**2.8. Assessment of mitochondrial shape by electron microscopy**

hESC-derived neurons were cultured on matrigel-coated plastic coverslips and were exposed to either 20 μM or 100 μM ketamine or control conditions for 24 h. The cells were fixed at 4°C with 2% glutaraldehyde in 0.1 M sodium cacodylate buffer and postfixed for 1 h on ice with 1% osmium tetroxide. The cells were rinsed with distilled water and dehydrated using acetonitrile and graded methanol (50%, 20 min; 70%, 20 min; 95%, 20 min; 100% 3×, 20 min). The cells were embedded in epoxy resin (EMbed-812, Electron Microscopy Sciences, Hatfield, PA) and polymerized at 70°C overnight. Thin (60 nm) sections were cut and the sections were stained with lead citrate and uranyl acetate. The samples were imaged using a Hitachi H600 Electron Microscope.
