A Modified Silver Technique (de Olmos Stain) for Assessment of Neuronal and Axonal Degeneration

Silver impregnation histological techniques yield excellent visualization of degenerating neurons and their processes in animal models of neurological diseases. These methods also provide a particularly valuable complement to current immunocytochemical techniques for recognition of axon injury in the setting of brain or spinal cord trauma, ischemia, or neurodegenerative diseases. Despite their utility, silver methods are not commonly used because of complex preparation requirements and inconsistent results obtained by inexperienced histologists. This chapter details a modification of the de Olmos amino-cupric-silver protocol, which has been adapted for efficient processing of large numbers of mouse or rat brains. One author (T.I.T.) has used this method for several years to identify degenerating neurons in adult and neonatal rodent brains. A detailed protocol is provided, with attention to the most critical variables in tissue fixation and solution preparation. Examples are shown of axon injury in the rat brain after focal ischemia.