Mechanism of action involved in the anxiolytic-like effects of Hibalactone isolated from Hydrocotyle umbellata L.

BACKGROUND AND AIM: Hibalactone (HB) is a lignan related to the anxiolytic-like effects of Hydrocotyle umbellata L. However, there is a need to understand better the mechanism of action of this lignan to support the ethnopharmacological uses of the species. This work aimed to evaluate by in vivo and in silico analysis the mechanism of action of HB involved in its anxiolytic-like effects. EXPERIMENTAL PROCEDURE: The effects of HB in mice were evaluated on light-dark box (LDB) and elevated plus maze (EPM) tests. The participation of 5-HT(1A) receptor and the benzodiazepine site of GABA(A) receptor was evaluated to investigate the possible mechanism of action. In silico tools were used to better elucidate the anxiolytic-like effects of HB. RESULTS: Oral treatment with HB at a dose of 33 mg/kg showed an anxiolytic-like effect in the LDB and EPM tests. Besides that, the treatment altered the ethological parameters, frequency of head dips, and stretched-attend postures (SAP), important to better describe the anxiolytic profile of HB. Pretreatment with flumazenil (2 mg/kg) reverted the anxiolytic-like effect of HB on LDB and EPM tests. On the other hand, pretreatment with NAN-190 (0.5 mg/kg) not reverted the activity observed. In silico predictions revealed the potential of HB to increase GABAergic neurotransmission. Pharmacophore modelling and docking simulations showed that HB might interact with the α1β2γ2 GABA(A) receptor. CONCLUSION: Together, the results presented herein suggest that activation of the benzodiazepine site of the GABA(A) receptor contributes to the anxiolytic-like effect of HB.