Purpose: Episodes of acute emotional or physical stress can have significant adverse effects on the hippocampus. Ginsenoside Rb1, the most predominant ginsenoside present in Panax species, has been reported to show a neuroprotective effect. The purpose of this study was to investigate the influence of ginsenoside Rb1 on plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels and hippocampal brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) levels in rats subjected to acute immobilization stress.
Methods: Wistar rats  were divided into controls treated with saline only (N), rats exposed to stress only (M), and rats pretreated with Rb1 (40 mg.kg (−1)) thirty minutes prior to stress exposure (R). In the model, animals were restrained in a plastic immobilizer for 2 h of acute immobilization stress at room temperature. ELISA was used to determine plasma levels of CORT and ACTH. The effect of Rb1 pretreatment on the expression of BDNF and TrkB was determined by immunofluorescence, real-time PCR, and Western blotting analysis.
Results: The R group showed significantly increased plasma CORT and ACTH levels compared to the N and M groups. Acute stress stimulation suppressed BDNF and TrkB protein and mRNA expression in the hippocampus; otherwise, Rb1 pretreatment reversed the decreases.
Conclusion: The results from this study demonstrate that Rb1 pretreatment reverses the decreases in hippocampal BDNF/TrkB and increases the plasma levels of CORT and ACTH, indicating a potential neuroprotective effect of Rb1 against acute stress.
Keywords: ginsenoside Rb1, CORT; ACTH, acute immobilization stress, BDNF, TrkB