Carbidopa

BBR, dopamine, and l-dopa were obtained from J&K Scientific Ltd (Beijing, China). 3,4-Dihydroxybenzylamine (as an internal standard, IS) was purchased from Alfa Aesar Chemical Co., Ltd (Ward Hill, MA, USA). Tyrosine, phenylalanine, α-methylphenylalanine, BLMA5 (an inhibitor of TH), and benserazide (an inhibitor of DDC) were obtained from Solarbio Life Science Co., Ltd (Beijing, China). ¹⁵N-Tyrosine (¹⁵N-Tyr, purity > 98%) was obtained from Cambridge Isotope Laboratories, Inc. (MA, USA). Cefadroxil, terramycin, and erythromycin were obtained from Solarbio Life Science Co., Ltd (Beijing, China). Carbidopa was from Selleckchem (Selleck Chemicals, Houston, TX, USA). P and MPTP-HCL were from Medchemexpress (MedChem Express LLC, Princeton, NJ, USA). The purity of the standards above was >98% (HPLC). The TH ELISA kit was from Shanghai Bangyi Biotechnology, Ltd (Shanghai, China). The DDC ELISA kit was from Shuangying Biological, Ltd (Shanghai, China). The PAH ELISA kit and BH₄ ELISA kit were obtained from Shanghai Fusheng, Ltd (Shanghai, China) and Shanghai Jianglai, Ltd (Shanghai, China), respectively. The ROS assay kit was from the Nanjing Jiancheng Bioengineering Institute (Nanjing, China).

Levodopa, bromocriptine, carbidopa, L-685,458, TAPI-1, Y-27632, and Forskolin (FSK) were purchased from Selleck Chemicals (Houston, TX, USA). Piribedil was from Tocris Bioscience (Bristol, UK). β-Secretase Inhibitor IV (BSI IV) was from Calbiochem (Hayward, CA, USA). Recombinant human BDNF, GNDF, IGF-I were from Peprotech (Rocky Hill, NJ, USA). cAMP and L-Ascorbic acid were from Sigma (St Louis, MO, USA). CellTiter-Glo was from Promega (Madison, WI, USA) and Effectene Transfection Reagent was purchased from QIAGEN (Hilden, Germany). Immunoblotting was performed with the following antibodies: anti-PS1 N-terminus (1–65) (PRB-354P, Covance, Davis, CA, USA); anti-APH1aL C-terminus (245–265) (PRB-550P, Covance); anti-NCT (N1660, Sigma); anti-Pen2 (P5622, Sigma); anti-BACE1 N-termimus (AP7774b, Abgent, Suzhou, China); anti-APP-CTF (A8717, Sigma); anti-sAPPα (secreted Amyloid Precursor Protein-α) (11088, IBL, Hokkaido, Japan); anti-HA (H6908, Sigma); anti-actin (A2066, Sigma); anti-D₂R (sc-9913, Santa Cruz Biotechnology, Santa Cruz, CA, USA). Immunostaining was performed with the following antibodies: anti-nestin (MAB353, Milipore, Darmstadt, Germany); anti-Sox2 (sc-17320, Santa Cruz); anti-Ki67 (556003, BD Transduction Laboratories, San Jose, CA, USA), and anti-Doublecortin (DCX) (sc-8066, Santa Cruz).