Iba1-immunostaining in LEW, FIS and WIS rats subjected to nerve injury. The photomicrographs show the effect of a chronic constriction injury (CCI) of the right sciatic nerve on microglial cell activation in the dorsal horn of the spinal cord segment L4 on day 21 after surgery in Lewis (LEW; Top), Fischer (FIS; Middle) and Wistar (WIS; Bottom) rats. The number and staining density of Iba1-immunopositive microglial cells was clearly enhanced in the right dorsal horn (side of CCI) compared to the left unaffected side in all three strains. Differences between strains were not obvious. Scale bars: 100 μm.