Effect of forced exercise and exercise withdrawal on memory, serum and hippocampal corticosterone levels in rats

Abstract

Evidence suggests that there are positive effects of exercise on learning and memory. Moreover, some studies have demonstrated that forced exercise plays the role of a stressor. This study was aimed at investigating the effects of different timing of exercise and exercise withdrawal on memory, and serum and hippocampal corticosterone (CORT) levels. Wistar rats were randomly divided into five groups: control, sham, exercise-rest (exercise withdrawal), rest-exercise (exercised group), and exercise-exercise (continuous exercise). Rats were forced to run on a treadmill for 1 h/day at a speed 20-21-m/min. Memory function was evaluated by the passive avoidance test in different intervals (1, 7 and 21 days) after foot shock. Findings showed that after the exercise withdrawal, short-term and mid-term memories, had significant enhancement compared to the control group, while the long-term memory did not present this result. In addition, the serum and hippocampal CORT levels were at the basal levels after the rest period in the exercise-rest group. In the rest-exercise group, exercise improved mid- and long-term memories, whereas continuous exercise improved all types short-, mid- and long-term memories, particularly the mid-term memory. Twenty-one and forty-two days of exercise significantly decreased the serum and hippocampal CORT levels. It seems that exercise for at least 21 days with no rest could affect biochemical factors in the brain. Also, regular continuous exercise plays an important role in memory function. Hence, the duration and withdraw of exercise are important factors for the neurobiological aspects of the memory responses.

The Effect of Preventive, Therapeutic and Protective Exercises on Hippocampal memory Mediators in Stressed Rats

“…In other researches as well as our previous studies, it was reported that the CORT level crossed from the blood brain barrier (BBB) to brain with some limitations. Hence, the hippocampal CORT levels followed the serum CORT levels (2,13,32). In addition, the present findings confirmed that the protective and particularly the therapeutic exercises produced no significant decreases in the hippocampal CORT levels compared to the control group (Figure 1).…”

“…Accordingly, exercise could alter brain functions in the stressful conditions and neurodegenerative diseases (4)(5)(6)(7)(8)(9). It is demonstrated that stress and exercise affect the secretion of glucocorticoids hormones (corticosterone in rats; CORT) from the adrenal glands (2,(10)(11)(12)(13). In addition, glucocorticoids hormones can change some neuromodulators in the brain, such as interleukin-1 beta (IL-1β) (14), glucose (15), brain-derived neurotrophic factor (BDNF) (16), and other biochemical factors.…”

Acute exercise inhibits gastric emptying of liquids in rats: influence of the NO-cGMP pathway

“…The obtained plasma corticosterone results from sedentary rats are similar to those described by other authors with rats in hydromineral balance (22). Radahmadi et al (28) previously reported a similar increase in serum corticosterone levels in trained rats. Intracerebroventricular injection of CRF also delayed GE, and this effect was abolished by peripheral administration of CRF receptor antagonists (29).…”

“…Several peptides and hormones present in the enteroinsular axis play significant roles in body homeostasis, and their secretion is altered by physical exercise (28). In this sense, the metabolic effects of corticosterone are modulated by internal and external environmental conditions (29).…”

“…According to MacLaren et al (38), acute exercise, such as endurance exercise and forced swimming, raises blood VIP levels. In addition to eliciting splanchnic hyperemia, VIP also stimulates lipolysis, glycogenolysis, and gluconeogenesis, favoring energy mobilization during physical activity (28). In the present study, pretreatment with a VIP receptor antagonist inhibited the acute exercise-induced GE delay in awake rats.…”