In vivo voltammetry with electrodes that discriminate between dopamine and ascorbate.

Untreated carbon-fiber voltammetric electrodes have been employed as chemical sensors of easily oxidized compounds in the brains of rats anesthetized with chloral hydrate. These electrodes can be used to distinguish dopamine from ascorbate and dihydroxyphenylacetate by the shape of the voltammograms. The electrodes are shown to provide a reproducible response to different neuronal stimuli. The rapid release of dopamine in the caudate nucleus can be measured following a local application of potassium chloride. Intraperitoneal injections of amphetamine also induce an increase of easily oxidized compounds; however, the voltammetry suggests that ascorbic acid, rather than dopamine, is the primary substance detected. Measurements in the cortex or in the caudate nucleus of animals lesioned by prior injection of 6-hydroxydopamine show that a substance with voltammetric properties identical to those of ascorbic acid also increases in concentration in these areas as a result of amphetamine administration.