THE COMPARATIVE CHARACTERISTICS OF THE NEUROENDOCRINE RESPONSES OF THE MAGNOCELLULAR AND PARVOCELLULAR VASOPRESSINERGIC NEURONS OF THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS UNDER THE INTERMITTENT HYPOXIC HYPOXIA

Abstract

The brain is the central organ that forms the strategy of neuroendocrine adaptation to various stressors. One of the important mechanisms of brain neuroendocrine adaptation to stress is associated with the paraventricular nuclei of the hypothalamus (PVH). Neuropetides, which are synthesized in PVH, determine the reactivity of all parts of the hypothalamic-pituitary-adrenocortical axis, and ensure the adaptive reactions development and the formation of the body's resistance to stress. Objective.  To study the features of the functional state of vasopressinergic neurons of the paraventricular nucleus of the hypothalamus under influence of many days intermittent hypoxic hypoxia and in the long-term post-hypoxic period. Materials and methods.  The research was carried out on 30 male Wistar rats. Intermittent hypoxia was modeled by a daily 6-hour stay of rats at the stimulated altitude of 6000 m (pO 2  = 9.8%) for 15 days, the post-hypoxic period lasted 10 days. The expression of vasopressin, cFos, HIF-1  , and HIF-3   proteins in PVH subnuclei was investigated by quantitative immunofluorescence methods in serial frontal sections of the hypothalamus. Results.  Intermittent hypoxic hypoxia led to a significant increase in the content of the studied biomarkers of the functional activity of the peptidergic PVH neurons. So, in the lateral part of the posterior magnocellular subdivision of PVH, the vasopressin content was increased by 5.9 times, cFos protein by 80%, HIF-1   protein by 3.4 times and HIF- 3? protein by 3 times. After the end of the hypoxic effects, the vasopressin content in the region of the medial parvocellular subdivision of PVH was increased by 6.6 times, cFos protein - by 37%, HIF-1   protein by 2.5 times, and HIF-3   protein by 73%. In the posthypoxic period, a decrease in the content of vasopressin in PVH was noted. At the same time, while in the lateral part of the posterior magnocellular subdivision of PVH compared with the hypoxic period, the level of vasopressin was decreased by 4 times and remained by 43% higher than in the control animals, in the medial parvocellular subdivision of PVH the neuropeptide content decreased by 11 times and was by 38 % lower than before the onset of the hypoxic effects. Conclusions.  Hypoxic hypoxia stimulates an increase in the formation of vasopressin, proteins of the HIF family and cFos in the lateral part of the posterior magnocellular and medial parvocellular subdivisions of PVH. In the post-hypoxic period, inhibition of vasopressin synthesis in neurons of the medial parvocellular subdivision is observed while maintaining the increased functional activity of neurons in the lateral part of the posterior magnocellular subdivision of the PVH.