Representative photomicrographs and graph showing immunoreactivity of c-Fos in the spinal DH (L4-5) following formalin injection. (A) Western blots from spinal DH. N, normal. FA, saline-pretreated and formalin-treated rats, FA + EP, EP-pretreated and formalin-treated rats. E, EP alone. (B-D) Photomicrographs showing c-Fos expression in the spinal DH from normal rats (B), saline-pretreated and formalin-treated rats (C), EP-pretreated and formalin-treated rats (D). The elevated number of c-Fos-immunorective (IR) cells produced by formalin was clearly decreased in both the superficial lamina (I-II) and deep lamina (III-IV) by EP-pretreatment. Insets are high magnification of the open rectangles. Scale bar = 100 μm. (E) The number of c-Fos-IR cells in spinal DH following EP pre-injection. The mean number of c-Fos-IR cells was calculated by averaging the total numbers per each region. Values are expressed as mean ± SEM. +P < 0.01 vs. normal rats (saline-pretreated and saline-treated); *P < 0.01 vs. control rats (saline-pretreated and formalin-treated).