title: Temporal differentiation of pH-dependent capacitive current from dopamine.
abstract: Voltammetric recording of dopamine (DA) with fast-scan cyclic voltammetry (FSCV) on carbon fiber microelectrodes have been widely used, because of its high sensitivity to dopamine. However, since an electric double layer on a carbon fiber surface in a physiological ionic solution behaves as a capacitor, fast voltage manipulation in FSCV induces large capacitive current. The faradic current from oxidation/reduction of target chemicals must be extracted from this large background current. It is known that ionic shifts, including H(+), influence this capacitance, and pH shift can cause confounding influences on the FSCV recordings within a wide range of voltage. Besides FSCV with a triangular waveform, we have been using rectangular pulse voltammetry (RPV) for dopamine detection in the brain. In this method, the onset of a single pulse causes a large capacitive current, but unlike FSCV, the capacitive current is restricted to a narrow temporal window of just after pulse onset (<5 ms). In contrast, the peak of faradic current from dopamine oxidation occurs after a delay of more than a few milliseconds. Taking advantage of the temporal difference, we show that RPV could distinguish dopamine from pH shifts clearly and easily. In addition, the early onset current was useful to evaluate pH shifts. The narrow voltage window of our RPV pulse allowed a clear differentiation of dopamine and serotonin (5-HT), as we have shown previously. Additional recording with RPV, alongside FSCV, would improve identification of chemicals such as dopamine, pH, and 5-HT.
authors.affiliation: Department of Neurophysiology, Juntendo University School of Medicine , Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yoshimi
authors.forename: Adam
authors.initials: A
authors.lastname: Weitemier
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D000077482:Carbon Fiber; D004298:Dopamine / Q000032:analysis*; D055664:Electrochemical Techniques; D006863:Hydrogen-Ion Concentration; D008839:Microelectrodes; D010084:Oxidation-Reduction; D012701:Serotonin / Q000032:analysis
chemical_list: D000077482:Carbon Fiber; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D002244:Carbon; D001205:Ascorbic Acid; D002118:Calcium; D004298:Dopamine