Effects Of Traumatic Stress Experience In Early Adolescence On Emotion And Cognitive Function In Rats

Objective:To explore the effects of early-adolescent traumatic stress on rats’ emotion and cognitive function as well as the mechanism when they grow up.Methods:Early-adolescent male Wistar rats were randomly divided into control group and stress group. The traumatic stress animal model was built by electric foot shock stress. Open field test, the elevated plus maze and the Morris water maze were used to test the emotional and cognitive functional alterations. HPA axis reactivity and the level of plasma corticosterone were evaluated by the dexamethasone-suppression test (DST) and radioimmunoassay. Corticotropin-releasing factor receptor type-1(CRF1) expression in Hippocampus and amygdala was detected using Immunohistochemistry and Western blotting.Results:The stress group exhibited more anxiety-like behaviors(P<0.05) by showing less rearing and less time spent in central zone in open field test; less time spent in open arms and more droppings pellets in elevated plus maze test. The stress group exhibited an impairment of learning and memory, taking longer latency time to platform on day2in the Morris water maze compared to the control group. Stress group had a dysregulation of HPA axis as plasma corticosterone could not be suppressed in DST compared with control group. CRF1expression in amygdala was significantly up-regulated in the stress group (P<0.05). CRF1expression in Hippocampus was significantly down-regulated in the stress group (P<0.05).Conclusions:1. Traumatic stress experience in early adolescence may induce anxiety.2. Traumatic stress experience in early adolescence may result in learning and memory impairment.3. Upregulation of CRF1in amygdala, downregulation of CRF1in hippocampus and dysregulation of HPA axis are associated with learning and memory disorders and the higher level of anxiety of the stress group.