Planarians (Dugesia dorotocephala) were purchased from Carolina Biological Supply (Burlington, NC, USA). (−)-Cocaine hydrochloride was provided by NIDA (Bethesda, MD, USA). Clorazepate dipotassium salt was purchased from Sigma-Aldrich (St. Louis MO, USA). Drugs were dissolved in spring water. Concentrations were based on prior work (Tallarida et al., 2014 (link)).