[Correlation between Depressive Behavior and Expressions of S100β and Brain-derived Neurotrophic Factor in Hippocampus and Frontal Cortex of Rats].

Objective To investigate the association between chronic unpredictable mild stress (CUMS)-induced depressive-like behavior in rats and expressions of brain-derived neurotrophic factor (BDNF) and S100β in the hippocampal and prefrontal cortex. Methods Rats were randomly assigned to three groups:saline control group,saline+CUMS group,and citalopram +CUMS group. CUMS was used for depression modeling in rats. Depressive-like behavior in rats were evaluated by open-field test,sucrose preference test,and novel object recognition test. S100β and BDNF expressions were tested by enzyme-linked immunosorbent assay. Results Rats in the saline+CUMS group had significantly lower score in sucrose preference [(52.48±13.14)%],basic motor tasks [(845.8±371.4)s],fine motor tasks [(565.6±211.9)s],and longer resting time [(282.6±11.8)s] compared to the control group [(84.30±6.15)% (t=7.49,P=0.000),(1239.1±281.6)s (t=2.83,P=0.008),(801.8±150.9)s (t=3.05,P=0.003),(268.2±12.8)s (t=2.72,P=0.001)]. Compared with the citalopram+CUMS group,rats from the saline+CUMS group also showed significantly lower results in sucrose preference [(80.55±11.31)%,t=5.39,P=0.000],basic motor tasks [(1156.4±314.7)s,t=2.13,P=0.031],and fine motor tasks [(736.1±150.0)s,t=2.21,P=0.008]. There were no significant differences in the expression of hippocampal and prefrontal BDNF between these two groups,but rats from the saline+CUMS group expressed significantly higher levels of S100β compared to rats from the citalopram+CUMS group [(13.22±2.23) ng/g vs. (10.55±2.72) ng/g,t=2.67,P=0.014]. Pearson correlation analysis revealed that the expression of S100β was positively correlated with the expression of BDNF in the prefrontal cortex and hippocampus (r=0.35,P=0.034;r=0.36,P=0.034).The novel object recognition index was positively correlated with the expression of BDNF in the hippocampus(r=0.38,P=0.021),and the duration of fine-motor activities was negatively correlated with S100β in the prefrontal cortex (r=-0.36,P=0.037). Conclusions Different types of depressive behaviors in rats induced by CUMS are associated with the selective expression of S100β and BDNF in two different brain cortex. S100β protein and BDNF may independently participate in the pathogenesis of depression.