Phosphorylation of ERK1/2 in the DH of spinal cord (L4-L5) after saline or EP pretreatment. (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 number enhancement of p-ERK-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 p-ERK-IR cells in spinal DH following EP preinjection. The enhancement in the number of p-ERK positive cells produced by formalin was significantly decreased in spinal DH by EP pre-administration. The mean number of p-ERK positive 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).