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Voltammetry has been widely used in attempts to measure catecholamine release in vivo. The voltammogram recorded in the rat striatum using carbon paste electrodes and linear sweep voltammetry with semidifferentiation consists of a number of separate peaks; changes in the height of the first of these peaks have been attributed to changes in catecholamine(More)
Brain glucose concentration was measured with an amperometric enzyme electrode using glucose oxidase (EC irreversibly adsorbed onto an organic conducting salt. The responses of the electrode and its stability both in vitro and in vivo are described. Parellel changes in brain glucose and blood glucose (measured in samples from an implanted(More)
The kinetic and thermodynamic features of reactions catalyzed by present-day enzymes appear to be the consequence of the evolution of these proteins toward maximal catalytic effectiveness. These features are identified and analyzed (in detail for one substrate-one product enzymes) by using ideas that link the energetics of the reaction catalyzed by an(More)
Circadian variations in the extracellular concentration of ascorbate and homovanillic acid in the striatum of unrestrained rats were measured simultaneously at 12 min intervals over periods of up to 48 h using carbon paste electrodes and microprocessor-controlled linear sweep voltammetry. Both compounds show a similar time course over a 24 h period,(More)
Changes in the height of peak 2 obtained using linear sweep voltammetry and carbon paste electrodes chronically implanted in discrete brain regions of the unrestrained rat were measured under a variety of conditions; in the past this peak has been attributed to the oxidation of 5-hydroxyindoleacetic acid (5-HIAA). Unilateral 5,7-dihydroxytryptamine(More)
Experimental properties of the peaks obtained with carbon paste electrodes and microprocessor-based linear sweep voltammetry in the rat brain have been compared with those predicted by a theoretical treatment of the problem which we have recently developed. This comparison indicates that the electrodes are situated in a restricted compartment and that the(More)
Voltammetry in vivo has suffered from the limitation that electrodes which give high resolution of the various electroactive compounds present in brain tissue have a short life span, and, conversely, that stable electrodes give poor resolution. Carbon paste electrodes and linear sweep voltammetry with semidifferentiation can resolve changes in the(More)
Circadian and amphetamine-induced changes in the extracellular concentration of ascorbate in the striatum and hippocampus of unrestrained rats were measured voltammetrically; the amphetamine-induced changes in striatal ascorbate were confirmed using a push-pull perfusion technique. Circadian changes in the level of blood plasma ascorbate, and the(More)
A number of advances have been made in the application of linear sweep voltammetry with carbon paste electrodes to the monitoring of ascorbate and monoamine neuroregulator metabolites in the brain of the freely-moving rat. These new measures are: the reduction of the sweep rate of 5 mV/s; the elimination of semidifferentiation in chronic recordings; the(More)
Linear sweep voltammograms were recorded in the striata of rats with a unilateral cortical lesion. The height of the ascorbate peak was 55% smaller on the lesioned side compared with the intact side, the homovanillic acid peak showed no significant change. The nocturnal increase in the release of striatal ascorbate was reduced by 80% on the lesioned side(More)