In Vivo Voltammetric Evidence that D-Amphetamine and Phenethylamine Release Ascorbic Acid into Striatal Extracellular Fluid

Abstract

Our laboratory uses the techniques of in vivo voltammetry and in vivo brain dialysis to measure changes in the extracellular concentrations of brain neurotransmitters, neurotransmitter metabolites and other compounds of interest. A typical in vivo striatal, linear sweep voltammogram consists of four distinct current peaks. The first peak, occurring at an applied voltage of about +0.12 volts vs an Ag/AgCl reference, results primarily from the oxidation of ascorbic acid with a smaller contribution from 3,4,-dihydroxy-phenylacetic acid and still less from the oxidation of dopamine. The height of the peak reflects the concentrations of these molecules at the tip of the graphite-paste working electrode. Changes in the height of this peak are proportional to changes in the extracellular concentrations of one or more of these unresolved constituants. in vivo brain dialysis, while employing a larger and less biocompatible probe, does not have the same problem with resolving these or other compounds since the probe physically removes a sample of extracellular fluid for laboratory analysis by whatever assay method is appropriate.