The aim. To expand current understanding of the expression characteristics of p53 and Annexin A5, as well as the nature of their correlations in the basal magnocellular nucleus (BMN) of rats undergoing colchicine-induced neurodegeneration.

Materials and methods. This study was conducted on 30 male Wistar rats. Neurodegeneration was induced in the group of animals (n = 10) via intracerebroventricular administration of colchicine. The comparison groups included intact rats (n = 10) and sham-operated rats (n = 10), the latter receiving an intracerebroventricular injection of 0.9 % NaCl instead of colchicine. Subsequently, the animals were euthanized with sodium thiopental, and their brains were collected for immunofluorescent analysis of p53 and Annexin A5 expression. The data obtained were analyzed statistically.

Results. The intensity of p53-positive cell fluorescence within the studied brain structure did not significantly differ between experimental groups. In contrast, the corrected total cell fluorescence of Annexin A5-positive cells in the BMN was significantly higher in colchicine-treated rats – by 24.2 % and 46.9 % – compared to intact and sham-operated animals, respectively. Evaluation of the colocalization degree between p53 and Annexin A5 immunoreactive materials with the nuclear stain DAPI in BMN cells demonstrated a low level of colocalization for both markers. However, compared to the neurodegeneration group, the intact and sham-operated animals showed statistically significant differences in this parameter for both p53-positive and Annexin A5-positive cells. Assessing the number of immunopositive cells, colchicine administration resulted in nearly a threefold increase in p53+ cells compared to intact animals and an approximately two-and-a-half-fold increase compared to sham-operated animals. Regarding Annexin A5+ cells, their number nearly doubled compared to both comparison groups. Colchicine treatment also led to a nearly threefold increase in p53+ cells and a twofold increase in Annexin A5+ cells compared to controls.

Conclusions. In the basal magnocellular nucleus of rats subjected to intracerebroventricular colchicine administration, a statistically significant increase in corrected total cell fluorescence values for Annexin A5-positive cells – but not for p53-positive cells – was observed compared to intact and sham-operated animals. Additionally, there was a significant increase in the number of both p53-positive and Annexin A5-positive neurons. Moreover, p53-positive cells in the BMN of colchicine-treated rats exhibited a higher degree of colocalization with DAPI compared to the comparison groups. Importantly, no correlation was found between the fluorescence intensity of Annexin A5-positive cells and the degree of DAPI colocalization with p53 in the neurons of the BMN under conditions of colchicine-induced neurodegeneration.