Fig. 2. The time courses of mechanical threshold in paclitaxel (PAC)-induced neuropathic pain in rats. PAC (2 mg/kg) was injected intraperitoneally on four alternate days (days 0, 2, 4, and 6; cumulated doses of 8 mg/kg, downward arrows ) in rats. The vehicle group received equal volume (1 ml/kg) of 4% dimethyl sulfoxide and 4% Tween 80 in saline. Phenyl N -tert-butylnitrone (PBN) (100 mg/kg) was injected intraperitoneally twice a day for 3 days beginning on day 0 in normal rats. Note that PAC significantly decreased mechanical thresholds compared with the vehicle group. PBN or vehicle group did not increase mechanical threshold when given to normal animals. Data are expressed as means ± SEMs. Asterisks  indicate values significantly different (P < 0.05) from corresponding vehicle values by using a two-way repeated measures analysis of variance with a repeated time factor, followed by Tukey post hoc  test.