Effects of Dark- Light Cycle on the Histological and Immunohistochemical P73 Marker Expression of Cajal Cells in the Cerebral Cortex of Mice

Abstract

background:.The horizontal cells of Cajal are small, fusiform, horizontally oriented cells found in the most superficial layers of the cortex. A dendrite emerges from each end of the cell, and an axon runs parallel to the surface of the cortex, making contact with the dendrites of pyramidal cells. the express P73 on nuclear membrane. aim of study: To evaluate the morphometric histological analysis of Cajal cells in cerebral cortex and evaluate the thickness of gyri and sulci, according to stimulation of light and dark field. To evaluate the P73 marker expression of Cajal cells in the cerebral cortex according to stimulation of light and dark field of male Swiss Albino mice. materials and methods: Coronal sections were placed on standards glass slides for H&E staining, and on positively charged slides for immunohistochemical staining with P73, which was evaluated using Aperio Image Scope analysis software V9. There were significant difference in body weight between the experimental and Control groups. Light group had a higher body weight than the control and dark groups. The histological features in experimental group showed significant changes in the thickness of cerebral cortex especially the molecular layer, also change in the depth and width of gyri and sulci, these changes associated with cytoplasmic vacuolation, nuclear apoptotic.. Change in P73 expression in cerebral cortex, P < 0.05 revealed significant differences across groups. It showed the most expression in the control group, with a mean value of 0.43±0.25 , in light group it increased compared to other groups with mean value of 0.41± 0.13. results: The experimental animals of light group reveal high body weight than that of dark animals due to increase in food consumption. The experimental animals of light group reveal less sleep insomnia and overactive than that of dark animals. Although these animals became adapting to such daily disruption of light or dark field. they override the tendency of mice to sleep during the light phase. The experimental animals of light group reveal repellent, lonely, isolated living attitude and developed quarreling with aggressiveness behavior with each other in comparison to dark group mice that reveals more active and social behaviors. The thickness of whole layers and especially molecular layer of temporal lobe reveals a significant decrease in the light group in comparison to other animals this is due to indirect stressful effect of light on the nerves cells of cerebrum of experimental animals that induces more apoptosis and cells death than other groups. The study about the marker expression of P73 of the Cajal (CR) cells in the molecular layer of dark group mice reveals a significant increase in values who found that there were neuronal cells proliferation , migration and differentiation are more apparent in comparison to other groups. conclusions: this indicate that P73 has vital role in neuronal cells development in different parts of the brain.