Quantitative Morphology of Neurons in Hippocampus and Dentate Gyrus of Etoposide-administered Male Wistar Albino Rats

Introduction: Chemotherapy can exert adverse effects on the central nervous system, like neuronal damage, which is characterized by increased apoptosis and reduced neurogenesis, contributing to cognitive impairment, such as learning and memory, and other executive functions. Objectives: To identify the degenerated neurons and quantify the viable neurons in different regions of the hippocampus and dentate gyrus (DG) in etoposide-injected rats and compare them with the normal control (NC) group. Materials and Methods: The study was carried out in Wistar Albino rats, which were divided into two groups, etoposide administered group ( n = 6) and NC ( n = 6). Etoposide was administered intraperitoneally at 45 mg/kg body weight. Neuronal visualization of the brain tissues stained with the cresyl violet stain was done under the light microscope, at low power. An area of 150 × 150 µm was selected for the DG and 250 µm length area for the different hippocampal regions (cornu ammonis regions 1-4). Results: There was a highly significant decrease in the number of viable neurons in the etoposide-administered rats when compared to NC in the different regions of the hippocampus. The neurodegeneration was obvious in morphology, as there were apoptotic changes with features of degenerated neurons, like shrunken neurons with hyperchromatic nuclei and pyknotic nuclei. However, etoposide administered group showed no significant difference in the neuron count and morphology, when compared to the NC group at the DG. Conclusion: The present study observed the neurotoxic effect of etoposide in the different regions of the hippocampus. There was no statistically significant difference observed in the quantity of viable neurons at the DG. However, this study has a limited number of study groups, and a single dose of etoposide is being administered. The results can be better interpreted with multiple doses of etoposide and a greater number of study groups.