Synapses in the central nervous system are usually defined by presynaptic exocytotic release sites and postsynaptic differentiations. We report here a demonstration of dendrodendritic inhibition that does not engage a conventional synapse. Using amperometric and patch-clamp recordings in rat brain slices of the substantia nigra, we found that blockade of the dopamine transporter abolished the dendritic release of dopamine and the resulting self-inhibition. These findings demonstrate that dendrodendritic autoinhibition entails the carrier-mediated release of dopamine rather than conventional exocytosis. This suggests that some widely used antidepressants that inhibit the dopamine transporter may benefit patients in the early stages of Parkinson's disease.