Fedorіak I. V., Bulyk R. Ye., Smetanіuk O. V.

MELATONIN EFFECTS ON THE STATE OF NEURONS IN THE HYPOTHALAMUS PARAVENTRICULAR NUCLEI OF RATS UNDER CONSTANT ILLUMINATION

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Fedorіak I. V., Bulyk R. Ye., Smetanіuk O. V.

Heading:

MORPHOLOGY

Type of article:

Scientific article

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One of the key links in the formation of the brain's neuroendocrine adaptation to stress is the hypothalamic paraventricular nuclei, which determine the reactivity of all parts of the hypothalamic-pituitary-adrenocortical system and ensure the development of adaptive responses to the formation of the body's resistance to stress factors, in particular prolonged illumination. In view of this, it is important to determine the effects of melatonin on the morphodensitometric parameters of the medial parvocellular subnuclei of the rat’s hypothalamic paraventricular nuclei under light stress. The study was performed on 36 male outbred white rats aged 24-27 months, divided into 3 groups. Quantitative parameters of the area of neurons, their nuclei and nucleoli, and RNA content in the cytoplasm of cells, their nuclei and nucleoli were obtained in a semi-automatic mode using licensed software. Based on the studies, it was found that the morphodensitometric parameters of the medial parvocellular subnuclei of the rat’s hypothalamic paraventricular nuclei at 14:00 were significantly higher than during the night observation period (2:00). The administration of melatonin against the background of constant illumination did not significantly change the dynamics of the activity of the studied structures, which remained higher during the daytime observation period and was similar to that of animals under the conditions of 12.00L:12.00D and 24.00L:00D. This picture can be argued by the fact that stressful exposure during the light period of the day is accompanied by an increase in the level of melatonin in the blood. This provides a corrective suppression of the hypothalamic-pituitary-adrenocortical system in order to bring the hormonal status in line with the strength of the stressor effect and is considered one of the factors of the stress-limiting mechanism activated in response to the mobilization of the stress-realizing system.

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Publication of the article:

«Bulletin of problems biology and medicine», 2025 Issue 3,178, 432-442 pages, index UDC 612.826.4:612.017.2

DOI:

10.29254/2077-4214-2025-3-178-432-442