Interactional effects of corticosterone and stress in the formation of PTSD-like memory impairment rats

Abstract

Objective To investigate the interactional roles corticosterone and stress played during the PTSD-Like memory impairment. Methods First we established the model of PTSD-like memory using three levels of electric shock: 0 mA, 0.8 mA and 1.4 mA. The freezing time percent of each group were calculated 24 hours later in order to find which group of rats obtained the PTSD-like memory, and generalizing tests was used to verify it. After the model was established, rats received adrenalectomy (ADX) were operated bilaterally in order to investigate the effect of corticosterone and fed with corticosterone in the drinking water 7 days before fear conditioning. These rats were divided into four groups: control group (no corticosterone supplement, 0 mA shock), Cort group (corticosterone supplement, 0 mA shock), shock group (no corticosterone supplement, 1.4 mA shock), Cort-shock group (corticosterone supplement, 1.4 mA shock). A two-way factorial analysis of variance was used to determine whether there was a significant interaction between corticosterone and shock. Results The freezing time percent of group 0.8 mA raised compared with the group 0 mA, whereas the freezing time percent of group 1.4 mA showed reversely and the generalizing effects appeared, compared with group 0.8 mA. In two-way factorial analysis design, the freezing time percent of Cort-shock group significantly increased (P<0.05) compared with other groups, and there was no significant variance among the other groups. Corticosterone (F=6.464, P<0.05) and stress (F=53.419, P<0.01) played parts in the formation of PTSD-like memory impairment, and they interacted with each other (F=11.580, P<0.05). Conclusion PTSD-like memory impairment can be induced on rats with high (1.4 mA) electrical shock, and they have interactional effect with each other in the process. Key words: PTSD-like memory impairment; Stress; Corticosterone; Fear memory