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

Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain

Brain Derived Neurotrophic Factor (BDNF) is a key molecule involved in plastic changes related to learning and memory. The expression of BDNF is highly regulated, and can lead to great variability in BDNF levels in healthy subjects. Changes in BDNF expression are associated with both normal and pathological aging and also psychiatric disease, in particular in structures important for memory processes such as the hippocampus and parahippocampal areas. Some interventions like exercise or antidepressant administration enhance the expression of BDNF in normal and pathological conditions. In this review, we will describe studies from rodents and humans to bring together research on how BDNF expression is regulated, how this expression changes in the pathological brain and also exciting work on how interventions known to enhance this neurotrophin could have clinical relevance. We propose that, although BDNF may not be a valid biomarker for neurodegenerative/neuropsychiatric diseases because of its disregulation common to many pathological conditions, it could be thought of as a marker that specifically relates to the occurrence and/or progression of the mnemonic symptoms that are common to many pathological conditions.

Effect of Crocin, Exercise, and Crocin-accompanied Exercise on Learning and Memory in Rats under Chronic Unpredictable Stress

Background:

Stress affects brain functions and induces psychological disorders. Previous studies have indicated different effects of crocin and exercise on the improvement of memory in some types of stress. The present study investigated the effect of crocin, exercise, and crocin-accompanied exercise on learning, memory, and memory consolidation in rats under chronic unpredictable stress (CUS).

Materials and Methods:

Male rats were randomly allocated to different groups: control, sham, stress, stress-exercise, stress-crocin, and stress-crocin-accompanied exercise groups. The CUS and treadmill running were applied 2 h/day and 1 h/day, respectively, for 21 days. Crocin (30 mg/kg) was daily intraperitoneally injected to the rats and their behavioral variables were evaluated as a brain function using the passive avoidance test.

Results:

Results showed that the CUS significantly decreased learning and memory compared to the control group, while crocin alone and crocin-accompanied exercise significantly improved learning and memory compared to the stressed group. It was found that exercise alone caused learning but did not improve memory in unpredictable stress rats.

Conclusion:

The data indicated that unpredictable stress had very destructive effects on the brain functions. Furthermore, unlike exercise, crocin improved memory under unpredictable stress conditions. Overall, it seems that the beneficial effects of crocin-accompanied exercise on learning and memory were probably because of crocin, but not exercise.

Effects of Crocin on Learning and Memory in Rats Under Chronic Restraint Stress with Special Focus on the Hippocampal and Frontal Cortex Corticosterone Levels

Background:

Chronic stress adversely influences brain functions while crocin, as an effective component of saffron, exhibits positive effects on memory processes. This study investigated the effects of different doses of crocin on the improvement of learning and memory as well as corticosterone (CORT) levels in the hippocampus and frontal cortex of rats subjected to chronic stress.

Materials and Methods:

Forty male rats were randomly allocated to five different groups (n = 8): Control, sham; stress (6 h/day for 21 days) groups, and two groups receiving daily intraperitoneal injections of one of two doses (30 and 60 mg/kg) of crocin accompanied by 21 days of restraint stress. Latency was evaluated as a brain function using the passive avoidance test before and one-day after a foot shock. CORT levels were measured in the homogenized hippocampus and frontal cortex.

Results:

Results revealed that chronic stress had a significantly (P < 0.01) negative effect on memory. Crocin (30 and 60 mg/kg), however, gave increase to significantly (P < 0.01 and P < 0.05; respectively) improved memory functions in the stressed rats. Furthermore, the CORT levels in the hippocampus and frontal cortex declined significantly (P < 0.05) in the stress group compared to the control. Only a crocin dose of 30 mg/kg was observed modulate significantly (P < 0.05) the CORT levels in the hippocampus and frontal cortex in the stressed group.

Conclusions:

It was found that the lower crocin dose (30 mg/kg) had more beneficial effects than its higher (60 mg/kg) dose on learning and memory under chronic stress conditions. Moreover, it was speculated that different doses of crocin act on different neurotransmitters and biochemical factors in the brain.