Fig. 6

Reduced formalin-induced neuronal activity in the absence of microglia in the spinal cord. a, b Intraplantar injection of formalin induced c-fos expression and pERK activation co-localized with NeuN immunostaining. a Representative images showing double staining of c-fos⁺ or pERK⁺ (red) and NeuN⁺ (green) cells in the spinal cord DH either 2 h after formalin injection (c-fos staining) or 40 min after formalin injection (pERK staining). Scale bar, 100 mm. b Quantification of the percentage of c-fos⁺NeuN⁺ or pERK⁺NeuN⁺ cells among all c-fos⁺ or pERK⁺ cells. n = 4 mice/group. c, e Representative images of c-fos -positive (c) and pERK -positive (e) cells in ipsilateral dorsal horn from the sham, control (CTRL) and microglia ablation (MG Abl) POD3 mice. Scale bar, 200 μm. d, f Quantitative data showing the number of c-fos⁺ cells 2 h after intraplantar formalin injection (d) or pERK⁺ cells 40 min after intraplantar formalin injection (f) in the ipsilateral dorsal horn of WT sham, WT control and microglia ablation POD3 mice. Data are presented as mean ± SEM; ***P < 0.001, compared with control, unpaired 2-tailed Student’s t test, n = 5–8 mice/group