In vivo electrochemical detection of catechols in several dopaminergic brain regions of anaesthetized rats.

Differential pulse voltammetry (DPV) was used in conjunction with electrochemically treated carbon fibre microelectrodes to monitor in vivo the catechols (CA) levels in the substantia nigra (SN), ventral mesencephalic tegmentum (VMT) and nucleus accumbens of anaesthetized rats. The current corresponding to CA oxidation was always closely related to the anatomical localisation of the dopaminergic neurons e.g. it was maximal in tht pars compacta of the SN. In addition, the current was selectively suppressed in all regions after 6-OHDA-induced degeneration of the dopaminergic neurons and after pargyline treatment. These findings together with our previous results suggest that 3,4-dihydroxyphenylacetic acid (DOPAC) is the main contributor to the CA oxidation current measured in these areas. Haloperidol induced a significant increase of the CA signal in the nucleus accumbens (+70%) but not in the SN or VMT. The DOPAC concentrations declined exponentially after pargyline administration. The fractional rate constant of DOPAC, computed from these results appears to be similar in all regions studied except for n. accumbens where the low rate of disappearance might be responsible for the high DOPAC concentration measured in this area. In conclusion, DPV with electrochemically treated carbon fibre electrodes is a useful means of monitoring extracellular DOPAC levels in dopaminergic brain regions.