Effects of yohimbine, ketanserin, and prazosin on the antinociception of ginsenoside Rf. Ginsenoside Rf (1.5 mg/kg) was intraperitoneally administered 2 h after plantar incision (AP). Yohimbine, prazosin, and ketanserin were administered 10 min before the injection of ginsenoside Rf. The mechanical withdrawal threshold was measured at predetermined time points. The natural log transformation of the mechanical withdrawal threshold was plotted on the vertical axis. BI: 1 d before plantar incision. AP: 2 h after plantar incision. Rf 1.5 group : 1.5 mg/kg injection of ginsenoside Rf. Yohimbine group: 2 mg/kg injection of yohimbine. Ketanserin group: 1 mg/kg injection of ketanserin. Prazosin group: 1 mg/kg injection of prazosin. 15–120 m: 15–120 min after injection of ginsenoside Rf. 24–48 h: 24–48 h after injection of ginsenoside Rf. BI, before incision; PI, plantar incision.