Immediate and persistent antidepressant-like effects of Chaihu-jia-Longgu-Muli-tang are associated with instantly up-regulated BDNF in the hippocampus of mice

Conventional antidepressants have a disadvantage in delayed onset of efficacy. Here, we aimed to evaluate the immediate and persistent antidepressant-like action of a classic herbal medicine Chaihu-jia-Longgu-Muli decoction (CLM) as well as the action of CLM on hippocampal brain-derived neurotrophic factor (BDNF) over time. CLM consists of Xiaochaihu decoction (XchD), Longgu-Muli (LM) and several other herbs. The contribution of constituent herbal formula XchD and other parts of CLM was also assessed. Following a single dose of CLM, tail suspension test (TST), forced swim test (FST), and novelty-suppressed feeding test (NSF) were performed. The antidepressant activity of XchD, its interaction with LM or remaining parts of CLM was also examined after a single administration. BDNF expression in the hippocampus was examined at 30 min and 24 hr post a single CLM. A single administration of half of clinical dose of CLM elicited antidepressant effects at TST 30 min post administration, and lasted for 72 hr. Furthermore, CLM also reduced the latency to eat in NSF test. A single proportional dose of XchD induced antidepressant effects at 30 min and lasted for 48 hr, whereas the effect lasted for 72 hr when combined with either LM or the remaining parts of CLM. BDNF expression increased at 30 min and persisted at least for 24 hr after a single dose of CLM. The results support that Chaihu-jia-Longgu-Muli decoction was capable to immediately and enduringly elicit antidepressant activity via enhancement of hippocampal BDNF expression, in which the constituent Xiaochaihu decoction played the primary role.