Change in the State of Neurons in the Medulla Oblongata of Fish Perccottus glehni during Wintering (Ultrastructural and Biochemical Studies)

摘要

The aim of this study was to conduct a comparative analysis of the ultrastructure of neurons of the medulla oblongata (MO) in fish during wintering and to identify the role of components of the synthesis and degradation systems in adapting to unfavorable conditions (hypoxia, hypothermia, starvation). Mautner neurons (MNs) localized in the MO have a wide set of metabolic and functional capabilities. They were shown to be able to accumulate glycogen, having their own system of glycogenesis, glycogenolysis, and deposition of glycogen, which is an alternative source of energy during wintering. The study of MO neurons located near the somatic part of the MN showed that some of these cells, like the MNs, are able to induce a similar additional energy source—glycogen—as indicated by the appearance of glycogen fields in their cytoplasm during wintering. In such cells, as in MNs, during this period, the components of the ultrastructure remain in an active state. The rough endoplasmic reticulum and polyribosomes retain an intact structure in them. At the same time, the Golgi apparatus is reorganized significantly and the catabolic system is activated. In other cells adjacent to MNs, in which there is no accumulation of glycogen, structural degradation is observed. Thus, the features of the ultrastructure of the studied MO neurons indicate the important role of glycogen in their functioning during the wintering period. It can be suggested that, in the medulla oblongata, MNs and some other neurons retain their activity, forming specific centers that are involved in the adaptation of fish to adverse wintering conditions.