Previous studies have provided anatomical evidence that the functional neuregulin receptor, ErbB4, is present within the ventral midbrain where it is co-localized to dopamine neurons of the substantia nigra and ventral tegmental area. In this study, we provide evidence that neuregulin1-beta (a.k.a. heregulin1-beta), a neuregulin-1 gene isoform that preferentially binds to and activates the ErbB4 receptor, evokes an almost immediate overflow of striatal dopamine when injected into a region just dorsal to the ipsilateral substantia nigra. These data are indicative that neuregulins can modulate the activity of mesostriatal dopaminergic neurons.