Refereed paper
Carbon fibre micro-electrode and in vitro or in brain slices voltammetric measurement of ascorbate, catechol and indole oxidation signals: influence of temperature and physiological media

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Abstract

Carbon fibre micro-electrodes have been used to determine the influence of temperature and physiological media on the oxidation potential value of three carboxylic acids of physiological interest such as ascorbate (AA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindolacetic acid (5HIAA). Standard calibrations at room temperature (18–20°C) in phosphate buffered saline (PBS, pH 7·4), in Krebs (pH 7.4) or in artificial cerebral spinal fluid (ACSF, pH 7.4) have been compared with calibrations performed at 37°C under 95% oxygen, 5% carbon dioxide. Ex vivo experiments were then performed with the electrode inserted in the striatum of rat brain slices maintained in ACSF at 37°C under 95% oxygen, 5% carbon dioxide.

The results obtained from both in vitro and ex vivo experimentation indicate that the oxidation potential of peak 2 (DOPAC) is highly sensitive to changes in temperature and medium. Therefore the extrapolation from in vitro electrode calibrations performed in PBS at room temperature to ex vivo (brain slices) and possibly in vivo measurements of DOPAC oxidation should be reconsidered.

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    Citation Excerpt :

    Interestingly, the reverse was observed for the sensitivities of the acid metabolites (DOPAC, 5-HIAA). Crespi reported shifts in oxidation peaks and higher sensitivities using differential pulse voltammetry for aCSF that contained Ca2+ but not Mg2+, than in PBS that contained Mg2+ but not Ca2+ (Crespi, 1996). Such findings indicate that electrode surface interactions differ for anions and cations and are consistent with adsorption or repulsion effects at the modified (Nafion® or electrically pre-treated) CFE surface.

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