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. 2019 Jul 10;13:306. doi: 10.3389/fncel.2019.00306

FIGURE 1.

FIGURE 1

Peripheral inflammation induces astrocyte reactivity in the spinal cord. (A) Experimental design for the CFA (complete Freund’s adjuvant) model of peripheral inflammatory pain. One hour after the basal mechanical nociception, CFA or saline (Sal) were injected into the right hind paw of rats. Two, 7 or 14 days later, the second (2nd) mechanical nociception and histology were performed. (B,C) Mechanical nociception of the ipsilateral (B) and contralateral (C) hind paws was quantified before (day 0) and after saline or CFA injection (days 2, 7 and 14; n = 6/group). (D) Bottom: scheme showing the entry zone of the sciatic nerve in the lumbar spinal cord between L3 and L5 used for histology (∼ 2 mm). Top: GFAP-labeled astrocytes in a transverse section of the lumbar spinal cord (D = dorsal, V = ventral coordinates relative to the central canal). The ipsilateral and contralateral sides are relative to the paw injection. The gray matter is within the white line. The gray square represents the area of the dorsal horn acquired in the histology studies. (E) Representative fluorescent images and (F) quantification of GFAP-labeled astrocytes in the dorsal horn of the lumbar spinal cord, showing the saline and CFA groups in 2, 7, or 14 days after the paw injection. All images are from the ipsilateral side. The dashed and blue lines delimit the Rexed’s laminae and the region of interest (Savoie et al., 2019) used for the fluorescence intensity quantification, respectively. All values are relative to each respective saline group (n = 3 for saline and n = 4 for CFA groups, six slices per animal). (G) Representative fluorescent images of GFAP-labeled astrocytes in the dorsal horn of the spinal cord, showing the contralateral (left) and ipsilateral (right) sides of the Saline (Stevens et al., 2007) and CFA (bottom) groups. (H) Left: Intragroup analysis of GFAP fluorescence intensity of the ipsilateral relative to the contralateral side in each group (saline in blue, CFA in red). Right: Intergroup analysis of GFAP fluorescence intensity of the contralateral and ipsilateral sides of CFA-treated relative to the saline-injected rats (contralateral in purple, ipsilateral in gray; n = 4, six slices per animal; #p < 0.05; ##p < 0.01; ####p < 0.0001). In all figures, the scale bars represent 100 μm, except in figure (D) (200 μm). Summary data are represented as mean ± SEM. In figures (B,C,F), ∗∗∗∗p < 0.0001.