Environmental enrichment (EE) consists of an animal management technique with temporal, physical, social and sensory strategies, aimed at offering a series of incentives that can increase comfort and adaptability, both physiological and psychological, of laboratory animals. The effects of EE can be assessed by exposing animals to different behavioral tests. Among its different applications, EE has been touted as a protective factor in the treatment of emotional stress-related disorders, such as anxiety. However, the benefits of EE on anxiety-related behaviors are not as clear as those induced by this procedure in other areas of the neurosciences. In this context, some of the mechanisms of action exerted by EE are supported by empirical research data, while others are just mere assumptions, requiring the need for additional research to further elucidate the processes by which the enriched environment exerts its behavioral effects, either as an anxiolytic agent or as an inoculated stressor. The purpose of the present study is: 1) to standardize a model of EE that can be easily used by investigators in the field, 2) to investigate the effects of EE vs. impoverished environment on the behavioral defensive responses - avoidance and escape - measured by the elevated T-maze (ETM) model in rats. These responses have been associated, respectively, with two anxiety disorders encountered in clinical practice, generalized anxiety disorder and panic disorder. To measure locomotor activity, after being tested in the ETM animals will be submitted to an open field. In addition, the study will investigate the neuroplastic changes resulting from chronic exposure to EE through FosB protein immunoreactivity. For that, adult male Wistar rats will be submitted or not to EE for a period of 1-3 weeks, tested in the avoidance or escape tasks of the LTE and open field, and then there will be a detailed immunohistochemical study to measure the immunoreactivity of FosB protein in brain areas related to anxiety. At last, to further verify if EE exposure acts as an inoculated stressor, plasma concentration of corticosterone will be measured in independent groups of animals exposed to EE and to impoverished environment.
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