Possible GABAkine-Mediated Sedative-Like Antidepressant Effects of Phytol: Molecular Interventions Through In Vitro, In Vivo and In Silico Approaches

Abstract

Background: A previous report suggests that phytol (PHY) may exert its antidepressant effects in mice, possibly through GABA_A receptor interaction pathways.

Aim: We aimed to check its antidepressant effect with possible molecular mechanisms through behavioral and in silico studies.

Methods: For this, adult mice were randomly divided into different groups (n = 6), namely control (vehicle), standards (DZP: diazepam at 2 mg/kg, FLU: flumazenil at 0.1 mg/kg, FLUX: fluoxetine at 20 mg/kg), PHY (25, 50, and 75 mg/kg), and combined groups (PHY-75 with DZP-2 and/or FLU-0.1, and FLUX-20). Thirty minutes after treatment, each animal was subjected to tail suspension and forced swimming tests, and their immobility time (IMT) was counted for 5 min. In silico studies were performed with the GABA_A receptor α1, α2, α3, α5, and γ2 subunits and 5HT_1A to investigate possible molecular mechanisms. Additionally, in vitro GABA activity of PHY and/or reference drugs was also performed by using the colorimetric method.

Results: The results demonstrated that PHY and/or DZP significantly (p < 0.05) and concentration-dependently inhibited GABA, while FLU alone or its combination with PHY reversed it. In mice, PHY dose-dependently reduced the IMT in both protocols, while FLUX-20 showed lower IMT compared to the control and DZP, indicating elevated locomotion in mice. It showed a reduced IMT value in male animals than in female animals. In both sexes, PHY at 75 mg/kg significantly (p < 0.05) increased the IMT values with DZP-2, while reducing this parameter with FLU-0.1. In silico studies demonstrated that PHY exhibited higher binding affinities with the α2 and α3 subunits of the GABA_A and 5HT_1A receptors by -6.5, -7.2 and 6.7 kcal/mol, respectively.

Conclusion: Taken together, PHY exerted sedative-like antidepressant effects in mice and modulated the effects of GABAergic drugs DZP and FLU and serotonergic drug FLUX. PHY may be a potential candidate for the management of depression.

Keywords: GABAkine pathway; antidepressant effect; molecular docking; phytol.

FIGURE 1

The 2D chemical structures of the test sample and the reference drugs.

FIGURE 2

The 2D and 3D visualizations of the test sample and the reference drug interaction with the GABA_A receptor (α3 subunit).

FIGURE 3

Summary of physicochemical or drug likeness properties of selected compounds [The colored zone is the suitable physicochemical space for oral bioavailability; SIZE: 150 g/mol2 < TPSA< 130 Ų; FLEX (Flexibility): 0 < num. Rotatable bonds < 9].

FIGURE 4

Possible antidepressant mechanism of phytol through GABAergic and serotonin pathways. [This figure illustrates the antidepressant mechanisms of PHY on the GABAergic and serotonergic systems. PHY, in combination with DZP, enhances GABA_A receptor activity, leading to increased Cl⁻ influx into postsynaptic neurons. This influx causes hyperpolarization, which decreases neuronal excitability and produces antidepressant effect. Meanwhile, PHY enhances serotonin synthesis by acting on tryptophan hydroxylase and inhibited serotonin receptor signaling on presynaptic neurons. Together, these actions elevate serotonin levels, contributing to mood regulation. The figure suggests that PHY's GABAergic modulation and serotonergic enhancement produce a combined antidepressant effect].