CHARACTERISTICS FOR STRUCTURAL CHANGES OF HIPPOCAMPUS OF OLD RATS IN THE SETTING OF COMBINED STRESS AND ITS PHARMACOLOGICAL CORRECTION

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Purpose of the work: the study for structural changes in ventral sections of hippocampus of 24 months old rats in the setting of the combined stresses considering Phenibutum. Material and methods of the study: the investigation was carried out on 30 white outbred male rats ("Rappolovo" Nursery for Laboratory Animal) 24 months old. The stresses were carried out during 7 days within 30 minutes in a special facility, which was represented by the chamber of 28×36×28 cm width, divided into 6 isolated compartments (4×12×28 cm) and allowed combining of several stimuli of different modals (undulating light, loud sound, vibration) every 5 minutes by the stochastic pattern, so that each subsequent effect of stresses was unpredictable to animals. The animals were divided into 3 groups: group 1 consisted of control rats (n=10), group 2 included stressed rats (n=10), group 3 consisted of stressed rats (n=10), which were injected with Phenibutum intragastrically 30 minutes before the stresses at dose 25 mg/kg. Animals of the control group were not exposed to stresses and were given with the physiological solution in accordance with their body weight. Euthanasia was performed using a guillotine method using the “rat guillotine” (AE0702, produced by «Open Science»). Brain was fixed in 10% neutral buffered formalin. The paraffin sections 5 µm thick were stained with hematoxylin and eosin, and thionine by using a Nissl’s method. Photo documentation was done by using the «AxioCam 105 color» camera (Carl Zeiss Microscopy GmbH, Germany). Results: we noted the morphological changes in the area of the front hippocampus CA3. There was a decrease of width and density of the pyramidal layer of neurons compared to the control. In addition, we have discovered the focal areas of neurocytes dropout. During the staining by the Nissl’s a part of pyramidal layer neurons was characterized by various non-specific changes in the form of hyperchromatosis, chromatolysis, and wrinkling. In addition, we determined the damaged neurons in the pyramidal layer, which were characterized by the presence of intense basophilia of perikaryon cytoplasm, in some cases by using a nuclear pyknosis and reducing the size of perikaryon. Complex morphological study of the various sections of the hippocampus of stressed rats treated with Phenibutum did not show any significant differences from the control group, although we observed slightly signified dystrophic changes like bodies wrinkling and cytoplasm hyperchromia of the certain neurons, which we regarded as weakly altered. Conclusions: thus, our findings suggest the expansion of pathological changes and disturbances of cytoarchitectonics of hippocampus in 24 months old male rats as a result of stresses. More signified signs of neuronal affections were observed in CA3 pyramidal layer of the hippocampal area. Animals treated with Phenibutum had a neuronal damage degree lower than in the stressed rats.