Figure 1.

Configuration of MEA, definition of glutamate measurements, and verification of MEA placement. A, Schematic drawing of a MEA tip. The platinum sites used as recording sites (yellow) were coated with glutamate oxidase (GluOx), which cause enzymatic breakdown of glutamate into α-ketoglutarate and peroxide (H₂O₂). The second pair of sites, labeled “reference sites,” were coated with BSA and glutaraldehyde, forming an inactive protein matrix and used for self-referencing. All four sites were then coated with a protective layer of mPD to block interferents. B, Schematic drawing of a KCl-induced glutamate release event. The glutamate amplitude was defined as the maximum increase in glutamate concentration compared with the baseline value recorded at the event of KCl ejection (arrow) minus the amplitude recorded at the corresponding reference channel. Tonic glutamate concentrations were recorded 10 data points before each KCl ejection minus the concentration recorded at the corresponding reference channel. T80 was defined as the time elapsed from the maximum amplitude until 80% of the glutamate peak had decayed. C, Histological verification of MEA placement in striatum and SNc by local application of methylene blue solution followed by Nuclear Fast Red counterstaining.