, the cell cytoplasm decrease in the ratio index, the amount of NSH, the ratio index to the amount of glial cells, the increase in the size of the nucleus of glial cells, the maximum decrease in the amount of neurosecretory substances (NSM) in the NSH, in the middle height (OM), in the neurohypophysis (NG) observed.

In the 2nd month of physical stress, the swimming of rats in water is normal, highly formed, the activity is free, the duration of swimming is high. In SOYA, as well as in PVYA, the Morphofunctional activity of NSH is preserved in the plane of the front group and has maximum activity. It is observed that the amount of NSH with high functional activity is imperceptibly reduced, the amount of NSH with medium and low functional activity is imperceptibly increased, the amount of NSH subjected to karyolysis, the cell nucleus, the ratio of cell cytoplasm to the index increases, the amount of NSH, decrease in the ratio of glial cells, increase in the size of glial cell nucleus, invisible increase in the amount of NSM in NSH, OM, NG was observed.

4. Summary

When rats were subjected to mixed stress by swimming in water at a chronic rate of 10% load, in the 3rd month of provided mixed type of physical stress, the rats' swimming in water was highly formed, their activity was free, and their swimming duration was high. When examining the morphofunctional reactivity in the hypothalamic-pituitary-neurosecretory system, the process of protective adaptation to chronic stress was ensured in SOYA and PVYA. By the 3rd month, the functional activity of SOYA, PVYA NSX remained around the indicators of the 2nd month on the 28th day, increased the amount of karyolysis NSH, cell nucleus, relative to the cell cytoplasm, decreased the amount of NSH, the ratio of glial cells, it was observed that the size of glial cell nuclei increased, the amount of NSM in NSH, OM, and NG increased to an invisible level.

Information about the source of support in the form of grants, equipment, and drugs. The authors did not receive financial support from manufacturers of medicines and medical equipment.

Conflicts of interest: The authors have no conflicts of interest.