Simulating dynamic interaction between diazepam and ethanol targeting the GABA_A receptor via in silico model

Combined diazepam-ethanol poisoning is common in forensic toxicology. Both diazepam and ethanol can inhibit the central nervous system via the γ-aminobutyric acid (GABA) ligand gated chloride ion channel, GABA_A Receptor (GABA_AR). As the common target of diazepam and ethanol, whether GABA_AR is the key target of their combined action remains unclear. This study aimed to explore their interaction based on the synergistic mechanisms between diazepam and ethanol targeting the GABA_AR. Four models were built in silico based on the crystal structure of GABA_AR. Molecular dynamic processes of the four models were simulated by the GPU-accelerated pmemd.cuda program in the Amber18 package. Results showed that ethanol inclined to combine the adjacent GABA or diazepam sites, minimized fluctuations of the root-mean-square deviation (RMSD) in the molecular dynamic process of GABA or diazepam binding the GABA_AR, and increased the release of binding energy of GABA or diazepam binding the GABA_AR. Results also showed that diazepam had less effect on the RMSD fluctuation or the binding energy release of GABA binding GABA_AR. The formation of complex of diazepam and GABA_AR could minimize the RMSD fluctuation and increase binding energy release of ethanol binding GABA_AR. Thus, ethanol, bridging GABA and diazepam, could strengthen the complex of GABA binding the GABA_AR, as well as the complex of diazepam binding the GABA_AR. However, whether diazepam binds GABA_AR or not, it cannot affect GABA binding the GABA_AR; and yet the complex of diazepam and GABA_AR can stabilize the complex of ethanol and GABA_AR.