Repeated blast-induced neurotrauma: histopathological changes in the hippocampus and cerebellum of rats

Repeated blast-induced neurotrauma impairs the quality of life of military personnel and civilians who have suffered from repeated blast wave exposure. The aim was to study histopathological changes in the hippocampus and cerebellum of rats after repeated 3-fold blast wave exposure. The study was conducted on 40 male rats, randomly divided into control (n=5) and experimental groups (n=35). The experimental group of rats was divided into 5 animals for each observation period: 30 minutes, 1st, 3rd, 7th, 14th, 21st and 28th days, to track the dynamics of morphological changes. Animals of the experimental group were anesthetized with halothane and fixed on the abdomen so that the muzzle was at a distance of 5 cm from the device outlet. They were exposed to an excess pressure of 31.6±4.8 kPa. Then the animals were decapitated, the brain was removed, the hippocampus and cerebellum were separated, fixed and stained with hematoxylin-eosin according to the standard method. Light microscopy of the hippocampus demonstrated signs of karyopyknosis already 30 minutes after 3-fold exposure to the blast wave, as well as signs of perivascular and pericellular edema, and hypochromia of pyramidal cells. These signs intensified during all subsequent periods of observation. Light microscopy of the cerebellum demonstrated signs of pericellular edema in the Purkinje layer area 30 minutes after repeated exposure to the blast wave, which increased on the 1st and 3rd days, and then began to decrease. Hypochromia of Purkinje cells was observed throughout the entire period of observation of the experimental animals. On the 7th, 21st and 28th days, clearly visible signs of engorgement of the cerebellar blood vessels were observed. Thus, our morphological study showed that after 30 minutes, on the 1st, 3rd, 7th, 14th, 21st and 28th day after repeated exposure to a blast wave, primary and secondary brain changes were observed. In the hippocampus, signs of karyopyknosis and chromatolysis of pyramidal cells, as well as perivascular and pericellular edema were observed. In the cerebellum, hypochromia of Purkinje cells, pericellular edema in the Purkinje layer zone and hyperemia of blood vessels were detected. These changes can serve as biomarkers of traumatic disorders after 3-fold exposure to a blast wave.