ANALYSIS OF DIFFERENT TIMEFRAMES OF ENVIRONMENTAL ENRICHMENT ON THE BEHAVIOR OF ANIMALS MODEL OF SOCIAL ISOLATION-INDUCED STRESS

BACKGROUND: In order to reduce COVID19 infections, social distancing was implemented. Reports have shown that social distancing and isolation have increased stress, anxiety and depressive disorders. Environmental enrichment (EE) in experimental procedures involves altering housing patterns and provide exercise, exploration, and interaction with objects. It promotes stimulation of several brain areas. EE in stress models can improve cognition and reduce anxiety and depression-like behaviors. However, few studies have been investigating these potentials in models of isolation-induced stress. Therefore, the aim of this study is to investigate the effects of EE on behavior in isolated animals.

METHODS: Lister Hooded rats were used in this study and divided into 4 groups: standard, enriched, standard isolated and enriched isolated. Experimental procedures started at PND21 and two protocols were used in this study: 4 weeks of isolation followed by 1 week of EE (4SI+1EE) and 3 weeks of isolation followed by 2 weeks of EE (3SI+2EE). The cages were enriched with huts, tunnels and objects with different shapes. Behavioral parameters were evaluated using the Open Field (OF), Novel Object Recognition (NOR), Elevated Plus Maze (EPM) and Splash Test (ST). Results were quantified, and statistical analysis was performed using t tests.

RESULTS: Enriched grouped animals showed an increase in the cognitive skills (NOR) and reduced anhedonia-like behavior (ST) (3SI+2EE) as expected. Combination of enrichment and isolation induced anxiety-like behavior (OF) (3SI+2EE). Enrichment (4SI+1SE) or isolation (4SI+1SE and 3SI+2SE) reduced anxiety-like behavior.

CONCLUSIONS: The present data suggest an unexpected role of isolation, but a potential of EE in improving cognitive abilities and reducing anxiety and depressive-like behaviors. More assays are required to find out what could be underlying those effects of isolation which is controversy according to the majority studies.