Fig. 4
From: Spinal microglia contribute to sustained inflammatory pain via amplifying neuronal activity
Microglial process dynamics are enhanced during formalin induced phase-II persistent inflammatory pain. a Representative in vivo z-stack images of L4-5 ipsilateral spinal microglia from time-lapse imaging taken before (− 10 min, BL) and 20 (F20), 40 (F40), or 60 min (F60) after either intraplantar formalin injection (5% in PBS, 10 μl) or control injection (PBS). Higher magnification images from boxed regions of BL in red and F40 in green were merged in BL/F40 to show microglial process extension. Time lapse two-photon z-stack images were also taken from control mice at before (–10 min, BL) and 20 min (C20), 40 min (C40), 60 min (C60) after intraplantar saline injection. Higher magnification images from boxed regions of BL in red and C40 in green were merged in BL/C40. Note that there was no dramatic change in microglial process extension in control conditions. Scale bars represent 40 μm and 20 μm. b Quantitative data showing dynamics of spinal microglial processes, represented as normalized motility index, in control and formalin-treated groups. Data are shown as mean ± SEM. ***P < 0.001, compared to control. Two-way ANOVA. n = 5–6 mice/group (Control: n = 6, Formalin: n = 5). c Quantitative data showing average motility index of spinal microglial processes in control and formalin-treated group within different time windows (− 10 ~ 0 min before and 11 ~ 40 min after saline/formalin injection). Data are shown as mean ± SEM. **P < 0.01, compared to control. Unpaired 2-tailed Student’s t test. n = 6 for control and n = 5 for formalin-treated group. d Quantitative data showing spinal microglial process length, represented as normalized process length, in control and formalin-treated groups at different time points with respect to saline/formalin injection. Process lengths were analyzed every 10 min. Data are shown as mean ± SEM. *P < 0.05, **P < 0.01, compared to control. Unpaired 2-tailed Student’s t test. n = 6–7/group. e Sholl analysis plot representing microglia complexity in control and formalin-treated group. n = 7–13/group