Figure 7
Three cohorts of rats underwent right distal tibial fracture and hindlimb cast immobilization for four weeks. After baseline testing, rats were divided into 4 groups. One fracture (FX) group had no other treatment (FX, n = 16), another fracture group underwent daily intraperitoneal (i.p.) injections with the NK1 receptor antagonist LY303870 (20 mg/kg i.p., FX + LY303870 i.p., n = 15) over an 8-day interval prior to cast removal, and another fracture group underwent a single intraplantar (i.p.l) injection of LY303870 (50 μg) on the day after cast removal and 1 h prior to testing (FX + LY303870 i.p.l. 1 h, n = 8). At four weeks post-fracture the 8 days of systemic LY303870 treatment reduced hindpaw mechanical allodynia (A), unweighting (B), warmth (C) and edema (D) that developed after fracture. In addition, all four tests were carried out 1 h after the intraplantar injection of LY303870. A single intraplantar injection of LY303870 also reduced allodynia and unweighting, but had no effect on warmth or edema. Measurements for (A), (C), and (D) represent the difference between the fracture side and the contralateral paw, thus a positive value represents an increase in temperature or thickness on the fracture side; a negative value represents a decrease in mechanical nociceptive thresholds on the affected side. Measurements for (B) represent weight-bearing on the fracture hindlimb as a ratio to 50% of bilateral hindlimb loading, thus a percentage lower than 100% represents hindpaw unweighting. Data were analyzed using one-way analysis of variance (ANOVA) followed by Neuman-Keuls multiple comparison test. *P < 0.05, **P < 0.01, ***P < 0.001 fracture vs. control (n = 13) values, and ## P < 0.01 and ### P < 0.001 for fracture with LY303870 treatments vs. fracture with vehicle treatment.