Effects of increased opportunity for physical exercise and learning experiences on recognition memory and brain-derived neurotrophic factor levels in brain and serum of rats

Studies with animal models showed that cellular, structural, and behavioral changes induced by environmental enrichment are related to increased levels of brain-derived neurotrophic factor (BDNF) in the brain. These evidence suggest that BDNF could be an interesting biomarker of the effects of lifestyle on cognition and other behavioral parameters in humans, mainly if the BDNF alterations in brain are accompanied by correspondent peripheral modifications, since human studies depend basically on the evaluation of this neurotrophin in serum or plasma. To test this hypothesis, we analyzed the effects of environmental enrichment on long-term memory for object recognition and on BDNF levels of hippocampus, frontal cortex, and serum of rats exposed to an experimental protocol that could be more easily translated to human intervention studies. Animals were maintained for 10 weeks in a social (standard laboratory conditions) or enriched (increased opportunity for physical exercise and learning experiences) condition. In the 7th week, they were submitted to behavioral testing (open field and novel object memory task), and at the end of the 10th week, they were killed and BDNF levels were analyzed. Animals maintained in the enriched condition showed enhanced performance on the memory task in the absence of any significant alteration in central or peripheral BDNF levels. The results of this study are important to highlight the need to develop experimental protocols using animal models that more closely resemble the characteristics of studies with humans and motivate more investigations to determine the conditions under which BDNF could be a biomarker of the effects of environment enrichment.