Implantable microfabricated microelectrode arrays represent a versatile and powerful tool to record electrophysiological activity across multiple spatial locations in the brain. Spikes and field potentials, however, correspond to only a fraction of the physiological information available at the neural interface. In urethane-anesthetized rats, microfabricated microelectrode arrays were implanted acutely for simultaneous recording of striatal local field potentials, spikes, and electrically-evoked dopamine overflow on the same spatiotemporal scale. During these multi-modal recordings we observed 1) that the amperometric method used to detect dopamine did not significantly influence electrophysiological activity, 2) that electrical stimulation in the medial forebrain bundle (MFB) region resulted in electrochemically-transduced dopamine transients in the striatum that were spatially heterogeneous within at least 200 µm, and 3) following MFB stimulation, dopamine levels and electrophysiological activity within the striatum exhibited similar temporal profiles. These neural probes are capable of incorporating customized microelectrode geometries and configurations, which may be useful for examining specific spatiotemporal relationships between electrical and chemical signaling in the brain.

The ability to selectively deposit platinum black (PtB) on iridium microelectrodes and functionalize the surface for the purposes of choline sensing was investigated in this study. Platinum black was deposited by cycling 100–200 times between 0.5 V and −0.7 V in a solution of 1 mM K2PtCl6 in 0.1 M KCl. Deposition of PtB showed good chemical stability as well as good adhesion following insertion into agarose gel as a model for brain insertion. Electrode sites were also tested for their oxidative capabilities of hydrogen peroxide during which they showed high current change in response to small concentration changes - attributable to the high surface area of the PtB. Sites were then coated with an enzyme solution containing choline oxidase, and a permselective layer of meta-phenylenediamine was added to filter interferents. Electrode sites yielded a high sensitivity to choline compared to interferents including ascorbic acid and dopamine.

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