Roles of phosphorylated extracellular signal-regulated kinase in rats with incisional hyperalgesia / 中华神经医学杂志

ABSTRACT

Objective To investigate the changes of phosphorylated extracellular signal-regulated kinase (p-ERK) expression in the immunoreactive cells of the spinal dorsal hom after plantar incision,and explore the effects of intrathecal administration of MEK inhibitor U0126 on physiological pain threshold in rat models with incisional pain.Methods Thirty-two male SD rats were equally randomized into control group (C group),incisional pain group (I group),intrathecal U0126 group (Ugroup) and intrathecal DMSO group (D group).Twenty-μL physiological saline was injected into the rats of the C group and I group,respectively.Ten-μL DMSO and U0126 were injected into the rats in the U group and D group,respectively.Rat models with incisionai pain were induced in the other 3 groups except the C group.Mechanical hyperalgesia were evaluated by paw-pressure before and 2,24 h and 2 d after the inducement.Another 24 rats were treated as the above method and equally divided into 4 groups; the numbers of p-ERK immunoreactive cells in the dorsal horn were quantified to determine the ERK activation 2 and 24 after the model inducement.Results The paw-pressure threshold in I group and D group 2 and 24 h,and 2 d after the incision,and that in U group 2 and 24 h after the incision were significantly decreased as compared with that in C group (P<0.05); that between I group and D group showed no significant difference (P>0.05); that in the U group was obviously higher than that in the I group and D group at the same time points (P<0.05).Significantly increased numbers of p-ERK immunoreactive cells in the I group and D group were observed as compared with those in the C group (P<0.05); those in the U group was obviously decreased as compared with those in the I group and D group at the same time points (P<0.05).Conclusion Plantar incision-induced mechanical hyperalgesia can be prevented by intrathecal injection of U0126 through decreasing the expression of p-ERK positive cells,indicating that ERK pathway in the spinal dorsal horn involves in the incision-induced mechanical hyperalgesia in rats.