Differential pulse voltammetry in vivo with working carbon fiber electrodes: 5-hydroxyindole compounds or uric acid detection?

Abstract

Differential pulse voltammetry was performed in rats chronically implanted with carbon fiber electrodes in the caudate (n.Cd) and raphe dorsalis (n.RD) nuclei. The electrochemical signal obtained at the +300 mV potential (peak 3) in animals implanted for more than one week (long term chronic conditions, greater than 7 days) could be dependent upon the extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in n.Cd and n.RD. This result was obtained despite the tendency of Pargyline to increase n.Cd and n.RD endogenous concentrations of Uric Acid (UA) measured by High Performance Liquid Chromatography (HPLC). In contrast, in animals implanted for less than one week (short term chronic conditions, less than 7 days) peak 3 recorded in the same structure could be dependent upon extracellular fractions of 5-HIAA and UA since consecutive injections of Pargyline and Allopurinol are necessary to suppress this signal. The source of extracellular UA measured in brain by voltammetry, in such short term chronic conditions, might result from surgical trauma.

Differential responsiveness of the rat dorsal and median raphe 5‐HT systems to 5‐HT1 receptor agonists and p‐chloroamphetamine

“…Identification of the nature of the 300 mV oxidative peak in the hippocampus Previous results from our laboratory and others demonstrated that by using carbon fiber electrodes and DPV the levels of extracellular 5-HIAA can be monitored in various regions of the rat brain (for a review, see Maidment et al, 1986). Despite the fact that uric acid seems to contribute about 30% to this signal, the presence of this purine metabolite did not prevent the detection of pharmacologically induced alterations in 5-HT metabolism in the cerebral cortex, the raphe nuclei, and the spinal cord Cespuglio et al, 1986;Rivot et al, 1987). Consistent with these previous reports, indoleamines also accounted for at least 50% of the 300 mV peak in the dentate gyrus ( Fig.…”

Rotating disk electrode voltammetric measurements of serotonin transporter kinetics in synaptosomes

“…Most electrochemical methods for measuring 5-HT in vivo and in vitro treat electrodes with Nafion to increase selectivity over their acid metabolites (Cahill et al, 1996; Cespuglio et al, 1986; Crespi et al, 1983; Daws and Toney, 2007; John et al, 2006; John and Jones, 2007; Perez and Andrews, 2005; Rivot et al, 1995). Nafion was not used here because the signal was obtained from direct exogenous addition of 5-HT.…”

Endogenous Release of Neuronal Serotonin and 5‐Hydroxyindoleacetic Acid in the Caudate‐Putamen of the Rat as Revealed by Intracerebral Dialysis Coupled to High‐Performance Liquid Chromatography with Fluorimetric Detection

“…The basal levels of 5-HIAA in the rat striatum reported in studies based on in vivo voltammetry (Cespuglio et al, 198 1) are generally higher than the levels estimated on the basis of the microdialysis technique (Zetterstrom et al, 1983Hutson et al, 1985;Marsden et al, 1986, Strecker et al, 1987. This discrepancy can be explained to some extent by the contribution of uric acid to the indole peak in the voltammogram (Kennett and Joseph, 1982;O'Neill et al, 1984;Cespuglio et al, 1986;Rivot et al, 19871, but also by the difficulties in establishing the actual in vivo recovery for the dialysis probe. For a single compound, dissolved in a medium similar in composition to the perfusion fluid, the recovery will depend not only on the biochemical properties and concentration of the compound, but also on the properties of the membrane, the size, shape, and design of the probe, and the perfusion rate (Ungerstedt, 1984).…”