Early exercise promotes positive hippocampal plasticity and improves spatial memory in the adult life of rats.

There is a great deal of evidence showing the capacity of physical exercise to enhance cognitive function, reduce anxiety and depression, and protect the brain against neurodegenerative disorders. Although the effects of exercise are well documented in the mature brain, the influence of exercise in the developing brain has been poorly explored. Therefore, we investigated the morphological and functional hippocampal changes in adult rats submitted to daily treadmill exercise during the adolescent period. Male Wistar rats aged 21 postnatal days old (P21) were divided into two groups: exercise and control. Animals in the exercise group were submitted to daily exercise on the treadmill between P21 and P60. Running time and speed gradually increased over this period, reaching a maximum of 18 m/min for 60 min. After the aerobic exercise program (P60), histological and behavioral (water maze) analyses were performed. The results show that early-life exercise increased mossy fibers density and hippocampal expression of brain-derived neurotrophic factor and its receptor tropomyosin-related kinase B, improved spatial learning and memory, and enhanced capacity to evoke spatial memories in later stages (when measured at P96). It is important to point out that while physical exercise induces hippocampal plasticity, degenerative effects could appear in undue conditions of physical or psychological stress. In this regard, we also showed that the exercise protocol used here did not induce inflammatory response and degenerating neurons in the hippocampal formation of developing rats. Our findings demonstrate that physical exercise during postnatal development results in positive changes for the hippocampal formation, both in structure and function.

Increased basal plasma brain-derived neurotrophic factor levels in sprint runners.

OBJECTIVE: Exercise is known to enhance circulating brain-derived neurotrophic factor (BDNF) levels in healthy humans. BDNF changes have been measured in endurance but not in strength exercise. The present study aimed to investigate whether anaerobic activity such as sprinting differentially alters basal plasma BDNF concentration. METHODS: Brazilian sprinters (100 m) at either the international (Olympics and Outdoor World Championships) (n = 14) or the domestic level (n = 8), and sedentary subjects (n = 15), were recruited. Plasma BDNF concentrations were analyzed by enzyme-linked immunosorbent assay. RESULTS: The basal plasma BDNF concentrations were significantly higher in the international and the domestic sprinters than in the sedentary subjects. In addition, sprinters at the international level had higher plasma BDNF concentrations than those at the domestic level. CONCLUSION: Our findings suggest that increased basal plasma BDNF level is related to enhanced exercise performance.

Hippocampal mossy fiber sprouting induced by forced and voluntary physical exercise.

Alterations in the function and organization of synapses have been proposed to induce learning and memory. Previous studies have demonstrated that mossy fiber induced by overtraining in a spatial learning task can be related with spatial long-term memory formation. In this work we analyzed whether physical exercise could induce mossy fiber sprouting by using a zinc-detecting histologic technique (Timm). Rats were submitted to 3 and 5days of forced or voluntary exercise. Rat brains were processed for Timm's staining to analyze mossy fiber projection at 7, 12 and 30days after the last physical exercise session. A significant increase of mossy fiber terminals in the CA3 stratum oriens region was observed after 5days of forced or voluntary exercise. Interestingly, the pattern of Timm's staining in CA3 mossy fibers was significantly altered when analyzed 12days after exercise but not at 7days post-exercise. In contrast, animals trained for only 3days did not show increments of mossy fiber terminals in the stratum oriens. Altogether, these results demonstrate that sustained or programmed exercise can alter mossy fiber sprouting. Further Investigations are necessary to determine whether mossy fiber sprouting induced by exercise is also involved in learning and memory processes.