Brain Research, 159 (1978) 55-68 55 © Elsevier/North-Holland Biomedical Press IN VIVO VOLTAMMETRY: MONITORING OF DOPAMINE METABOLITES IN CSF FOLLOWING RELEASE BY ELECTRICAL STIMULATION R. MARK WIGHTMAN*, ELAINE STROPE, PAUL PLOTSKY and RALPH N. ADAMS** Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (U.S.A.) (Accepted April 13th, 1978) SUMMARY An in vivo electrochemical system which continuously records the concentration of metabolites of biogenic amines in small animal CSF is described. A small electrode, immersed in lateral ventricle CSF through a guide cannula, measures the amine metabolites by voltammetric oxidation. The detailed results of HVA release following electrical stimulation of the nigrostriatal pathway in rats are presented and compared with previous perfusion data. All the electrochemical results are verified by independent liquid chromatographic (chemical) analysis. INTRODUCTION A brief report recently described an in vivo voltammetric electrode which measures the concentration of biogenic amines and their metabolites in small animal ventricular CSF. This on-line, almost continuous readout of concentrations requires neither radiotracer precursors nor perfusions z~. Neurotransmitter metabolites released into the CSF can be a sensitive indicator of neuronal functioning in nearby diencephalon structures -- although there are many pitfalls in proper interpretation of the results as pointed out in Baldessarini's recent critical review 3. Thus the new and different information acquired with the voltammetric method requires careful exami- nation and correlation with that obtained from previous perfusion studies. A thorough description of the voltammetric method and its results is given herein. In the present application an inert working electrode is inserted through a previously implanted guide cannula so that the active electrode surface is just immersed in ventricular CSF. Auxiliary and reference electrodes (usually Ag/AgC1) are placed in convenient locations. A potentiostat, analogous to the voltage clamp * Present address: Department of Chemistry, Indiana University Bloomington, Ind. 47401, U.S.A. ** Author to whom correspondence should be addressed.