Pharmacological characterisation of dopamine overflow in the striatum of the normal and MPTP-treated common marmoset, studied in vivo using fast cyclic voltammetry, nomifensine and sulpiride.

The in vivo measurement of electrically-evoked dopamine overflow was measured for the first time in the striatum of control and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated common marmosets using fast cyclic voltammetry at untreated carbon-fibre microelectrodes, (7 microm, o.d.). The identity of dopamine was confirmed using electrochemical, pharmacological and histological criteria and complied with rat data from earlier studies. Dopamine overflow depended on the intensity, number of pulses, and frequency of the applied stimuli. Maximum dopamine overflow occurred using 1.0-2.0 mA, 200 micros pulse width, 150-200 pulses at 80-120 Hz stimulation of the medial forebrain bundle. Evoked dopamine overflow in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated marmosets showed a similar electrochemical and pharmacological profile compared to healthy controls, albeit the concentration detected was significantly reduced. The catecholamine uptake blocker, nomifensine, significantly increased the dopamine signal in control marmosets. However, in contrast, nomifensine had no significant effect on evoked dopamine overflow in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated marmosets. Apart from demonstrating that fast cyclic voltammetry with electrical stimulation can be reliably used to monitor dopamine overflow within the primate brain, our results describe for the first time the technical prerequisites for the fast cyclic voltammetric technique in the non-human primate brain.