L dopa

Nine-aminoacridine (9AA) was purchased from Merck Schuchardt (Hohenbrunn, Germany). 2, 5-dihydroxybenzoic acid (DHB) was purchased from Bruker Daltonics (Germany). Methanol, ethanol, and ultrapure water (Wako Pure Chemical Industries, Osaka, Japan) were used for the preparation of all solvents. All chemicals used in this study were of the highest purity available. For the Kawamoto method (Kawamoto and Shimizu, 2000 (link)), adhesive film (Cryofilm type IIC) was purchased from Leica Microsystems (Wetzlar, Germany). Standard chemicals of L-carnosine, inosine monophosphate, taurine, hydrocortisone, and corticosterone were purchased from Wako Pure Chemical Industries. Dopamine (Sigma Aldrich, St. Louis, MO, USA) and L-DOPA (Toronto Research Chemicals, Toronto, Canada) were also purchased and used in the study.

Experiments were performed as above, with the addition of the relevant metabolites (L-DOPA, 3,4-dihydroxyphenyl pyruvic acid (DHPPA), or 3,4-dihydroxyphenyl lactic acid (DHPLA)) at a final concentration of 1 mM, as well as 0.25% ascorbic acid to prevent L-DOPA oxidation. Compounds used for experiments and for MS analytical standards were sourced as follows: L-DOPA (Toronto Research Chemicals D533751), dopamine (Cayman Chemicals 21992), DHPLA (TargetMol T3227), DHPPA (AChemBlock M15562), HPLA (Sigma H3253).