Fig. 1. Propofol did not change the proportion of cells in S-phase, but did cause dose-dependent toxicity in proliferating neural precursor or stem cells (NPCs). (A ) NPCs were given a pulse of 5-bromo-2-deoxyuridine (BrdU) after 6 or 24 h exposure to propofol then fixed for immunocytochemistry with anti-BrdU antibody (A1 ) or 4’,6-diamidino-2-phenylindole (A2 ). Overlayed images (A3 ) were then photographed and the nuclei were counted. (B ) The number of cells that incorporated BrdU was not different in cells treated with propofol versus dimethyl sulfoxide carrier only. (C ) NPCs were exposed to increasing concentrations of propofol for 6 h then assayed for lactate dehydrogenase release into the media. All values are relative to complete lysis of cells, which was set at 100%. Increasing the concentration of propofol increased the amount of lactate dehydrogenase released in the media. (D ) The low end of the dose–response curve was further investigated, and 7.1 µM propofol was found to be different from 0 µM propofol (carrier only) (Dunnett test). (E ) Diprivan, a clinically used formulation of propofol, produced a similar result when compared with control (Dunnett test). *P < 0.05, **P < 0.01. DMSO = dimethyl sulfoxide; LDH = lactate dehydrogenase.