(A) Human NSC and its induced neuronal cells stained with DAPI, nestin, Sox2, ki67 or DCX. Scale bar, 20 μm. (B) qPCR quantification of NSC-expressing genes, nestin and Sox2. Data are mean + s.e.m., n = 3. ***p < 0.001 versus NSC. (C) qPCR quantification of neuron-expressing genes, DCX, MAP2, SYN1, and MAPT. Data are mean + s.e.m., n = 3. **p < 0.01; ***p < 0.001 versus NSC. (D) qPCR quantification of D2R in NSC and its induced neuronal cells. Data are mean + s.e.m., n = 3. ***p < 0.001 versus NSC. (E) Aβ generation after the challenge with vehicle (control), levodopa, piribedil or L685,458. Data are mean + s.e.m., n = 6. *p < 0.05; **p < 0.01; ***p < 0.001 versus the control. (F) Measurement of cellular γ-ecretase activity with vehicle (control), levodopa, piribedil, or L685,458 treatment. Data are mean + s.e.m., n = 4. *p < 0.05; **p < 0.01 versus the control. (G) Measurement of cellular BACE1 activity with vehicle (control), levodopa, piribedil, or BSI IV treatment. Data are mean + s.e.m., n = 4. ***p < 0.001 versus the control. (H) Western-blot showing the level of sAPPα in the culture medium and the expression of APP, BACE1, γ-secretase components including NCT, PS1-NTF, and Pen2 in the cell lysate. Actin was used as loading control.