Fig. 4. Analgesic effect of systemic multiple phenyl N -tert-butylnitrone (PBN) administrations on established paclitaxel (PAC)-induced neuropathic pain in rats. Paclitaxel (2 mg/kg) was injected intraperitoneally on four alternate days (days 0, 2, 4, and 6, down arrows ) in 11 rats, and subsequently, the thresholds were significantly reduced. PBN (100 mg/kg) was injected intraperitoneally twice daily at 12 h interval for 3 days beginning on day 35. The control group received an intraperitoneal (ip) injection of saline. Mechanical thresholds were measured once a day before injection of PBN. Repeated injection of PBN significantly increased mechanical threshold the next day (day 36) and maintained it for 4 days. Data are expressed as means ± SEMs. Asterisks  indicate significant differences from the saline control group by a two-way repeated measures analysis of variance, followed by the Tukey post hoc  test.