Role of extracellular signal-regulated kinase in central amygdala on fentanyl-induced hyperalgesia in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the role of extracellular signal-regulated kinase1/2 (ERK1/2) in the central amygdala on fentanyl-induced hyperalgesia in rats.Methods Thirty-two male SpragueDawley rats, weighing 60-100 g, were randomly divided into 4 groups (n =8 each) using a random number table control group (group C), fentanyl-induced hyperalgesia group (group H), U0124 group (group U1) , and U0126 group (group U2).A catheter was implanted in the central amygdale.In group C, normal saline was injected subcutaneously, and 6.5 h later dimethyl sulfoxide (DMSO) was injected via the catheter.In group H, fentanyl was injected subcutaneously to induce hyperalgesia, and 6.5 h later DMSO was injected via the catheter.In group U1, hyperalgesia was induced, and 6.5 h later ERK1 inhibitor U0124 1.5 nmol was injected via the catheter.In group U2, hyperalgesia was induced, and 6.5 h later ERK1/2 inhibitor U0126 1.5 nmol was injected via the catheter.Mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal threshold (TWT) were measured before fentanyl injection, at 6.5 h after injection, and at 30 min after DMSO or U0124/U0126 administration via the catheter (T0-2).After the last measurement of pain threshold, the rats were sacrificed, and the amygdala tissues were sampled for detection of the expression of phosphorylated ERK1/2 (p-ERK1/2) by Western blot in groups C and H.Results Compared with group C, the MWT and TWT were significantly decreased at T1,2in H and U1 groups, and at T1in group U2 (P＜0.05) , the expression of p-ERK2 was up-regulated (P＜0.05) , and no significant change was found in the expression of p-ERK1 in group H (P＞0.05).Compared with group H,the MWT and TWT were significantly increased at T2 in group U2 (P＜0.05) , and no significant change was found in MWT, TWT in group U1 (P＞0.05).Conclusion ERK2 activation in the central amygdala is involved in the development of fentanyl-induced hyperalgesia in rats.