Fig. 1

Intraspinal injection of rAQP4 IgG induces mechanical allodynia. A Schema of experimental procedures. B Representative images of GFAP, AQP4, and DAPI staining in the spinal cords of rats 3 days after receiving rAQP4 IgG or control IgG. Scale bar = 200 μm. C High magnification images of the injury site in rAQP4 IgG–treated group. Astrogliosis is observed in peripheral lesion of the injury site. Scale bar = 100μm. D GFAP, AQP4, and DAPI staining at the injection site of the spinal cord in rAQP4 IgG–treated group 5 days after the injection. Scale bar = 200 μm. E Time course of thresholds of mechanical allodynia. Thresholds of mechanical allodynia assessed 0 (pre-injection), 1, 3, 5, 7, 10, 14, 21, and 28 days after intraspinal injection of either rAQP4 IgG (n = 6) or control IgG (n = 6). Data are expressed as means ± SEM and were analyzed by factorial repeated measures ANOVA with three between-subjects factors [group: rAQP4 and control; day 1, 3, 5, 7, 10, 14, 21, and 28; RL: right (Rt) and left (Lt)] and one within-subjects factor [the same rat’s paired Rt and Lt data]. The main effect of group (P = 0.018) and the interactions of group times day (P < 0.001) and group times RL (P = 0.045) were statistically significant. For the visualization, the asterisks indicate two-group comparison at each day. F Thresholds of mechanical allodynia assessed 3 days after intraspinal injection of either undiluted rAQP4 (n = 5), 1/10 dose rAQP4 IgG (n = 4), 1/100 dose rAQP4 IgG (n = 4), or 1/1000 dose rAQP4 IgG (n = 4). Data are expressed as means ± SEM and analyzed by two-way repeated measures ANOVA with one within-subjects factor [the same rat’s paired right (Rt) and left (Lt) data]. ***P < 0.001, **P < 0.01, *P < 0.05. N.S., not significant