Environmental enrichment (EE) has been studied as a protocol that can improve brain plasticity and may protect against negative insults such as chronic stress. The aim of this study was to evaluate the effects of EE on the hormonal and behavioral responses induced by chronic mild unpredictable stress (CMS) in rats, considering the involvement of the renin-angiotensin system. Male adult rats were divided into 4 groups: control, CMS, EE, and CMS + EE, and the experimental protocol lasted for 7 weeks. EE was performed during 7 weeks, 5 days per week, 2 h per day. CMS was applied during weeks 3, 4, and 5. After the CMS (week 6), depression-like behavior was evaluated by forced swimming and sucrose consumption tests, anxiety level was evaluated using the elevated plus-maze test, and memory was evaluated using the Y-maze test. On week 7, the animals were euthanized and basal plasma levels of corticosterone and catecholamines were determined. The hypothalamus was isolated and tissue levels of angiotensin peptides were evaluated. CMS increased plasma corticosterone, norepinephrine, and epinephrine basal concentrations, induced depression-like behaviors, impaired memory, and increased hypothalamic angiotensin I, II, and IV concentrations. EE decreased stress hormones secretion, depression-like behaviors, memory impairment, and hypothalamic angiotensin II induced by stress. Reductions of anxiety-like behavior and norepinephrine secretion were observed in both stressed and unstressed groups. The results indicated that EE seemed to protect adult rats against hormonal and behavioral CMS effects, and that the reduction of angiotensin II could contribute to these effects.

环境富集 (EE) 已被研究为一种可以改善大脑可塑性并可以防止负面侮辱（例如慢性压力）的协议。本研究的目的是评估 EE 对大鼠慢性轻度不可预测应激 (CMS) 诱发的激素和行为反应的影响，考虑到肾素 - 血管紧张素系统的参与。雄性成年大鼠分为4组：对照组、CMS、EE和CMS+EE，实验方案持续7周。EE 在 7 周内进行，每周 5 天，每天 2 小时。在第 3、4 和 5 周应用 CMS。在 CMS（第 6 周）后，通过强迫游泳和蔗糖消耗测试评估抑郁样行为，使用高架十字迷宫测试评估焦虑水平，并评估记忆力使用 Y 迷宫测试。在第 7 周，将动物安乐死并测定皮质酮和儿茶酚胺的基础血浆水平。分离下丘脑并评估血管紧张素肽的组织水平。CMS 增加血浆皮质酮、去甲肾上腺素和肾上腺素的基础浓度，诱发抑郁样行为，记忆力受损，并增加下丘脑血管紧张素 I、II 和 IV 浓度。EE 减少应激激素分泌、抑郁样行为、记忆障碍和由应激引起的下丘脑血管紧张素 II。在压力和非压力组中观察到焦虑样行为和去甲肾上腺素分泌减少。结果表明，EE 似乎可以保护成年大鼠免受荷尔蒙和行为 CMS 影响，并且血管紧张素 II 的减少可能导致这些影响。