Combined effects of royal jelly and environmental enrichment against stress-induced cognitive and behavioral alterations in male rats: behavioral and molecular studies

Exposure to chronic stress has detrimental effects on cognitive and emotional processing. Also, the neuroprotective influences of environmental enrichment (EE) and royal jelly (RJ) have been indicated in previous studies.To our knowledge, to date, there are no studies about the synergistic effects of EE and RJ on cognitive changes induced by stress. Therefore, this study aimed to investigate the protective effects of RJ, and EE on anxiety-like behaviors, cognitive functions, and expression of hippocampal and also prefrontal cortex (PFC) brain-derived neurotrophic factor (BDNF) levels in stressed rats.By using restraint and cold temperature, rats were exposed to stressful situations and then subjected to treatment with RJ or/ and EE for 14 days. Stress induction was done 14 days before treatments by placing the rats in the restrainer under 4°C. Following the interventions, anxiety-like behaviors, novel object recognition memory (NORM), inhibitive avoidance performance, hippocampal, and PFC BDNF expression were examined. The plasma corticosterone level of all groups was also evaluated.Results showed increased plasma corticosterone levels, stress-induced deficits in the NORM and IA tests, and increased anxiety-like behaviors. EE and RJ improved these deficits with a decline in serum corticosterone and also increased BDNF levels in the hippocampus and PFC in stressed ones.The EE and the RJ prevented the detrimental effects of stress on anxiety-like behaviors and memory processes. These treatments can protect susceptible brain areas against chronic stress via improvement in behavioral and cognitive impairments through mediating BDNF expression.