Structural and functional changes in neocortical neurons of white rats following a 20-minute occlusion of common carotid arteries

Abstract

Aim. To study sensorimotor cortical neurons of white rats in the control conditions and after a 20-minute occlusion of common carotid arteries. Methods. Neuronal cytoarchitectonics of rat sensorimotor cortex (SMC) was studied in the control conditions (n = 5) and at 1, 3, 7, 14, 21, and 30 days (n = 30) following a 20-minute occlusion of common carotid arteries using light (hematoxylin and eosin; Nissl staining), fluorescent (DAPI staining), immunofluorescence (neuron-specific enolase, NSE), and electron microscopy. All morphotypes of modified pyramidal neurons were described in detail for the SMC of albino rats after acute ischemia according to recommendations of the Nomenclature Committee on Cell Death (2009). The morphometric analysis was performed using the ImageJ 1.46 software. Results. Using a set of morphometric methods allowed to classify neurons and demonstrate a possibility of apoptosis in a part of SMC hyperchromic neurons exposed to ischemia based on the presence of clear structural markers (decay of nuclei and cells; phagocytosis). For example, in layer III at 3 days, 6-12% of hyperchromic neurons underwent apoptosis, 13.4-24.6%  coagulation necrosis, and the remaining neurons came out of the pathological condition during a remote rehabilitation period. The proportion of irreversibly changed shadow cell was 11.5% (95% CI: 7.416.8%). During 30 days of the postischemic period, the numerical density of pyramidal neurons reduced by 30.5% (95% CI: 24.238.7%) in SMC layer III and by 14.4% (95% CI: 9.920.0%) in SMC layer V. Conclusion. The study demonstrated a mixed nature of neuronal death, a simultaneous combination of necrosis and apoptosis (parapoptosis). However, processes of immediate and remote ischemic necrosis played the major role in neuronal death.