Hoechst 33342 as a marker for imaging neurites of Dorsal Root Ganglion in vitro

Fluorescent markers, generally targeting neurotubules, are used to visualize the radiating crown of growing neurites that is produced by dorsal root ganglion cells in vitro. Hoechst 33342 (2'-[4-ethoxyphenyl]-5-[4-methyl-1-piperazinyl]-2,5'-bi-1H-benzimidazole trihydrochloride trihydrate) is a widely used fluorescent DNA marker that stain both live and fixed nuclei. We have recently found that H33342 can visualize the neurites of DRG too, but only when they are fixed in formalin. Images have a good signal-to-noise ratio. We noticed that besides H33342 being a specific marker for DNA, it also stains the transmembrane P-glycoprotein (P-gp) which is involved in the active pump-out of alien molecules from the cytoplasm; so, H33342 remains associated with P-gp after fixation. P-gp is quite ubiquitous in healthy cells and, notably, P-gp has been detected in DRG of several species as well as in human DRG. The use of H33342 as a staining for neurites of DRG in fixed samples could have a practical value due to its widespread use and its better affordability compared to other fluorescent markers for neurites.