Figure 3.

Representative in vitro calibration of the glutamate-sensitive MEA immediately prior to implantation into the PFC. Top two tracings: glutamate-sensitive (GluOx) recording channels. Bottom two tracings: sentinel background channels. Arrows indicate addition of various substances to the calibration beaker. Current (pAmp) is depicted along the vertical axis, and time (sec) along the horizontal axis. Successive additions of glutamate (raising concentration by 20 μM/aliquot) produce a linear increase in the glutamate signal. No glutamate-related changes in current are detected on the two sentinel channels. Note equivalent sensitivities to the reporter molecule H₂O₂ on all four channels. meta-Phenylenediamine (m-PD) (see Methods) coating blocked access of negatively charged in vivo interferents such as ascorbic acid (AA) or dopamine (DA).