Effects of 2-BFI or phenyzoline alone and in combination with acetaminophen on CFA-induced mechanical hyperalgesia, thermal hyperalgesia, and responding rate. Top, left: isobologram for 2-BFI/acetaminophen mixture for mechanical hyperalgesia; Top, middle: isobologram for 2-BFI/acetaminophen mixture for thermal hyperalgesia; Top, right: isobologram for 2-BFI/acetaminophen mixture for responding rate. Ordinate, ED50 value (95% CL) of 2-BFI (mg/kg); Abscissa, ED50 value (95% CL) of acetaminophen (mg/kg). Bottom, left: isobologram for phenyzoline/acetaminophen mixture for mechanical hyperalgesia; Bottom, middle: isobologram for phenyzoline/acetaminophen mixture for thermal hyperalgesia; Bottom, right: isobologram for phenyzoline/acetaminophen mixture for responding rate. Ordinate, ED50 value (95% CL) of phenyzoline (mg/kg); Abscissa, ED50 value (95% CL) of acetaminophen (mg/kg).