Morphine administration increased spinal Toll-like receptor 4 (TLR4) but not brain-derived neurotrophic factor (BDNF) nor prodynorphin (PDYN) expression in fracture/pin (FX) mice at 2 weeks post injury. Levels of BDNF (A and B), PDYN (C and D), and TLR4 (E and F) mRNA and protein were detected using quantitative polymerase chain reaction and enzyme-linked immunosorbent assays. There were no significant differences in expression levels for either BDNF or PDYN gene between any of the groups. However, increased levels of TLR4 mRNA and protein expression were observed in vehicle-treated FX mice, and morphine treatment further dramatically enhanced this upregulation. Data were analyzed using a one-way ANOVA with Bonferroni correction test for post hoc contrasts. Data are expressed as mean values ± SD, N = 6 per cohort in (A–D), and N = 10 per cohort in (E and F). *P < 0.05, ***P < 0.01 FX + Vehicle or FX + Morphine versus Sham + Vehicle, ##P < 0.01, ###P < 0.001 FX + Morphine versus FX + Vehicle.