Figure 2.

Time course of the effects of 5 μM Aβ_1–42, 4 mM ketones, or the combination on the survival of hippocampal neurons in culture. ●, The mean control cell number/mm² with error bar indicating the SEM where n = 12. All statistical tests performed were Mann–Whitney U tests, and significance was taken to be P < 0.05. ○, The mean cell number after exposure to Aβ_1–42; ▴ after exposure to 5 μM Aβ_1–42 + 4 mM d-β-hydroxybutyrate and ▵ after exposure to 4 mM d-β-hydroxybutyrate alone. Exposure to 5 μM Aβ_1–42 significantly decreased the cell number compared with controls at 8 and 14 h as indicated by #. Addition of 4 mM d-β-hydroxybutyrate to cells exposed to 5 μM Aβ_1–42 increased the cell number compared with exposure of Aβ_1–42 alone at 8, 14, and 36 h as indicated by *. Addition of ketone bodies alone increased the cell number compared with controls as indicated by +. Our study therefore confirms the previous reports of the toxicity of Aβ_1–42 to cultured hippocampal neurons (28). In addition we show that ketones not only reverse the toxicity of Aβ_1–42, but act as a growth factor for neurons in culture.