Cranial irradiation increased astrocytic co-labeling of complement C3 in the hippocampus. Representative z stacks from laser scanning confocal microscopy (green, GFAP; red, C3, panel A) and volumetric quantification of 3D rendered GFAP+ astrocytes (green, panel B) showed a significantly elevated total C3 and GFAP co-labeling with C3 (magenta spots, panel B) one month after either 10 Gy CONV-RT or FLASH-RT (panel C). Data are presented as mean ± SEM (n = 6 animals per group). P values are derived from non-parametric Kruskal-Wallis H test and Mann-Whitney’s comparison between each group as indicated. Scale bar = 10 μm (panel A and B).