[Zinc-iodine-osmium impregnation of giant synaptosomes obtained from the hippocampal formation of the rabbit].

The fraction of giant synaptosomes from the r. inferior of the rabbit hippocampus was studied using impregnation with zinc iodide-osmium tetroxide (XIO) reagent and electron microscopy. In this fraction, light and dark synaptosomes were observed. The reaction product was found in the clear-centered synaptic vesicles (200-400 A) as electron-dense structures of different forms and small osmiophilic particles on the vesicular membranes. Dense-cored vesicles and postsynaptic structures were not revealed with ZIO-reagent. The structures revealed with ZIO-reagent in the giant synaptosomes of the hippocampus are supposedly related to stroage of the neurotransmitter-glutamate.