Electron microscopical localization of the zinc in hippocampal mossy fibre synapses by a modified sulfide silver procedure.

Abstract

The sulfide silver method of Timm demonstrates the distribution of heavy metals in brain and other tissues. The method is unspecific, but in the hippocampal region is known to visualize the zinc concentrated in the mossy fibre system. In this study, the method was modified, including the use of formaldehyde as a fixative, to give a tolerable degree of ultrastructural preservation. Electrondense silver particles were demonstrated within mossy fibre giant boutons exclusively. They were evenly distributed throughout the boutons but avoided the mitochondria entirely. No concentration close to synaptic clefts or cell membranes elsewhere was observed. The postsynaptic elements (ramified spines or excrescences) were devoid of silver particles.