Fig. 6. Lithium inhibits the initial neurite outgrowth of PC12 cells and neural progenitor cells derived from adult rat hippocampus. (A) Excess myo-inositol administration failed to rescue the inhibition of neurite outgrowth of PC12 cells by LiCl. PC12 cells induced to differentiate by NGF in the presence of excess myo-inositol (20 mM) were left untreated (NGF + myo) or simultaneously treated with lithium (NGF + myo + LiCl) for 3 days. Scale bar: 25 µm. (B) AHPs expanded by FGF-2 (10 ng/ml) were replated on culture slides with 40 ng/ml FGF-2 with or without 20 mM LiCl for 1 day. (a,b) Cell morphologies of AHPs without (a) or with (b) lithium. Scale bar: 10 µm. (c) Quantitative data showing the percentage of neurite-bearing cells. PC12 cells possessing one or more neurites of a length more than 1.5-fold the diameter of the cell body were scored as positive. Lithium almost completely blocked initial neurite outgrowth of AHPs (mean±s.e.m.). P<0.001.