Novel intranasal delivery of sihosogansan demonstrates rapid antidepressant activity via GABAergic and BDNF/TrkB pathways: identification of potential bioactive quality markers.

BACKGROUND: Sihosogansan (SHSGS) is a traditional medicine used to treat depression. However, conventional oral administration requires high doses and prolonged treatment periods. This study aimed to investigate the rapid antidepressant effects of intranasal SHSGS and to identify its Q-markers. METHODS: In zebrafish, SHSGS effects were evaluated in an MK-801-induced anxiety model using electroencephalogram (EEG) recordings. In mice, the rapid effects of intranasal versus oral SHSGS were compared through the open field and tail suspension tests. Mechanistic investigations combined computational network analysis with molecular studies of hippocampal tissue and primary neurons. Q-markers were identified through the integrative analysis of gas chromatography-mass spectrometry data, molecular docking, and experimental validation in behavioral and cellular models. RESULTS: SHSGS normalized MK-801-induced EEG abnormalities within 30 min in zebrafish, particularly restoring delta/beta and theta/beta ratios. In mice, intranasal SHSGS showed rapid anxiolytic and antidepressant effects at 30 min post-administration, whereas oral administration had no significant effect. SHSGS enhanced gamma-aminobutyric acid (GABA)ergic signaling by increasing hippocampal GABA type B receptor subunit 1, glutamate decarboxylase 67, and GABA levels, while activating the brain-derived neurotrophic factor/tropomyosin receptor kinase B/extracellular signal-regulated protein kinase (BDNF/TrkB/ERK) pathways. Three monoterpenes β-pinene, terpinen-4-ol, and α-terpineol were identified as bioactive Q-markers of SHSGS based on their consistent antidepressant-like effects across behavioral, cellular, and molecular assays. Inhibitor experiments further revealed that α-terpineol's action required GABA(B1) receptor signaling, while β-pinene and terpinen-4-ol showed indirect dependency on GABA(B1) receptor or TrkB pathways. CONCLUSION: These findings demonstrate that intranasal SHSGS acts rapidly against depression through the GABAergic and BDNF/TrkB/ERK pathways, with identified Q-markers providing a foundation for optimization of quality.