Effects of different durations of chronic unpredictable mild stress on behaviors and neurogenesis of hippocampal dentate gyrus in adult rats

Abstract

Objective To explore the effect of different durations of chronic unpredictable mild stress (CUMS) on behaiviors and neurogenesis of bippocampal dentate gyrus in adult rats.Methods (1)Animals were divided into four groups:control group,rats without stress; M1 group,rats subject to CUMS for 1 week; M2 group,rats subject to CUMS for 2 weeks; and M5 group,rats subject to CUMS for 3 weeks.(2) Rats'depression-like behaviors were observed in opening field test and 1％ sucrose preference test was done before and after the experiment of each group.(3) After bahavior test,rats were sacrificed and the hippocampi were isolated.Neurogenesis in hippocampal dentate gyrus was detected by using immunohistochemistry.Results (1) As compared with control group,total diatance (cm) in l0 min/center distance (cm) in 10 min/rearing counts were decreased in MI group (P ＜ 0.05),M2 group (P ＜ 0.05),and M3 group (P ＜0.05).There was no significant difference in the total distance in 10 min/center distance (cm) in 10 min/rearing counts among the M1,M2 and M3 groups (P ＞ 0.05).As compared with control group,levels of total fluid consumption/sucrose consumption/sucrose preference consumption were decreased in MI group (P ＜ 0.05),M2 group (P ＜ 0.05),and M3 group (P ＜ 0.05).There was no significant difference in levels of total fluid consumption among the M1,M2 and M3 groups (P ＞ 0.05) ; (2)As compared with control group (31.75 ± 8.48),BrdU-labeled cells in the dentate gyrus were decreased in M1 group (22.19 ±6.08) (P＜0.05) and M3 group (19.57 ±5.28) (P＜0.05),but there was no significant difference in the levels of BrdU-labeled cells in the dentate gyrus between M1 group and M3 group (P ＞ 0.05).There was no significant difference in the levels of BrdU-labeled cells in the dentate gyrus between M2 group (29.78 ± 6.78) and control group (P ＞ 0.05).Conclusion Different durations of CUMS could lead to the depressive behaviors,but have different influences on the neurogenesis of hippocampal dentate gyrus in adult rats. Key words: Chronic stress ; Hippocampus ; Depression ; Neurogenesis