Medium II (serum-free medium): DMEM/F12 (Sigma–Aldrich) containing 2 mM glutamine, 2% NS-21 (MACS NeuroBrew-21 supplement (Miltenyi Biotec, Waltham, MA, USA)), 20 ng mL−1 basic fibroblast growth factor (bFGF; Sigma–Aldrich), 20 ng mL−1 epidermal growth factor (EGF; Sigma–Aldrich), 1% penicillin–streptomycin solution (Sigma–Aldrich).
Medium III: DMEM/F12 (Sigma–Aldrich) containing 2 mM glutamine, 2% NS-21 (MACS NeuroBrew-21 supplement (Miltenyi Biotec)), 20 ng ml−1 basic fibroblast growth factor (bFGF; Sigma–Aldrich), 1% penicillin–streptomycin solution (Sigma–Aldrich).
Medium IV: DMEM/F12 (Sigma–Aldrich) containing 2 mM glutamine, 2% NS-21 (MACS NeuroBrew-21 supplement (Miltenyi Biotec)), 1% penicillin–streptomycin solution (Sigma–Aldrich).
Medium V: DMEM/F12 (Sigma–Aldrich) containing 2 mM glutamine, 2%, 1% penicillin–streptomycin solution (Sigma–Aldrich).