Background

In the mammalian central nervous system (CNS), γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter [1]. GABA (A) receptors are ionotropic receptors that, upon GABA binding, open chloride (Cl^-) channels, leading to neuronal hyperpolarization and inhibition [2]. These receptors are pentameric ligand-gated ion channels, typically assembled from five subunits selected from 19 known types: α1–6, β1–3, γ1–3, δ, ε, θ, π, and ρ1–3 [3]. The most common brain configuration consists of two α, two β, and one additional subunit, forming αβγ or αβδ combinations, which correspond to synaptic and extrasynaptic receptors, respectively [4]. The specific subunit composition determines each receptor's pharmacological profile, regional brain distribution, and physiological role. Among the subunits, α5 is particularly notable for its involvement in cognitive processes, including learning and spatial memory [5–7]. The α5β2γ2 GABA (A) receptor subtype has been identified as a key modulator of cognition and anxiety-related behaviors. This receptor subtype is highly expressed in the hippocampus, particularly in the CA1 and CA3 regions, areas critical for memory encoding and spatial navigation [8,9]. Its anatomical localization and functional role make α5β2γ2 a compelling target for cognitive modulation. In this context, natural compounds with neuroactive properties may offer new avenues for modulating GABAergic signaling.

Mitragyna speciosa (commonly known as Kratom) is a tropical medicinal plant traditionally used for its stimulant and opioid-like effects [10]. Among its constituents, mitragynine is the primary and pharmacologically active alkaloid. Mitragynine exhibits analgesic, anti-inflammatory, and psychoactive properties [11], primarily acting as a partial agonist at the μ-opioid receptor and an antagonist at κ- and δ-opioid receptors [12]. Beyond its opioid-related activity, mitragynine has shown potential to interact with receptors involved in cognitive processes, raising interest in its neuromodulatory effects on GABAergic systems [13]. To systematically explore this potential, we developed an integrated in silico workflow to investigate the interaction of mitragynine with the α5β2γ2 GABA (A) receptor subtype. The protocol begins with homology modeling of the receptor using the α1β2γ2 subtype as a structural template. Following model optimization and validation, molecular docking is performed to predict mitragynine’s binding affinity and identify key interaction sites. Finally, molecular dynamics (MD) simulations are used to assess the stability and conformational behavior of the receptor–ligand complex. Overall, this computational approach provides detailed structural and dynamic insights into the potential neuromodulatory action of mitragynine on a cognitively significant GABA (A) receptor subtype.