EFFECTS OF MELATONIN ON MELATONIN RECEPTOR DENSITY IN THE SUPRACHIASMATIC NUCLEUS OF RAT HYPOTHALAMUS UNDER STRESS CONDITIONS

Bulyk R. E., Bulyk T. S., Smetanyuk O. V., Vlasova K. V., Kryvchanska M. I.

MORPHOLOGY

Scentific article

Abstract. Introduction. In mammals, the epiphyseal hormone melatonin plays a key role in the regulation of cyclic physiological processes. Its receptors and binding sites are involved in cellular response. Limitation of motor activity (hypokinesia or immobilization) is a powerful stressor factor that causes desynchronosis. The aim is to elucidate the effect of immobilization stress on melatonin type 1A receptor density in rat hypothalamic suprachiasmatic nucleus neurons and the effects of exogenous melatonin. Materials and methods. Experiments were performed on nonlinear male white rats weighing 200-220 g. Immobilization stress was simulated by keeping rats in plastic penal cages for 6 hours daily for 7 consecutive days. Melatonin (Sigma, USA) was administered by peritoneal injection for 7 days against the background of immobilization stress. Animals were divided into 3 series, in each of which biomaterial was collected at 2 p.m. and at 2 a.m. using immunohistochemical, densitometric and statistical methods of investigation. Results. In animals under long immobilization, the optical density of specific staining of the studied structures was significantly lower than that of the control series. Melatonin injections under immobilization stress caused the index increase in rat hypothalamic SN neurons especially at 2 a.m. in comparison with animals kept under long immobilization without drug administration. Conclusions. The melatonin type 1A receptor density in neurons of the suprachiasmatic nucleus of the hypothalamus has a clear circadian rhythm, with the highest values at 2 a.m., whereas at 2 p.m. it decreases. In animals subjected to immobilization stress, the optical density of specific staining for melatonin type 1A receptors was significantly lower than in controls. Injection of melatonin caused significant increase in mean values of melatonin receptor density to melatonin type 1A in SN neurons of animals’ hypothalamus.

suprachiasmatic nucleus, immobilization stress, melatonin.

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«Bulletin of problems biology and medicine» Issue 3 (161), 2021 year, 245-248 pages, index UDK 591.185.6

10.29254/2077-4214-2021-3-161-245-248