Tract-tracing with horseradish peroxidase in the postmortem human brain

A method for tracing central nervous system fiber tracts in the postmortem human brain is described. Fresh human brains with minimal postmortem delay (3-7 h) were used. Horseradish peroxidase (HRP) crystals were applied directly to the cross-sectioned face of the left dorsal columns at cervical spinal cord or caudal medullary levels. After 5 min, the HRP was washed off and the brainstem incubated in the cold for 24-48 h prior to sectioning and developing with diaminobenzidine. Reaction product was observed in nerve fibers of the ipsilateral dorsal columns, dorsal horn and the nuclei cuneatus and gracilis, up to 2.0 cm from the application point. The method should be useful for tract-tracing throughout the human brain.