Dynamics of histological changes in histaminergic neurons of the rat hypothalamus in postnatal ontogenesis

Abstract

Histaminergic neurons in adult vertebrate brain are confined to the posterior hypothalamic area, where they are comprised of scattered groups of neurons referred to as the tuberomammillary nucleus. Histamine regulates hormonal functions, sleep, food intake, thermoregulation and locomotor activity. Histaminergic neurons in adult animals under normal conditions and in some pathological conditions are described. However, a study of these neurons development in the postnatal ontogenesis dynamics has not been conducted. The morphofunctional state of histaminergic neurons of the hypothalamic E2 nucleus in the postnatal ontogenesis dynamics was assessed. The study was performed on the offspring of outbred white rats (45 animals). The decapitation of animals was carried out on the 5, 10, 20, 45 and 90th days after birth. We used histological, histochemical, morphometric and statistical research methods. The data obtained were processed by nonparametric statistics methods. From the 5th to the 90th day of rat postnatal ontogenesis, there is a significant increase in the size of the histaminergic neurons pericarions of the hypothalamic E2 nucleus (especially from the 5th to the 10th day). It is accompanied by a decrease in the bodies location density of the studied cells and an increase in the distance between them (especially from the 5th to the 20th day), which indicates a neuropil intensive growth. Over the indicated period of postnatal development, a significant decrease in the hyperchromic neurons number is observed, which correspond to a decrease in the ribonucleoproteins amount in the cytoplasm of the described neurocytes. Development of brain histaminergic neurons from the 5th to the 90th day of rat postnatal ontogenesis is characterized by an intensive growth of their pericaryons, a decrease in their location density and stabilization of the morphofunctional state of the studied neurocytes.