Differential expression of MAPKs subgroup in the hippocampus of rats exposed to chronic unpredictable stress

Abstract

Objective To examine the cognitive function and the differential expression of mitogen-activated protein kinase (MAPK) subgroup in the hippocampus of rats exposed to chronic unpredictable stress. Methods Thirty-two SD rats were divided into chronic unpredictable stress (CUS) group and controls. CUS rats were exposed to 21 days chronic unpredictable stressors,and the controls were stress-free. Immediately after the last stressor,the cognitive function was tested using Morris water maze,and the protein levels of MAPK subgroup in hippocampus were detected by immunohistochemistry and western blot. Results The latencies of CUS and control rats differed significantly on the first 5 trial (F=5.258～10.225,P 0.05),and the number of times that rats crossed the removed hidden platform in CUS group was significantly fewer than that in the control group (1.8±0.5 VS 7.0±3.9,t=3.741,P<0.05). Immunohistochemistry showed that the labeling index of P-CREB was reduced in the dentate gyrus in CUS group compared with that in the control group. Western blot showed that CREB,ERK1/2,P-ERK1/2,P38,P-P38 and JNK levels had no statistical difference in hippocampus between the two groups. However,CUS significantly decreased P-CREB level [(13.6±8.3) % VS (36.0±14.5)%,t=3.792,P<0.05] and P-JNK level [(30.8±7.8) % VS (113.8±55.3) %,t=4.204,P<0.05] in the hippocampus. Conclusions Abnormal JNK-CREB cascade played important roles in the CUS,and the spatial memory of the CUS rats was reduced compared to control rats,but can be restored to the comparable level through training. Key words: Chronic unpredictable stress (CUS); Mitogen-activated protein kinase (MAPK); cAMP response element-binding protein (CREB); Hippocampus