Abstract
Carbon fiber microelectrodes (CFEs) are useful when combined with electrochemical techniques for measuring changes in neurotransmitter concentrations. We addressed conflicting details regarding the use of CFEs. Experimental groups consisted of CFEs at different ages (1 week, 1 month, or 2 months), cleaned in solvents (isopropanol or xylene), and exposed to in vitro use (flow cell calibrations) or in vivo use (in brain tissue). In order to determine if any of these factors affect CFE sensitivity, the present study utilized fixed potential amperometry and a flow injection system to calibrate CFEs for the measurement of dopamine. The sensitivity index (nA/μM per 100 μm of exposed carbon fiber) was not affected by the age of CFEs or pre-cleaning with xylene or isopropanol. CFE sensitivity of the in vitro exposure group also did not differ from untreated CFEs, indicating the calibration process did not alter sensitivity. However, in vivo use in brain tissue did reduce sensitivity. This effect was negated and sensitivity restored by cleaning CFEs in isopropanol or xylene following in vivo brain recordings. Given that variations in CFE sensitivity can skew results, our findings can help standardize CFE use and explain discrepancies between researchers.
Highlights
fast scan cyclic voltammetry (FSCV) involves applying a potential in a series of triangular-shaped waveforms, for example cycling from −0.4 mV to 1.2 mV and back to −0.4 mV, allowing for exact measurement of the analyte’s oxidation and reduction, providing a chemical selectivity lacking in fixed potential amperometry
Carbon fiber microelectrodes (CFEs) constructed 1 or 2 months prior to calibration had no significant decrease in ability to detect dopamine oxidation compared to CFEs constructed within 1 week of use (0.0584 ± 0.006) (F = 0.26, p = 0.77) (Figure 1(b))
In vivo experimental exposure in brain tissue did reduce CFE sensitivity, but this effect is negated if CFEs are cleaned with either isopropanol or xylene following use in brain tissue
Summary
The most common techniques utilizing CFEs for the measurement of neurotransmitter release include fixed potential amperometry (sometimes called continuous amperometry) [5] [6] [7] and fast scan cyclic voltammetry (FSCV) [8] [9]. FSCV involves applying a potential in a series of triangular-shaped waveforms, for example cycling from −0.4 mV to 1.2 mV and back to −0.4 mV, allowing for exact measurement of the analyte’s oxidation and reduction, providing a chemical selectivity lacking in fixed potential amperometry. Each electrochemical technique has advantages and disadvantages, but both are especially well known as being effective and reliable for quantifying phasic dopamine release using CFEs [10]
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