The Role Of ERK1/2Phosphorylation Within Trigrminal Nucleus Caudalis In Chronic Migraine Rat

ObjectiveMigraine is a common and disabling problem, with a prevalence of7~11%of the general population worldwide. The pathogenesis of migraineremains unclear. In this study, we investigated the expression level ofextracellular signal-regulated kinase1/2(ERK1/2) phosphorylation in thetrigeminal nucleus caudali (TNC) following inflammatory stimulation tothe dura matter. We also observed the influence of MEK1inhibitorPD98059on pain threshold and the expression level of calcitoningene-related peptide (CGRP) in trigeminal nucleus caudalis, to explore thepotential role of ERK1/2phosphorylation in chronic migraine (CM) modelrat.Materials and Methods1. Experiments were performed on male Sprague-Dawley rats(n＝80).They were randomly divided into five groups: Control group (n＝16),Sham group (n＝16, stimulation of the dura mater with0.01M PBS), CM group (n＝16, inflammatory stimulation of the dura mater withinflammatory soup), PD98059group (n＝16, CM rats withintracerebroventricular injection of ΜEK1inhibitor PD98059) and NSgroup (n＝16, CM rats with intracerebroventricular injection of saline).2. Neurobehavioral changes were observed and paw withdrawalmechanical threshold (PWMT) was tested by electric Von Frey.3. Western blot analysis and immunofluorescence staining were usedto detect the expression of ERK1/2, pERK1/2and CGRP in trigeminalnucleus caudalis.Result1. The frequency of head-scratching, hair-licking and cage-climbingand neurobehavioral scores were much higher in CM group, compared withControl group and Sham group (p<0.05). Paw withdrawal mechanicalthresholds were significantly lower (p<0.05). Neurobehavioral scores andPWMTs significantly improved after intracerebroventricular injection ofPD98059(p<0.05).2. Western blot and immunofluorescence staining were employed todetect the expression of ERK1/2and pERK1/2in rat trigeminal nucleuscaudalis. The results showed that the expression of pERK1/2was muchhigher in CM group than Control group and Sham group (p<0.05). Therewas no significant difference of ERK1/2expression between groups.Intracerebroventricular injection of MEK1inhibitor PD98059could inhibit the expression of pERK1/2(p<0.05), rather than ERK1/2in trigeminalnucleus caudalis.3. Western blot and immunofluorescence staining were used to detectthe expression of CGRP in rat trigeminal nucleus caudalis. The resultsshowed that compared with Control group and Sham group, CGRPexpression was increased in CM group (p<0.05). Intracerebroventricularinjection of MEK1inhibitor PD98059could significantly inhibit theexpression of CGRP (p<0.05).Conclusion1. Dural stimulation by inflammatory soup can effectively build the ratmodel of chronic migraine.2. The expression of pERK1/2increased in trigeminal nucleuscaudalis of chronic migraine rat. Inflammatory stimulation of the duramater increased the level of ERK1/2phosphorylation in trigeminal nucleuscaudalis. The phosphorylation of ERK1/2might play a role in thedevelopment of chronic migraine.3. Intracerebroventricular injection of MEK1inhibitor PD98059canreduce pain.4. Intracerebroventricular injection of MEK1inhibitor PD98059candecrease the expression of CGRP in trigeminal nucleus caudalis.Extracellular signal-regulated kinase1/2may be involved in chronicmigraine by meditating calcitonin gene-related peptide.