A. Immunoblotting analysis of Iba1 protein in the spinal cord of morphine (Mor)-treated WT (C57BL/6) mice (i.p. daily for first 4 days) at day 7 indicated in bottom paradigm (**, p<0.01). B. Immunoblotting analysis of Iba1 protein in the spinal cord of CD11b-DTR transgenic mice at day 7, treated by vehicle (Veh), morphine (Mor) or Mor+DT (diphtheria toxin) ( **, p <0.01). DT was injected (i.t.) daily at the first two days and morphine administration is similar to Fig.1A to evaluate the role of microglia in OIH expression. C. Immunofluorescent images of microglia in the spinal cord dorsal horn of the CD11b-DTR transgenic mice at day 7, treated by vehicle (Veh), DT, Mor) or Mor+DT.