The expression of phosphorylated CREB (pCREB) in the dorsal horn is attenuated in BLT1KO mice. Representative diaminobenzidine-stained images showing pCREB-positive neurons in sections of the ipsilateral (A) and contralateral (B) dorsal horn of the lumbar spinal cord before or 20 min after a peripheral formalin injection (magnification, 100×). Arrowheads indicate pCREB-positive neurons. The number of pCREB-positive neurons in the ipsilateral (C) and contralateral (D) dorsal horn of the lumbar spinal cord prior to or 20 min after formalin injections. (**** p < 0.0001 vs. BLT1WT mice, n = 6, two-way ANOVA with Bonferroni post hoc test).