The monitoring of ascorbate and monoamine transmitter metabolites in the striatum of unanaesthetised rats using...

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 concentration of ascorbate, deaminated and methylated metabolites of catecholamines, and the 5-hydroxyindoles in vivo and give stable recordings over many weeks. However, these changes in concentration are difficult to quantify. We have now developed the method further with the application of microprocessor technology. Microprocessor-based voltammetry and data analysis enable one to quantify changes in the concentration of electroactive species in complex mixtures where there are no separate oxidation peaks for the components; this has been achieved both in vitro and in vivo. Changes in dopamine release from the striatum have been monitored continuously over 48 h in unanaesthetised rats after the intraperitoneal administration of haloperidol. Carbon paste electrodes and microprocessor-controlled linear sweep voltammetry facilitates the quantitative, continuous monitoring of the extracellular concentration of ascorbate, the deaminated and methylated metabolites of catecholamines, and the 5-hydroxyindoles in the brain of unrestrained animals.