Effect of suramin on neurosphere size and on the number of viable neural progenitor cells. Neural progenitor cells (NPCs) of the postnatal rat subventricular zone were cultured in the absence (control) or presence of the purinergic receptor blocker suramin. The diameter of the formed neurospheres, as well as the number of viable cells after neurosphere disaggregation, was measured 72 h after seeding. (A,B) Phase-contrast photomicrographs of neurospheres in control cultures (A) and in cultures treated with 200 μM suramin (B). Bar: 100 μm. (C) Graph showing the neurosphere diameter (in μm) in each experimental condition. Data are the mean ± SEM (n = 8, ** p < 0.01; Student’s t-test). (D) Graph showing the fold increase relative to the initial number of seeded NPCs in each experimental condition. Data are the mean ± SEM (n = 8, * p < 0.05; Mann–Whitney Rank Sum Test).