Electrophysiological and molecular docking analysis of 1,8-Cineole's effects on potassium currents in mouse DRG neurons

Abstract

1,8-cineole (CIN) is a monoterpene widely used in traditional medicine, as it promotes biological and pharmacological effects, including the inhibition of neuronal excitability. This inhibition might be due to ion channel blockade, as reported for voltage-dependent Na⁺ and Ca²⁺ channels. However, voltage-dependent K⁺ channels (K_v) are also relevant proteins in neuronal excitability. Thus, this study investigated the effects of CIN on potassium current (I_K+) in dissociated neurons from mouse dorsal root ganglia (DRG) using electrophysiological and molecular docking approaches. The whole-cell patch-clamp technique recorded I_K+ in voltage-clamp mode. Other experiments recorded action potentials (APs) in the current-clamp mode, and molecular docking used specific software (AutoDock Vina, LigPlot⁺, PyMol). Consequently, CIN achieved a partial concentration-dependent inhibition of I_K+. CIN at 3.0 and 6.0 mM showed similar blockade values of ∼50 % of peak and sustained I_K+. IV plots from cells exposed to 3.0 mM CIN shifted by ∼15 mV toward negative values in the G/G_max curve of sustained I_K+. Peak I_K + had no significant shift. Molecular docking simulations demonstrated that CIN interacts with the binding pockets of K_v2.1 and K_v3.4 channels with ΔG values of −4.7 kcal.mol⁻¹ and −2.0 kcal.mol⁻¹ interaction energy, respectively. This study also investigated 3 mM CIN effects on neuronal excitability. CIN blocked APs in two of eight neurons and altered several electrophysiological parameters related to excitability in the remaining six neurons. These parameters included AP amplitude, AP maximum rise slope, and AP time-to-peak without changes in resting membrane potential. This study concluded that CIN blocks total I_K+ and interacts with K⁺ channels. Also, the changes in neuronal excitability might be due to CIN effects on K⁺ channels, working through a mechanism independent of resting membrane potential.