Discovering the mechanisms underlying homeostatic regulation in brain neural network formation and stability processes is one of the most urgent tasks in modern neuroscience. Brain-derived neurotrophic factor (BDNF) and the tropomyosin-related kinase B (TrkB) receptor system have long been considered the main regulators of neuronal survival and differentiation. The elucidation of methods for studying neural network activity makes investigating the complex mechanisms underlying neural network structure reorganization during development and detecting new mechanisms for neuronal activity remodeling possible. In this in vitro study, we investigated the effects of chronic BDNF (the main TrkB stimulator) and ANA-12 (a TrkB receptor system blocker) administration on the formation of neural-glial networks. The formation of spontaneous bioelectrical activity and functional neural structure depend on TrkB receptors, and blocking TrkB receptors inhibits full bioelectrical activity development. Cross-correlation analysis demonstrated the decisive role of TrkB in the formation and “strengths” of activity centers. Even though an appropriate ANA-12 concentration is non-toxic to nerve cells, numerous cells in culture medium containing this reagent do not exhibit metabolic activity and are not functionally involved in signal transmission processes. Electron microscopy studies revealed that chronically influencing the TrkB receptor system significantly alters synaptic and mitochondrial apparatus capture in cells, and functional analysis of mitochondrial activity confirmed these findings. Because knowledge of interactions between TrkB-mediated regulation and the mitochondrial state under normal conditions is rather limited, data on these relationships are particularly interesting and require further investigation. Thus, we assume that the molecular cascades mediated by TrkB actively participate in the formation of functionally complete brain neural networks.

Brain-derived neurotrophic factor (BDNF) is one of the key signaling molecules that supports the viability of neural cells in various brain pathologies, and can be considered a potential therapeutic agent. However, several methodological difficulties, such as overcoming the blood–brain barrier and the short half-life period, challenge the potential use of BDNF in clinical practice. Gene therapy could overcome these limitations. Investigating the influence of viral vectors on the neural network level is of particular interest because viral overexpression affects different aspects of cell metabolism and interactions between neurons. The present work aimed to investigate the influence of the adeno-associated virus (AAV)-Syn-BDNF-EGFP virus construct on neural network activity parameters in an acute hypobaric hypoxia model in vitro. Materials and methods. An adeno-associated virus vector carrying the BDNF gene was constructed using the following plasmids: AAV-Syn-EGFP, pDP5, DJvector, and pHelper. The developed virus vector was then tested on primary hippocampal cultures obtained from C57BL/6 mouse embryos (E18). Acute hypobaric hypoxia was induced on day 21 in vitro. Spontaneous bioelectrical and calcium activity of neural networks in primary cultures and viability tests were analysed during normoxia and during the posthypoxic period. Results. BDNF overexpression by AAV-Syn-BDNF-EGFP does not affect cell viability or the main parameters of spontaneous bioelectrical activity in normoxia. Application of the developed virus construct partially eliminates the negative hypoxic consequences by preserving cell viability and maintaining spontaneous bioelectrical activity in the cultures. Moreover, the internal functional structure, including the activation pattern of network bursts, the number of hubs, and the number of connections within network elements, is also partially preserved. BDNF overexpression prevents a decrease in the number of cells exhibiting calcium activity and maintains the frequency of calcium oscillations. Conclusion. This study revealed the pronounced antihypoxic and neuroprotective effects of AAV-Syn-BDNF-EGFP virus transduction in an acute normobaric hypoxia model.

The aim of the study was to study the effect of TrkB-mediated action of the brain-derived neurotrophic factor (BDNF) on animal survival and mitochondrial respiratory chain activity in acute hypobaric hypoxia model in vivo. Materials and Methods. In vivo experiments were performed on mature male CBA mice weighing 20-25 g. In order to modulate acute hypobaric hypoxia, the animals were placed in the hypobaric chamber (220-240 mm Hg) which simulates conditions corresponding to the altitude of 10 000 m above sea level. The oxygen consumption rate by the brain mitochondria under the hypoxic influence was evaluated using a high-resolution OROBOROS Oxygraph-2k respirometer (OROBOROS Instruments, Austria). Results. Preventive BDNF application has been established to increase the survival of the CBA-line animals after acute hypobaric hypoxia modeling and to influence favorably the work of mitochondrial respiratory chain complex I. Conclusion. BDNF increases animal resistance to acute hypobaric hypoxia and influences the work of mitochondrial respiratory chain through TrkB-signaling mechanisms. Antihypoxic effect of BDNF is realized by maintaining the activity of NADH-dependent pathway of substrate oxidation and ATP synthesis.

The aim of the investigation was to study the effect of chronic and acute prenatal hypoxia on the parameters of CNS functional activity and to assess the role of mitochondria in the protection of the CNS against experimental hypoxic influence in vivo. Materials and Methods. The experiments in vivo were performed on C57BL/6 mice. In order to model chronic prenatal hypoxia, pregnant female mice were placed daily into a hypobaric chamber beginning with the fourteenth day of gestation up to delivery. 280-300 mm Hg pressure corresponding to the altitude of 8000 m above sea level was maintained in the chamber for 2 h. Acute prenatal hypoxia was modeled on the eighteenth day of gestation. Pregnant females were placed for 4-5 min (till the first agonal breath) in the hypobaric chamber under 220-240 mm Hg pressure corresponding to the altitude of 10,000 m above sea level. Oxygen consumption rate by mice brain mitochondria was assessed on the first day of the post-natal period using a high-resolution Oxygraph-2k respirometer (Oroboros Instruments, Austria). To determine a general state of the CNS in the remote post-hypoxic period, a neurological status of the 4-week-old animals was evaluated according to the neurological deficit scale for small laboratory animals and Garcia's scale. Mnestic and cognitive abilities were also tested in Morris water maze. Results. Protocols of acute and chronic prenatal hypoxia modeling for mice have been designed. Acute hypoxic damage has been shown to result in the significant decrease of the basal oxygen consumption rate and intensity of oxidative phosphorylation by the brain

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