Motor nerve terminal staining combined with catecholamine histofluorescence or immunocytochemistry.

A number of excellent techniques are available to stain and characterize different types of neurons and nerve terminals. However, because these different techniques are frequently not compatible, their usefulness in determining the relationships between specific axons and neuromuscular junctions is often limited. The goal was to develop specific procedures for simultaneous visualization of different types of unmyelinated axons and motor nerve terminals in the same preparation. First we modified the formaldehyde/glutaraldehyde staining solutions of the aqueous aldehyde fluorescence technique (Faglu) to observe catecholamine containing axons in whole mount amphibian skeletal muscle. The compatibility of this modified staining solution with other histological procedures made it possible to stain both motor nerve terminals with tetrazolium salts and, in the same preparation, to observe unmyelinated axons with aldehyde-induced catecholamine histofluorescence. This same general formaldehyde/glutaraldehyde staining procedure was also used with immunocytochemical techniques to visualize fluorescent antibody stained nerves and motor nerve terminals in the same whole mount preparation.