Pretreatment of rats with the noradrenergic neurotoxin DSP-4 selectively reduced regional levels of noradrenaline in the brain by more than 75%, and decreased the concentration of endogenous DA in microdialysates of the caudate nucleus and nucleus accumbens by 52% and 28%, respectively. Results support the hypothesis that central noradrenergic mechanisms facilitate nigrostriatal and mesolimbic dopamine transmission in vivo.