Expression of S100B in hippocampus of depression model rats induced by chronic unpredictable stress and the effect of fluoxetine in bolcking it

Abstract

Objective To explore the relationship between expression of S100B in hippocampus of depression model rats induced by chronic stress and its depression like behavior, and the antidepressant effect of fluoxetine. Methods 40 rats were put into control group, fluoxetine group, CUS group and CUS plus fluoxetine group, using random number table. Rats in each groups received corresponding treatment. Chronic unpredictable stresses(CUS) were performed on rats for 42 days. Fluoxetine(5 mg/(kg·d)) were delivered to rats by intragastric administration from day 22 to day 42. Then, S100B protein were marked and observed by immunohistochemical method. Open-field test, sucrose consumption and body weight were used to evaluate behavioral changes. Results Scores in behavioral test were reduced significantly by 42 days of stress (main effects of stress, P<0.05) . Effects of stress on behavioral scores were reversed by 21 days fluoxetine treatment (interactions, P<0.05). CUS resulted in elevated expression of S100B in CA1, CA3 and DG sub-regions in experimental rats (OD values, CUS, 0.331±0.01, 0.353±0.01, 0.381±0.007; control, 0.238±0.007, 0.237±0.010, 0.228±0.006. Simple effects of stress, P=0.000; P=0.000; P=0.000). Fluoxetine treatment reversed the elevated expression of S100B in CA1, CA3 and DG sub-regions in model rats (OD values: CUS plus fluoxetine, 0.233±0.015, 0.240±0.005, 0.254±0.015; fluoxetine, 0.241±0.007, 0.233±0.013, 0.227±0.017; Interactions between fluoxetine and CUS, P=0.000; P=0.000; P=0.000). Conclusion Sub-regional over expression of S100B in hippocampus is associated with depression like behavior of rats. Reversed S100B expression in these sub-regions is an indicator of effective antidepressant treatment but not a mechanism for it. Key words: Depression; Rats; Hippocampus; S100B; Fluoxetine