IN addition to the axons which project to the nucleus caudatus1,2, the dopamine (DA)-containing perikarya of the substantia nigra have extensive dendritic processes. These dendrites, observed after Golgi staining3–5 and by electron microscopy3,4, contain relatively large amounts of DA—revealed by histofluorescence6—and vesicle–like structures4. The DA seems to be stored in reserpine–sensitive structures6. The question has arisen whether DA can be released from the dendritic processes, as well as from nerve terminals of the nucleus caudatus7,8. Our investigation of the metabolism of released DA suggests that it can.