Horseradish peroxidase as a retrogradely-transported, detailed dendritic marker.

A method is described that produces detailed 'Golgi-like' staining in neurons following retrograde transport of horseradish peroxidase (HRP). Of 4 commercially available HRP preparations, which were compared for their ability to produce solid neuronal staining in certain regions of the rabbit thalamus 48 h after striatal injection, two preparations (Miles Laboratories and Serva Biochemical) were found to be most efficient. When dimethylsulfoxide (DMSO) was used as the solvent for the injected HRP, a significant increase in the number of solidly labeled neurons in the thalamus was realized. Approximately 2% DMSO produced the greatest increase when compared with water as the solvent. Dendritic detail visualized by this method is shown to compare favorably with that produced by Golgi staining.