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Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.

ABSTRACT: Fast-scan cyclic voltammetry (FSCV) with carbon-fiber microelectrodes has been successfully used to detect catecholamine release in vivo. Generally, waveforms with anodic voltage limits of 1.0 or 1.3 V (vs Ag/AgCl) are used for detection. The 1.0 V excursion provides good temporal resolution but suffers from a lack of sensitivity. The 1.3 V excursion increases sensitivity but also increases response time, which can blur the detection of neurochemical events. Here, the scan rate was increased to improve the sensitivity of the 1.0 V excursion while maintaining the rapid temporal response. However, increasing scan rate increases both the desired faradaic current response and the already large charging current associated with the voltage sweep. Analog background subtraction was used to prevent the analog-to-digital converter from saturating from the high currents generated with increasing scan rate by neutralizing some of the charging current. In vitro results with the 1.0 V waveform showed approximately a 4-fold increase in signal-to-noise ratio with maintenance of the desired faster response time by increasing scan rate up to 2400 V/s. In vivo, stable stimulated release was detected with an approximate 4-fold increase in peak current. The scan rate of the 1.3 V waveform was also increased, but the signal was unstable with time in vitro and in vivo. Adapting the 1.3 V triangular wave into a sawhorse design prevented signal decay and increased the faradaic response. The use of the 1.3 V sawhorse waveform decreased the detection limit of dopamine with FSCV to 0.96 ± 0.08 nM in vitro and showed improved performance in vivo without affecting the neuronal environment. Electron microscopy showed dopamine sensitivity is in a quasi-steady state with carbon-fiber microelectrodes scanned to potentials above 1.0 V.

SUBMITTER: Keithley RB

PROVIDER: S-EPMC3089759 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.

Keithley Richard B RB Takmakov Pavel P Bucher Elizabeth S ES Belle Anna M AM Owesson-White Catarina A CA Park Jinwoo J Wightman R Mark RM

Analytical chemistry 20110407 9

Fast-scan cyclic voltammetry (FSCV) with carbon-fiber microelectrodes has been successfully used to detect catecholamine release in vivo. Generally, waveforms with anodic voltage limits of 1.0 or 1.3 V (vs Ag/AgCl) are used for detection. The 1.0 V excursion provides good temporal resolution but suffers from a lack of sensitivity. The 1.3 V excursion increases sensitivity but also increases response time, which can blur the detection of neurochemical events. Here, the scan rate was increased to ...[more]

PMID: 21473572

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Project description:Dopamine D2 and D3 autoreceptors are located on pre-synaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate-putamen and nucleus accumbens core and shell. The dopamine D2 agonists (-)-quinpirole hydrochloride and 5,6,7,8-Tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate-putamen and nucleus accumbens (core and shell) based on their EC(50) and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-Tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (+/-)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in caudate-putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate-putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.3 muM lowered the uptake rate in caudate-putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the pre-agonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonist as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum.

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Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.

Publications

Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.

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