Ginkgo biloba modulates hippocampal BDNF expression in a rat model of chronic restraint stress-induced depression

Introduction: Mood disorders such as depression and anxiety disorders have been affecting a relatively high proportion of the world's population. Neuroplasticity hypothesis of depression proposes that lack of brain-derived neurotrophic factor (BDNF) can cause structural changes in the brain. The extract of Ginkgo biloba (Gb) leaves can restore much of the damage in the nervous system. We examined the antidepressant role of Gb extract (EGb 761) on BDNF expression modulation in the hippocampus of rats subjected to repeated restraint stress (RRS). Methods: Adult male rats were randomly divided into 10 groups: control, control-vehicle treated, stress, stress-vehicle treated, as well as three control and three experimental groups pretreated with EGb (15, 30, 60mg/kg, IP daily) for 21 days. They underwent restraint stress on a daily basis, 6 hours for 21 consecutive days. Weight changes, locomotor activity and forced swim test (FST) were employed to assess depressive-like symptoms. The serum corticosterone level was also measured by ELISA. Hippocampal BDNF DNA methylation and protein expression were assayed by methylation sensitive restriction enzymes (Real Time PCR) and Western-blotting respectively in all groups. Results: Pre-treatment with 30 and 60 mg/kg/day of Gb extract significantly attenuated depressive-like effects in the body weight, FST and serum corticosterone level in RSS rats compared to control groups. Further, it inhibited chronic stress-induced alterations in the hippocampal BDNF DNA methylation and protein expression. Conclusion: These findings suggest that Gb can induce an antidepressant role through its modulation effect on the hippocampal BDNF expression.