Enriched environment and exercise effects on parvalbumin expression and distribution in the hippocampal formation of developing rats.

Several models of environmental enrichment and physical exercise have been used to explore the experience effects on brain functions and plasticity, mainly in adult animals. In order to examine the early influence of these stimuli on developing brain, the present study used calcium-binding protein parvalbumin as neuroplastic marker in the hippocampal formation of male Wistar rats subjected to environmental enrichment or physical exercise from postnatal days 21 to 60 (P21-P60). In our study, no significant difference in hippocampal expression and distribution of parvalbumin was found between enriched and control rats. However, a significant increase in parvalbumin protein expression as well as in the number of neurons stained with parvalbumin was observed in the hippocampal formation of rats submitted to daily treadmill exercise when compared to the control rats. The hippocampal region with the highest number of parvalbumin neurons in exercised rats was Cornus of Amon 2 e 3 (CA2/CA3). These findings indicate that developing brain may be differentially sensitive to environmental stimulation models. Specifically, our results show that hippocampal expression and distribution of parvalbumin in developing rats may be more influenced by exercise than by enriched environment. The mechanisms are not yet known.