Impact of environmental enrichment on the GABAergic neurons and glucocorticoid receptors in the hippocampus and nucleus accumbens of Wistar rats: Pro-resilient effects.

The unpredictable chronic mild stress (UCMS) model has been used to induce depressive-like symptoms in animal models. Our work aims to evaluate the impact of environmental enrichment on male Wistar rats in an animal model for depression. For this purpose, we aim to assess changes in GR and GABAergic (PV+) density in cerebral regions related to cognitive-affective processes associated with depressive disorder, such as the dorsal- ventral hippocampus and accumbens nuclei. Three groups of rats were used: UCMs (unpredictable chronic mild stress), EE+ UCMs (enrichment + stress) and CONT (behavioral tests only). Hedonic responses elicited by sucrose solution were examined by licking behavior analysis; the anxiety level was evaluated using the elevated zero maze and the forced swimming (passive coping) tests. The environmental enrichment reduced the effects of chronic stress, promoting greater resilience. Thus, the UCMs group showed an anhedonia response, more anxiety and immobility behavior than either the control or the EE+ UCMs groups. Regarding immunochemistry results, there was a reduction in GABAergic activity coupled with increased activation of GR in UCMs in the dorsal hippocampus, but there were no differences between groups in the ventral hippocampus. These results suggest environmental enrichment could enhance greater resilience, reducing the vulnerability of the subjects to develop disorders such as depression and anxiety.