Electrochemical detection of dopamine release in the striatum of freely moving hamsters

It was proposed to characterize the electrochemical signal recorded with a multifibre carbon electrode chronically implanted in the striatum of freely moving hamsters when the electrode potential was increased from-175 mV to +325 mV. Both in vitro calibration in standard solutions of oxidative molecules and in vivo pharmacological studies were used for this purpose. Results show that after an appropriate electrochemical treatment of the electrode in vitro the oxidation of dopamine (DA) produces a characteristic signal, whereas standard solutions of DOPAC and ascorbic acid produce no response. The electrochemical response recorded in vivo from the striatum of freely moving hamsters when the potential of the electrode is raised from-175 mV to +325 mV seems to correspond to the in vitro response to DA. This in vivo response diminished considerably following the destruction of the nigro-striatal dopaminergic neurones by means of an intranigral injection of 6-hydroxydopamine, while the striatal levels of ascorbic acid are not affected by the lesion. The administration of both amphetamine (3 mg/kg, i.p.) and the inhibitor of monoamine oxidases, pargyline (90 mg/kg i.p.), enhances the amplitude of the electrochemical signal. These results suggest that the electrochemical response recorded with our device in the striatum of the freely moving hamster corresponds to the oxidation of DA and not that of its metabolite DOPAC. Ascorbic acid is also very unlikely to contribute to the signal since the dopaminergic lesion does not alter the striatal level of this acid and since pargyline increases the amplitude of the signal.