AUTOMETALLOGRAPHIC LOCALIZATION OF SYNAPTIC VESICULAR ZINC AND LYSOSOMAL GOLD, SILVER, AND MERCURY

Autometallography (AMG) is a process by which nanometer sized gold particles and crystal lattices of sulfide or selenide of silver, mercury, or zinc encyst themselves in silver. This technique allows light and electron microscopy tracing of the metals in tissue sections from organisms that have been exposed to salts of silver, gold, or mercury. Because it is the crystal lattices that are silver encapsulated, the technique is extremely precise, but also very sensitive, as only a few atoms of gold or molecules of mercury selenide are necessary to initiate the AMG process. We report detailed protocols for AMG methods for each metal and ways of differentiating between them. The central nervous system contains a unique group of zinc enriched (ZEN) neurons, which enclose a specific pool of chelatable zinc in a portion of their synaptic vesicles. This zinc pool can be transformed either to zinc selenide crystal lattices by in vivo treatment with sodium selenide or to zinc sulfide crystal lattices after transcardiac perfusion with sodium sulfide. After AMG development of the crystals, a most detailed pattern created by ZEN terminals can be observed.