Fast scan cyclic voltammetry (FSCV) and carbon-fiber microelectrodes (CFMEs) have been utilized to detect several important neurochemicals in vivo. However, this method is limited due to the ability to discriminate dopamine from several of its metabolites. Polymers such as PEDOT, Nafion, and Polyethyleneimine (PEI) will be utilized to modify microelectrodes to measure neurochemicals by altering the size, charge, and morphology of the electrode surface. Moreover, novel waveform development will also be utilized to measure many neurochemicals and metabolites such as dopamine, norepinephrine, normetanephrine, 3-methoxytyramine (3-MT), homovanillic acid (HVA), 3,4 dihydroxyphenylacetic acid (DOPAC), and other metabolites. Dopamine will be differentiated from its metabolites based on the shape and position of the cyclic voltammogram, which is a chemical fingerprint of neurotransmitter detection. We have measured the stimulated release of dopamine in zebrafish retina, which illustrates this technique in biological tissue. The multiplexing of dopamine metabolites and dopamine will have many implications in better understanding complex disease, behavioral, and pharmacological states.This work will also discuss the development of multielectrode arrays (MEAs) for neurotransmitter detection with fast scan cyclic voltammetry in multiple brain regions simultaneously. These arrays will be coupled to multichannel potentiostats from Pine Research. Parylene and silicon insulated carbon fiber microelectrode arrays were shown to be able to measure neurochemicals in multiple brain regions simultaneously when coupled with multichannel potentiostats. Moreover, we have utilized techniques such as plasma enhanced chemical vapor deposition (PECVD) to deposit conductive carbon nanospikes onto the surface of existing metal multielectrode arrays to give them dual functionality as neurotransmitter sensors with FSCV in addition to being used primarily for electrical stimulation and recording. Other assays have shown the utility of electrodepositing carbon nanotubes and polymers such as PEDOT to coat metal arrays with carbon to give them dual sensing capabilities. Applications of measurements with these carbon electrodes will be illustrated with measurements in mouse brain slices, zebrafish brain and retina, DNA, amino acids, and neuropeptides. Figure 1