Fast in vivo monitoring of electrically evoked dopamine release by differential pulse amperometry with untreated carbon fibre electrodes.

Differential pulse amperometry has previously been used in combination with electrochemically treated carbon fibre electrodes. In order to improve the time resolution, this technique was combined here with untreated electrodes. Dopamine release was evoked in the nucleus accumbens of rats anaesthetized with urethane by electrical stimulation of the mesolimbic dopaminergic pathway. The differential oxidation current appearing at +200 mV was recorded every 1 s and was proportional to the dopamine concentration from 0.5 to 50 microM. At this voltage these untreated electrodes were not sensitive to the main catechol metabolite (DOPAC) and poorly sensitive to ascorbic acid. The electrically evoked increase in the oxidation current corresponded exclusively to dopamine. It was enhanced by nomifensine, amphetamine, haloperidol and pargyline and reduced by alpha-methyl-p-tyrosine (A-MPT). The results show that the evoked DA release was facilitated by increasing the stimulation frequency from 10 to 40 Hz. The method was sufficiently sensitive to detect dopamine release evoked by electrical stimulation at 10 Hz and its time resolution was 1 s.