Characterizing Self-Inserting Carbon-Fiber Microelectrode Arrays for Fast-Scan Cyclic Voltammetry

The ability to monitor brain neurotransmitters with high fidelity is critical for establishing the neural underpinnings of behavior and pathology. Fast-scan cyclic voltammetry (FSCV) is an electroanalytical technique that relies on sweeping electrical potentials to drive rapid oxidation and reduction of electroactive neurochemicals. FSCV applications are typically limited by their ability to measure from one to two recording sites using a well-established microsensor, the carbon-fiber microelectrode (CFM). When coupled to FSCV, the CFM provides exquisite spatial, temporal, and chemical resolution in vivo. Recent advances have led to the development of self-inserting (i.e., without the requirement for a shuttle) carbon-fiber microelectrode arrays (CF-MEAs) capable of measuring up to sixteen sites simultaneously. Here we characterize CF-MEAs for measuring dopamine (DA), a neurotransmitter critical for locomotion, motivation, and cognition that also plays a substantive role in the pathologies of Parkinson’s disease, substance use disorder, and schizophrenia. In general, performance of CF-MEAs for FSCV DA monitoring assessed with flow injection analysis, a “beaker” technique that directs a laminar bolus of dopamine to the sensing surface, compared favorably with those of the conventional CFM. Measurements in the urethane-anesthetized rat also suggest that CF-MEAs are capable of capturing heterogeneous DA signals in the striatum, a brain region densely innervated by DA neurons and heavily implicated in reward learning, with high fidelity to conventional CFMs but simultaneously at multiple sites across a much broader measurement field. We conclude that CF-MEAs perform favorably in comparison to CFMs with regard to temporal response, DA sensitivity, background signal, signal-to-noise ratio, and electrochemistry. Moreover, CF-MEAs have a distinct advantage over CFMs to characterize the heterogeneous nature of DA signaling in vivo through their ability to simultaneously monitor a 1.5 mm mediolateral span of the brain in 100-μm increments