The Effect of Continuous Stress on Spatial Learning and Memory, Anxiety-Like Behavior, and Depression in Male NMRI Mice

The present study examined the effect of continuous immobilization stress on anxiety-like behavior, spatial learning and memory, and a forced swim test in NMRI male mice. The plasma cortisol changes and the brain-derived neurotrophic factor (BDNF) were also evaluated. The male NMRI mice were divided into control and stress groups (n = 10/group). The stress group was placed in restrained PVC tube for 360 min. Twenty-four hours later, the mice were tested for spatial learning and memory, anxiety-like behavior, and depression using the Barnes maze, an elevated plus maze, and a forced swim test, respectively. Also, the plasma cortisol level and the brain BDNF content were assessed by the ELISA method. Results indicated that the mice in the stress group had an elevated plasma cortisol level. There were no differences between the stress and control groups in the time taken and the distance traveled to reach the target hole. The animals in the stress group spent more time in the open arms of the maze and in entering the open arms, compared to the control group. Continuous immobilization stress caused a significant decrease in swim time for the animals in the stress group, compared to the control group. The brain BDNF concentration also found to be significantly in the stress group than the control group. In conclusion, acute sustained stress increases the brain BDNF level. It can facilitate anxiety-like behavior and depression, which may be due to a plasma glucocorticoid increment. However, the stress does not affect spatial learning and memory. © 2020, The National Academy of Sciences, India.