The cell types that express HMGB1, TLR4, and RAGE in the rats spinal dorsal horn following repeated intrathecal (i.t.) injections of morphine. (a-c) Representative images showing that HMGB1 colocalized with the spinal neuronal marker NeuN (a), the astrocytic marker GFAP (b), and the microglial marker OX42 (c). (d-f) Representative images showing TLR4 colocalization with NeuN (d), GFAP (e), and OX42 (f). (g-i) Representative images showing RAGE colocalization with NeuN (g) and GFAP (h) but not with OX42 (i). Images in a-i, scale bar = 50 μm.