MAPKs are a family of important intracellular signaling molecules that transduce extracellular stimuli into intracellular responses in a wide variety of circumstances and controls cell function and survival.Three subfamilies of MAPKs have been identified in mammals:ERK,JNK,and p38 MAPK.Accumulating evidences demonstrated that p38 was involved in pain hypersentivity and pain facilitation and the activation of p38 in the spinal cord had been seen primarily in microglia.Here we tested the hypothesis that group Ⅰ mGluRs were involved into the activation of p38 MAPK induced by formalin injection.Experiments were performed on male Sprague-Dawley rats weighing 120±g.We observed the level of phosphorylated p38 (P-p38) expression in normal condition and the levels of expression of P-p38 at different time point,5,15,60 min,1,3,7,14,28 d after formalin injection assessed by western blotting.Results showed that if the baseline level of P-p38 was thought as 100%,the data of each time point was 303.78% (P < 0.05),182.56%,101.68%,273.84% (P < 0.05),101.22%,174.78%,104.08%,108.97%,respectively.