Expression of the P53 Protein and Morphological Changes in Neurons in the Pyramidal Layer of the Hippocampus After Simulation of Surgical Interventions in the Nasal Cavity in Rats

Background/Aims: to determine the role of surgical stress on the formation of p53-positive and dark neurons (DN) in the hippocampus, and to examine the parallelism of their formation in the pyramidal layer of the hippocampus. Methods: Simulated septoplasty was performed on 20 Wistar rats. The hippocampus and dentate gyrus (DG) were examined, in which the number of DN and p53-positive neurons was determined at 2, 4 and 6 days after surgery. In each rat, 10 brain slices were stained with antibodies to p53 protein with Meyer's haematoxylin and 10 slices were stained with Nissl toluidine blue. Hippocampal subfields CA1, CA2, CA3 and DG were studied. In the pyramidal subfield layer, the absolute number of neurons that were nuclear antibody-positive to p53 protein was counted, as well as the number of dark neurons. The counting area in each subfield was 20934±1260 µm2. Neurons are counted using the Aperio ImageScope program. For the histological specimen analysis, the ImageJ software was used. The data obtained using cell counting methods were presented as mean ± SE. Then, they were compared between both groups using a t-test SPSS 21software. Results: Compared with the control group (n = 5), the number of DN and p53-positive neurons increased in experimental animals at all periods. A direct relationship was obtained between the increase in the number of DN and p53-positive neurons in the hippocampal formation. Septoplasty simulation in rats results in the pathogenetic cascades onset, which, in its turn, changes the morpho-functional properties of neurons of the pyramidal layer of the hippocampus and contributes to their neuroplasticity. Activation of NMDS receptors of neurons during stress apparently, initiates two ways of neuron life – the beginning of p53 protein expression and the DN formation. Both ways can finally lead to apoptosis. Conclusion: The formation of dark neurons and the expression of the p53 protein in them are most likely to be interconnected and can probably provide neuroprotective mechanisms.