Effect of Different Durations of Stress on Spatial and Cognitive Memory in Male Rats

Abstract

Background: Recent data have implicated stress as a risk factor in the development of neuropsychological disorders that impairs memory. Stress has different complex effects on memory. In other words, stress can increase or decrease the memory or has no effect on it. This study investigated different timing effects of stress on cognitive and spatial memory. Methods: In this study, 28 male Wistar rats were divided into four groups of 7, control, acute stress, middle stress, and chronic stress. Restraint stress was used to induce stress. In addition, memory function was evaluated via the novel object recognition (NOR) and object location (OLT) tests for estimating cognitive and spatial memory. At the end of the study, serum corticosterone levels were measured via enzyme-linked immunoassay (ELISA). Findings: In middle and chronic stress groups, the object exploration times during the NOR test session were significantly lower than control group (P < 0.001 and P < 0.05, respectively). There were no significant decreases in the time of object exploration during the test session of OLT task in all stressed groups compared to the control group. Corticosterone levels were significantly increased in middle and chronic stress groups compared to the control group (P < 0.01 and P < 0.05, respectively). Conclusion: Data correspond that chronic and especially middle stress impaired cognitive memory. Therefore, middle stress was the most deleterious stress model. On the other hand, acute, middle and chronic stress did not impair spatial memory in the OLT task. Therefore, different duration of stress was one of the most important factors in causing cognitive memory impairment.

Keywords

• Stress
• Cognitive memory
• Spatial memory
• Corticosterone
• Rat