Amphetamine-evoked dopamine release from guinea-pig striatum is potentiated by environmental stress,a need for habituation with microdialysis equipment

Abstract

The microdialysis technique has been successfully applied to a study of amphetamine-evoked dopamine release in the striatum of conscious, freely-moving guinea-pigs. Basal levels of dopamine in guinea-pig striatal dialysates were comparable with published data from studies in rats. There were marked differences in the relative proportions of the two main dopamine metabolites in the guinea-pig compared to those reported previously in the rat, suggesting differences in the fate of dopamine between the species. Amphetamine caused an increase in dopamine and a decrease in dopamine metabolites in striatal dialysates. The increase in dopamine levels correlated with the increased incidence of head tics. Both the changes in dopamine levels and the incidence of head tics were less in animals which previously had been habituated with the experimental apparatus. Dopamine metabolite changes were unaffected by habituation, suggesting that the metabolites derive, at least in part, from sources other than released dopamine. These observations suggest that stress produced by a novel environment potentiate the response, both neurochemical and behavioural, to amphetamine. Care should be taken in the design of experiments to minimize stress factors.