Drugs were added to the superfusate in known concentrations. U69593 and nor-binaltorphimine (norBNI) were purchased from Santa Cruz Biotechnology (Santa Cruz, CA) and dissolved in dimethylsulfoxide. Dimethylsulfoxide final concentration was 0.05–0.1%, which did not affect the studied synaptic responses in control experiments. Dynorphin A [1–17], CTAP and bicuculline were purchased from Tocris (Ellisville, MO), and ethanol from Remet (La Mirada, CA). We purchased all other chemicals from Sigma-Aldrich (St Louis, MO).
