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Ahmad Rahmani

Ahmad Rahmani, Naser Naghdi
Mild Treadmill Exercise can alleviate Stress-induced impairment in Cognitive function
Abstract


Chronic stress can increase the levels of adrenal glucocorticoids resulting in changes on cognitive functioning. Literatures display that although some degrees of stress can be helpful, but, in term of its type, intensity, and duration, it can also cause some negative effects on learning and memory.  The hippocampus, a critical structure for spatial learning and memory, is particularly vulnerable to stress-induced glucocorticoid damage, reflected as deficits in spatial memory tasks and synaptic plasticity. Excessive exposure to glucocorticoids can induce neuronal damages, particularly in the hippocampus, a region enriched with corticosteroid receptors. On the other hand, exercise has been considered as a factor to relieve stress side effects. But, variation in exercise protocols (forced vs. voluntary) and intensities have had different results. In the present study we evaluate the hypothesis that immobilization stress can affect learning and memory, and mild exercise can protects against stress-induced function deficit.   Adult male albino Wistar rats (2300–250 g) obtained from Pasteur Institute of Iran were housed in a temperature (25±2 ◦C) and humidity-controlled room. The animals were maintained under a 12:12 h light/dark cycle, with lights off at 7:00 p.m. Food and water provided ad libitum. All experimental procedures were in accordance with the NIH Guide for the Care and Use of Laboratory Animals. The animals were randomly assigned into the Immobilization stress, Exercise-Stress, Exercise, and Control groups (11 in each). all tests were carried out during the light phase. Subjects underwent immobilization stress (2 h per day × 7 day), mild intensity treadmill exercise (30 min. per day × 7 day), or no interventions. The statistical analysis of the data was carried out by one-way and repeated measure of ANOVA, and unpaired t-test. In all comparisons, p≤0.05 was considered significant. Serum corticosterone levels were measured in the rats at baseline (11:00 h) and immediately following the immobilization treatment (13:00 h) on the first and last days of the stress treatment. As was expected, Stressed rats had significantly elevated levels of corticosterone at the post-stress time (P< 0.001). On the other hand, exercise had significant effect on decrement of corticosterone levels (p<0.001). Chronic immobilization stress significantly impaired learning (p < 0.01) and memory (p<0.05) comparing with unstressed animals. There was no significant difference in the swimming speed between these groups. In non-stressed rats, despite the lack of difference between sham and exercise groups, in acquisition stage, treadmill exercise enhanced performance in recall (p< 0.05). Stress can impair cognitive function. While, mild exercise has protective effect on stress-induced learning and memory loss. Corticosterone may be a major mediator in the protective effect of exercise against stress-induced cognitive impairment.  In addition, beneficial effects of exercise on cognitive performance continue to evolve even after exercise has ended.  

 

 

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