(A, B) QH1-immunolabeled (green) whole-mounted retina explants from a quail embryo at 6.5 days of incubation cultured for 24 hours in vitro (E6.5+24hiv) in suramin-free (CONTROL, A) or 100 μM suramin-containing (SURAMIN, B) medium. Abundant QH1-positive microglial cells have entered the retina from the base of the pecten (BP, delimited with a dashed line) in the non-treated control explant (A), whereas very scarce microglial cells are seen in the suramin-treated explant (B). Scale bar: 100 μm (C). Number of microglial cells migrating within the retina is significantly lower in suramin-treated E6.5+24hiv retina explants (Suramin, red bar) than in non-treated controls (CTRL, blue bar). Data are expressed as means ± SEM (n = 15). Asterisk depicts significant differences (*P<0.05, Student´s t-test).