The hippocampus of C5aRKO mice show decreased GluR2 expression in vivo in response to KA when compared to WT littermates. KA or vehicle (Veh) was administered intraventricularly in C5aRKO mice and age matched wild type litermates (WT) (n = 4). Frozen hippocampal brain sections from these mice were then probed immunocytochemically for GluR2 expression using GluR2 antibody. GluR2 immunoreactivity was quantitated from 8–10 randomly selected fields and results were expressed as a percent of vehicle treated WT controls. KA significantly decreased the expression of GluR2 immunoreactivity in the mossy fiber region of C5aRKO mice (Fig. A, B). The arrow points towards the region in the inset which shows the GluR2 immunoreactivity in the mossy fibers of the CA3 region. Hippocampal GluR2 immunoreactivity was reduced in C5aRKO mice treated with KA compared to C5aRKO mice treated with vehicle. All results are expressed as mean ± SD. Difference between groups was assessed by t-test, *p < 0.05. SO = stratum oriens; SR = stratum radiatum; SLM = stratum lacunosum moleculare.