Fluorescent AM1-43 and FM1-43 probes for dental sensory nerves and cells: Their labeling mechanisms and applications

SummaryThis mini-review first introduces the fluorescent styryl dyes, AM1-43 and FM1-43, which stain a variety of sensory cells and tissues including sensory nerve fibers. Second, a photoconversion method for ultrastructural localization of the dyes within cells is described as an example of an applied technique of these fluorescent dyes. Third, the following labeling mechanisms of FM1-43, AM1-43 and related dyes are introduced: (1) internalization of the dyes via endocytosis, (2) direct dye internalization via cation channels in the plasma membrane, (3) labeling by membrane insertion of the dye molecules and extensive membrane accumulation in cell membranes such as myelin of nerves. Fourth, the application of AM1-43 as a tool for observation of the innervation of periodontal ligaments and dental pulp is introduced and a possible candidate dye-permeable cation channel protein is suggested. Fifth, several topics which should be focused on in future studies are raised. Accumulation of these dye applications may shed new light on further understanding of dental tissue formation and its maintenance.