Effects of different time point intervention of TEAS on phosphorylation of spinal ERK1/2 and inflammatory pain

Objective:To observe the analgesic effects of transcutaneous electrical acupoint stimulation(TEAS),which administrated at different time,and its intervention on the activation of ERK1/2 in spinal cord dorsal horn.Methods:All rats were randomly divided into normal group(n group),model group(CFA group),TEAS group and pre-TEAS group.Inflammatory pain was induced by injecting subcutaneously with 100μL Complete Freund's Adjuvant(CFA) into right hindpaw of rats in CFA,TEAS and pre-TEAS group.Pre-TEAS and TEAS groups were respectively applied to bilateral 'Zusanli'(ST36) and 'Kunlun'(BL60) at 7d before CFA-treated and 5.5h after CFA injection.The paw withdrawal thresholds(PWTs) were measured by using Dynamic Plantar Aesthesiometer 37 450 on 7d before CFA-treated(as BASE) and at 5h,6h after CFA injection.The expression level of ERK1/2 in spinal cord dorsal horn(SCDH) was detected by Western Blot at 5h and 6h after CFA injection.Results:Compared with that of n group,PWTs of rats in CFA group were decreased markedly during the whole experiment,and the expression level of p-ERK1/2 of ipsilateral SCDH was increased(P0.01).PWTs in TEAS group were higher obviously than those in CFA group at 6h after CFA injection(P0.01).Moreover,the expression level of p-ERK1/2 of ipsilateral SCDH was significantly less than those in CFA group at the same time point(P0.01).Although PWTs in pre-TEAS group were higher obviously than those in CFA and TEAS groups at 5h after CFA injection(P0.01),there was no significant difference among three groups in p-ERK1/2 expression.In addition,there were also no significant difference between TEAS and pre-TEAS groups both in PWTs and the expression level of activated ERK1/2 at 6h after CFA injection.Conclusion:Inhibition phosphorylation of ERK1/2 in SCDH of CFA rats maybe a new mechanism of TEAS analgesia.However,the underlying mechanism of pre-TEAS analgesia still need more studies.