To identify the primary ultrastructural changes in the CA1 region of the rat`s hippocampus after a single exposure to an air blast wave.

Materials and methods. The study was conducted on healthy 12 sexually mature male Wistar rats weighing 220-270 g, kept under standard conditions in the vivarium of Dnipro State Medical University. The animals were randomly divided into two groups: experimental (n = 6) and sham (n = 6). The rats of experimental group were exposed to an air blast wave with a pressure of 30.1 ± 2.9 kPa. One hour after exposure to the blast wave, animals in both groups were anaesthetised with halothane and euthanised, followed by craniotomy, removal of the hippocampus and conducted electron microscopic examination using standard procedures. All manipulations were carried out in accordance with the rules of current legislation on bioethical treatment of experimental animals.

Results. It was established that a single exposure to a blast wave with a pressure of 30.1 ± 2.9 kPa resulted in mild trauma, as indicated by the absence of cell membrane rupture with cytoplasm and organelles escaping into the extracellular space and the absence of complete vessel rupture with massive haemorrhages. Signs of primary neuronal injury included increased nuclear membrane permeability and nuclear chromatin rarefaction, significant perinuclear oedema, cytoplasmic vacuolisation, and extracellular oedema. Damage to the blood-brain barrier vessels was detected in the form of perivascular oedema, thickening and delamination of the vessel membrane due to its oedema, and cavitation bubbles were present in the vascular lumen. Nerve fibres were also traumatized, as indicated by myelin delamination.

Conclusions. It has been established that swelling of neurons and increased permeability of the nucleus membrane and its oedema, as well as delamination of myelin fibres (a decrease in the sphericity coefficients of axonal profiles by 11 % (p < 0.05) and dendritic profiles by 33 % (p < 0.01) in the hippocampus of experimental rats). Signs of primary injury due to the impact of the blast wave were found on the side of the blood-brain barrier in the form of perivascular oedema, thickening and delamination of the vascular membrane due to its oedema (47 % increase in the relative area of electron-transparent sections (p < 0.01) of the hippocampus of experimental rats). The presence of a cavitation bubble in the hippocampus vessel indicates the persistence of the initial damage due to its ability to cause hydraulic shocks.