Loganin ameliorates depression-like behaviors of mice via modulation of serotoninergic system

Rationale Depression is a serious neuropsychiatric disorder, which is characterized by sustaining mood disorders. Loganin, a major iridoid glycoside from Corni fructus, has a variety of pharmacological activities, including neuroprotective effect and hypnotic effect. However, little is known about the effects of loganin on stress-induced depression. Objective To investigate the effects of loganin on behavioral despair of mice, and whether serotonin (5-HT) and/or noradrenaline (NE) are involved in this process. Methods We tested the effectiveness of loganin using tail suspension test (TST). The possible mechanism was explored using reserpine-induced ptosis and hypothermia, and 5-HTP-induced head-twitch response in mice. The changes of 5-HT and NE in the prefrontal cortex, hippocampus, and striatum were measured through high-performance liquid chromatography (HPLC) analysis. Then, we identified the effects of depleting 5-HT and NE by PCPA (p-chlorophenylalanine) and DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride) pretreatment, respectively. Results Loganin (12.5/50 mg/kg) induced antidepressant-like effects in mice submitted to TST. Loganin (12.5/50 mg/kg) ameliorated the reserpine-induced hypothermia and ptosis, as well as increased 5-HTP-induced head-twitch responses in mice. Loganin (50 mg/kg) significantly increased the levels of 5-HT in the prefrontal cortex, hippocampus, and striatum. Furthermore, only PCPA treatment could eliminate loganin-induced antidepressant-like effects in TST. Conclusion Loganin exerts antidepressant-like effect in the TST depending on 5-HT levels in the central nervous system, which provide a potential agent for depression therapy.