The effects of (-)cathinone, the primary psychoactive alkaloid of the Khat plant, were compared to those of (+)amphetamine in the anterior caudate-putamen and the nucleus accumbens. In vivo microdialysis was used to measure extracellular levels of dopamine and metabolites in both regions of the brain simultaneously, after intraperitoneal administration of 0.8, 1.6 or 3.2 mg/kg of either drug (doses expressed as the salts). Both drugs increased levels of dopamine but decreased levels of metabolites in a dose-dependent manner. However, the relative magnitude of these effects depended upon the specific drug, the dose and area of the brain examined. At the largest dose used, amphetamine had a relatively greater effect than cathinone on dopamine in both caudate and accumbens. However, among smaller doses, this difference was only observed in the nucleus accumbens after administration of 1.6 mg/kg. The results also demonstrated a differential regional effect of both drugs at 3.2 mg/kg, in that both had a greater effect on dopamine in the caudate, as opposed to the accumbens. These findings demonstrate a functional heterogeneity of the striatum of the rat, that may be relevant to the understanding of both normal brain function and the neural responses to psychoactive drugs.