Differential pulse voltammetry in brain tissue: III. Mapping of the rat serotoninergic raphe nuclei by electrochemical detection of 5-HIAA.

Differential pulse voltammetry using a new type of carbon fiber electrode, electrochemically treated, is described. The working electrode contains 3 pyrolytic carbon fibers, and passes more current, thus giving a greater sensitivity (with the PRG5 Tacussel polarographic system) than the original monofiber electrodes. It is now possible to investigate brain areas where the monofiber electrodes, working near the limit of PRG5 sensitivity, showed too small a signal. These electrodes have, in addition, better mechanical resistance and can be used (after trypsin cleaning and further electrochemical treatment) for several experiments. Electrochemical measurements made in the nucleus raphe dorsalis before and after treatment with p-chlorophenylalanine, reserpine, clorgyline and clorgyline followed by reserpine, suggest that as in the striatum 5-hydroxyindoleacetic acid (5-HIAA) is mainly responsible for peak 3. The map of the raphe system made with this technique is well correlated with the serotoninergic system of the raphe: the highest peak heights are recorded in the raphe dorsalis.