Fluorescent Labeling of Surface or Intracellular Antigens in Whole-Mounts

During the last century, before the advent of microtomes capable of producing thin, even sections, whole-mounts and thick sections were used to study the peripheral nervous system. Tissues were either viewed directly, if sufficiently thin, or further separated into layers by acid maceration (1 ). Initially, histochemical staining, particularly methylene blue (2 ), was applied to whole-mounts to characterize neuronal cell types, distributions, and innervation of various organs. In more recent times precise innervations were traced through the use of histochemical techniques specific for neuronal components. Histofluorescence techniques were introduced by Falk (3 ) for the localization of nonadrenaline-containing nerves, and the discovery of neuropeptides led to the application of immunohistochemical techniques in the late 1970s and early 1980s (4 ,5 ) Most recently, the application of monoclonal antibody technology has opened a new era in research and diagnosis such that in situ normal and pathological tissue constituents may be detected in whole-mounts ranging from tissues to entire organisms.