Chemical agent preparation

OPs Chlorpyrifos (CPF), Malathion (MT), and Parathion (PT) were purchased from Sigma-Aldrich (St. Louis, MO, USA) in neat form. They were dissolved in Dimethyl sulfoxide (DMSO) first, and then diluted to final concentration of 5% DMSO in Dulbecco’s modified eagle’s medium (DMEM, ATCC, Manassas, VA, USA) and then further diluted in DMEM to concentrations of 10⁻¹, 10⁻³, 10⁻⁵, and 10⁻⁷ M. Muscimol (MUS, Sigma-Aldrich, St. Louis, MO, USA) and Dextromethorphan (DXM, USP™, Rockville, MD, USA) were diluted in DMEM to concentrations of 10⁻¹, 10⁻², 10⁻³, and 10⁻⁴ mM. Pure Ethanol (EtOH) purchased from Sigma-Aldrich (St. Louis, MO, USA) was diluted in DMEM to concentrations of 500, 100, 20, and 5 mM. The DMSO-contained medium were used as control (CON): 5% DMSO in DMEM for OPs, DMEM for MUS, DXM and EtOH.