Physical activity and environmental enrichment: Behavioural effects of exposure to different housing conditions in mice

Enriched environments and exercise provide complex environmental stimulation that can induce emotional and cognitive changes; however, few studies have evaluated the effects of these two components on other behaviours, such as novelty seeking or pain sensitivity. The aim of the present study was to investigate the influence of voluntary physical activity provided through different housing conditions on anxiety, locomotor activity, pain sensitivity, and exploration. Male mice at postnatal day (PND) 21 and were randomly assigned to one of four different conditions on PND 28: Marlau cages (MC), a standardized cage designed to provide a complex environment; physical exercise in large groups (PE-8); physical exercise in small groups (PE-4); or a standard environment (SE). After seven weeks, animals were evaluated in the hole-board task, the elevated zero maze, actimeter, and hot plate test. In the hole-board task, MC animals displayed more exploration than animals in the PE-8 and PE-4 groups, but no significant differences were observed between groups in the actimeter. In the elevated zero maze, MC and PE-8 animals exhibited an anxiogenic-like profile as compared to the SE group. When pain sensitivity was evaluated, the PE-8 group displayed a higher sensitivity to noxious thermal stimuli than the SE group. These data suggest that the complexity of the environment in which physical activity and environmental stimulation are provided can influence animal behaviours such as novelty seeking, emotional response, and pain sensitivity. These animal models could be useful for designing more personalized interventions that include physical, social, and cognitive stimulation to promote a more active lifestyle in humans. Such interventions could be useful in the prevention and treatment of aging-related decline or neurodegenerative diseases.