Light and electron microscopic identification of monoaminergic terminals in the central nervous system

A brief critical survey of methods used for light and electron microscopic examination of amine-containing pathways within the CNS. Light microscopic techniques such as fluorescence histochemistry, immunocytochemistry, autoradiography, silver degeneration techniques, and retrograde tracing technique are suitable for studying the topography of pathways but, due to limits of resolution, they are inadequate for identifying terminals. Electron microscopy which is adequate to visualize terminals does not provide an overall view. This review considers various methods which have been devised to specifically detect aminergic nerve terminals. Electrolytic and chemical induced degenerations are described in noradrenergic, dopaminergic, and serotoninergic terminals. Although the individual degenerative alterations are not specific for aminergic terminals, the degenerative process when considered as a whole can be informative. At present no single technique can provide complete information about the origin, course, connections, and terminals of aminergic systems. Concurrent application of light and electron microscopy, experimental surgery, histochemistry, and microsample biochemistry would provide a complete description.