RESUMO
Objective To explore the effect of long-term chronic mild stress on depression-like behaviors and the expression of heat shock protein 70(HSP70) in rats.Methods The standard SD rats were divided into two groups as following:one group (n =6) was treated with chronic mild stress for 3 weeks,and another group (n =5) was treated with chronic mild stress for 6 weeks.Depression-like behaviors of rats was observed by sucrose consumption test and open field test before and after chronic mild stress.And Western Blot,RT-PCR and immunohistochemistry were utilized to detect the HSP70 expression in the hippocampus and frontal lobes of rats after chronic mild stress.Results The sucrose favoritism in sucrose consumption test,the scores of crossing and the time for rats' retention in the center grid of open field test in long-term group were higher than those in short term group(P＜ 0.05).HSP70 expression in the hippocampus and frontal lobes of long-term group (0.81 ± 0.08,0.85 ± 0.08)detected by Western Blot and immunohistochemistry was higher that of short-term group (0.60 ± 0.06,0.85 ±0.07).HSP70 expression in the hippocampus of long-term group (0.90 ± 0.05,1.37 ± 0.38)detected by RT-PCR was higher that of short-term group(0.78 ± 0.04,1.08 ± 0.14) (P ＜ 0.05).Conclusion After long-term chronic mild stress,the depression-like behaviors decrease,and at the same time HSP70 mRNA and protein increase.