Influence of chronic corticosterone injection on depression-like behavior and brain glycogen levels in mice

AIM: To study the effect of chronic corticosterone (CORT) injection on the depression-like behaviors and the brain glycogen level in mice. METHODS: Male C57BL/6N mice (n=40) were randomly divided into normal control group and model group. The mice in model group were subcutaneously consecutively injected with CORT for 4 weeks. The mouse model of chronic stress depression was constructed. The forced swim test and open field experiment were conducted to prove chronic stress model. The serum level of CORT in the mice was measured by radioimmunoassay. The protein levels of hippocampal synaptophysin (SYP) and brain-derived neurotrophic factor (BDNF) were detected by Western blot. Hippocampus glycogen, glycogen synthase and glycogen phosphorylase were determined by indirect fluorescence measurement. RESULTS: Compared with normal control group, the immobility time of the forced swim test in model group was significantly lengthened (P<0.01), and the ability of spontaneous activity was reduced (P<0.01), indicating that chronic CORT injection induced depression-like behaviors in mice. The CORT level increased significantly (P<0.01) in model group. CORT injection decreased the protein expression of hippocampal SYP and BDNF (P<0.01), reduced hippocampal glycogen level (P<0.05) and glycogen synthase activity (P<0.05), and increased glycogen phosphorylase activity (P<0.05). CONCLUSION: Chronic CORT injection causes hippocampal neuron damage and induces the depression-like behaviors of mice, which may be associated with decreasing hippocampal glycogen level by CORT.