Immunohistochemical evaluation of c-Fos activity in Dentate gyrus of cranially irradiated mice

Abstract

Objectives: The main objective of the study was to test the c-Fos immunoreactivity in dentate gyrus along with the hippocampal dependent learning (HDL) and long-term memory functions (LMF) of cranially irradiated early postnatal mice at both short and long terms.Methods: The cranial/head regions of anesthetized mice were administered a dose of 8 Gray (Gy) in postnatal day 14 (P14) and assigned as radiation group (Rad). Additionally, a group of age and body weight matched mice were assigned as anesthetic (only given anesthesia) and normal control group (not exposed to any application). A portion of mice in all groups were decapitated and brains were removed at P22 for evaluation of early (acute) effects of CR. Additionally, seven months later, the remaining mice were first assigned for Open Field test (OF) to measure the locomotor activity, and afterwards for Morris Water Maze paradigm (MWM) to test the HDL and LMF for testing the long-term effects of CR. Following the behavioral tests, immunohistochemical stainings (im) were performed with c-Fos marker to test the number of active granular neurons at P22 (acute) and P231 (late) hippocampi as compared to the control counterparts.Results: In MWM, learning and memory patterns of Rad+ group were found to be significantly decreased as compared to the control groups (p<0.005). We found a significant decrease of c-Fos positive neurons at the subgranuler layer of dentate gyrus of Rad group as compared to the controls (p<0.005) at both P22 and P231 hipocampi. Conclusion: Overall, CR (in both long and short terms) reduced the neurogenesis c-fos immune-positive neurons while weakening the cognitive abilities such as learning and memory after early postnatal cranial irradiation.