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    Design of a voltammetry system for in vivo measurement of dopamine concentration
    (İstanbul Medipol Üniversitesi Fen Bilimleri Enstitüsü, 2018) Riaz, Raheel; Kocatürk, Mehmet
    Dopamine has a critical role in motor control, motor learning, reinforcement learning, cognition, attention and motivation. Consequently, the physiology of the dopaminergic system is an important and highly active research topic. Fast-scan cyclic voltammetry (FSCV) technique enables in vivo measurement of dopamine concentration with high, subsecond temporal resolution. In this study, our aim was to propose a low-cost and practical FSCV system that enables the recording of the phasic changes in dopamine concentration in the rat brain during behavioral experiments. We developed the voltammetry hardware using a microcontroller and a combination of analog integrated circuits (ICs) to generate a triangular voltametric waveforms phase-locked to mains frequency and to apply these waveforms to a carbon ?ber microsensor. The voltammetric current through the microsensor is converted to voltage, ampli?ed, ?ltered using the hardware and then fed to a data acquisition card on a PC. A LabVIEW application is also developed to control the data acquisition hardware, digital ?ltering of the recorded signals and storage of the data. In order to validate the practicality of the system, we chronically implanted one rat with carbon ?ber microsensor in the ventromedial striatum (VMS) and recorded the voltammetric signals 1) in response to presentation of unexpected primary rewards (unconditioned stimuli), 2) in response to presentation of reward predictive stimuli (cue light) and 3) during electrical stimulation of dopaminergic pathway. Based on 5 recording sessions in which unexpected rewards were presented and 5 recording sessions in which predictive stimuli were presented, the phasic increase in the dopamine concentration was measured as 50.5±13.1 nM and 40.2±13.9 nM, respectively. The peak increase in dopamine concentration with electrical stimulation of the dopaminergic pathway during implantation surgery was measured as 132.8 nM. Our results based on the recordings from one rat indicate that phasic increases in dopamine concentration in the VMS in response to delivery of unexpected rewards and reward predictive stimuli can be detected using the proposed system. The cost of the present FSCV system is approximately $1200.