Labeling of human retinohypothalamic tract with the carbocyanine dye, DiI.

The carbocyanine dye, DiI, was used to demonstrate human retinohypothalamic tract (RHT) projections in 6 normal human postmortem brains. In 5 of 6 brains, labeling was seen extending from the site of implantation in the distal optic nerve to both the ipsilateral and contralateral suprachiasmatic nuclei. This study confirms the presence of RHT projections in humans, and demonstrates the usefulness of DiI for neuronal tracing in human postmortem tissue.