Establishing Stable Cannabinoid and Opioid Receptor Cell Lines

Chinese hamster ovary (CHO-K1) cells were stably transfected with the human cannabinoid subtype 2 receptor (CNR2; hCB2) [28 (link)] or the human mu-opiod receptor (MOR, CHO-hMOR) [29 (link)]. CHO cells stably expressing hCB1 receptors (CNR1; CHO-hCB1) were purchased from DiscoverRx Corporation (Fremont, CA). CHO-hCB2 and CHO-hMOR cell lines were cultured in DMEM (Mediatech Inc., Manassas, VA) while CHO-hCB1 cells were cultured in HAM’s F-12 K media (ATCC, Manssas, VA). Media for all cell types contained 10% fetal calf serum (Gemini Bioproducts, Sacramento, CA), 0.05 IU/mL penicillin, 50 μg/mL streptomycin (Invitrogen, Carlsbad, CA), and 250 μg/mL of Geneticin (or G418; Sigma-Aldrich, St. Louis, MO). All cell types were maintained in a humidified chamber at 37°C with 5% CO₂, harvested when flasks reached approximately 80% confluency, and only cells from passages 1–15 were used in all experiments.