3-hydroxybutyrate protects neonatal rat hippocampal neurons from cell death induced by glucose deprivation. Neonatal rat hippocampal neurons (A) or LNT-229 glioma cells (B) were cultured at different glucose concentrations in the absence (control) or presence of 3-hydroxybutyrate (3OHB, 5 mM). MTT reduction was determined 120 h (hippocampal neurons) or 72 h (LNT-229) after exposure (mean and standard deviation, ** p < 0.01). (C) Glioma cells were grown in medium containing 0 mM, 1 mM, 2.5 mM, 5 mM, 10 mM or 25 mM glucose, supplemented with 3-hydroxybutyrate (3OHB, 5 mM) or not. Cell density was assessed by crystal violet staining at day 1, 2, 3, 4, 6 and 8 after exposure, as shown here for LNT-229 cells (mean and standard deviation). (D) Primary rat astrocytes were treated similarly and crystal violet staining was performed at day 2, 4, 6, 8, 10 and 12 (mean and standard deviation). For a clearer arrangement, 10 mM and 25 mM glucose conditions, showing no difference in cell density between control and 3-hydroxybutyrate supplementation, are not displayed.