Environmental enrichment as a strategy: Attenuates the anxiety and memory impairment in social isolation stress

• Published in: International journal of developmental neuroscience Vol. 82; no. 6; pp. 499 - 512
• Main Authors: Keloglan Musuroglu, Seval, Ozturk, Duygu Murat, Sahin, Leyla, Cevik, Ozge Selin, Cevik, Kenan
• Format: Journal Article
• Language: English
• Published: 01.10.2022
• Subjects: environmental enrichment; hippocampus; learning and memory; social isolation
• ISSN: 0736-5748; 1873-474X
• DOI: 10.1002/jdn.10205

Background Social isolation (SI) early in life produces behavioral and cognitive abnormalities. On the contrary, environmental enrichment (EE) offers beneficial effects on brain plasticity and development. This study was designed to examine how EE affects memory functions, anxiety level, and the expression levels of memory/anxiety‐related genes such as NR2A, NR2B, BDNF, and cFos in the hippocampus of socially isolated rats. Materials and Methods Wistar albino male rats (n = 40) were separated into the five groups: Standard cage (SC), SI, EE, SI + SC, and SI + EE group. For each group, eight rats were housed, either grouped or isolated, in a standard or 3‐week EE, respectively. Morris water maze test (MWMT) was used for measuring the learning and memory function. Elevated plus maze (EPM) and open field (OF) were used for the evaluation of anxiety behavior. Blood corticosterone level was evaluated by the ELISA method. The expression levels of genes were measured by the RT‐PCR method. Results Results showed that EE increased memory performance in the SI group (p < 0.05). SI caused anxiety while EE improved anxiety behavior (p < 0.05). There was no significant difference between the groups in the OF test. Corticosterone levels did not change between groups. BDNF expression level was downregulated in EE and SI + SC compared with the SC group (respectively; p = 0.012; p = 0.011). NR2A, NR2B, and cFos expression levels did not change between groups significantly. Conclusions SI impaired memory performance while EE has beneficial effects on memory in socially isolated rats. EE alone was insufficient to cause alterations in the memory performance. The therapeutic effects of EE became strengthened while applied together with stress protocol. Together with improving the effectiveness of memory function, EE has the potential to decrease anxiety behavior. EE seemed to be the reason for decreasing in BDNF. In this study, we examined the effects of environmental enrichment on memory and anxiety in social isolated male rats. We also focused on hippocampal gene expression related with memory function. Environmental enrichment increased the memory function and decreased anxiety behavior. On the other hand, social isolation decreased memory function and increased anxiety. Together with these findings, environmental enrichment decreased the BDNF gene expression level.