NEUROCHEMICAL APPLICATIONS OF ELECTROCHEMISTRY

The basal plane of pressure annealed pyrolytic graphite has been characterized as an electrode for use in liquid chromatography with electrochemical detection (LCEC) after pretreatment by anodic oxidation in a citrate-acetate buffer. This process results in increased electron transfer rates. LCEC is a sensitive method for the simultaneous analysis of dopamine (DA) and 5-hydroxytryptamine (5-HT) in, and their release from, striatal synaptosomes. Release elicited by several agents indicates stimulus-coupling and Ca('++) dependence.;The minimization of catalytic reactions, the recognition of the irreversibility of dihydroxyphenylacetic acid (DOPAC), and the shape of the current-voltage curves for well-behaved electrochemical systems can all be readily deduced from existing electrochemical theories. These relationships have been used to optimize the use of carbon fiber electrodes for in vivo electrochemistry. DA response provides the best data analysis method for interexperimental comparisons.;Control of temperature and the depth of anesthesia is mandatory for in vivo voltammetric experiments. Potential control during electrode implantation minimizes filming. In vivo backgrounds appear to be primarily composed of extracellular ascorbic acid (AA). The in vitro capacity of microelectrodes to distinguish DA from AA and DOPAC is maintained in vivo. Diffusion coefficients for these three compounds in the brain were determined.;In vivo electrochemistry with carbon fiber microelectrodes can provide new insights into the functioning of the intact mammalian central nervous system. The effects of amphetamine administration clearly demonstrate that at least one easily oxidized compound other than DA (probably AA) is released into the extracellular fluid. Data obtained from lesioned rats and from the cortex imply that DA markedly influenced the response to amphetamine injection. Inhibition of monoamine oxidase significantly shortened the electrochemical response to amphetamine.;Microvoltammetric electrodes constructed from carbon fibers exhibit properties which make them useful as in vivo probes of neuronal communication. Backstep correction provides residual current correction for pulsed wave forms. Pulsed wave forms prolong the usable lifetime of the electrode. Their small size, coupled with their rapid response, virtually eliminates artifacts caused by the oxidation of in vivo substances.