title: The zinc iodide-osmium tetroxide (ZIO) reaction on nerve endings in the median eminence of the rat under normal and experimental conditions.
abstract: The reaction of nerve endings in the median eminence of the rat to zinc iodide-osmium tetroxide (ZIO) staining was examined electron microscopically under normal and experimental conditions. The experimental condition of catecholamine exhaustion in the nerve endings was induced by the administration of H44/68 and reserpine. Vesicles in the terminals of catecholaminergic nerves reacted similarly to ZIO staining in both normal and experimental material. The majority of synaptic vesicles in various terminals gave a positive ZIO reaction. The neurosecretory elementary granules, however, failed to react with ZIO. On the other hand, some nerve terminals in the external layer of the median eminence showed a strong positive reaction in the cytoplasmic matrix, in mitochondria as well as in synaptic vesicles. These findings strongly suggest that the ZIO-positive substance in nerve terminals is not the transmitter itself, i.e. the monoamine, but rather represents a range of substances commonly found in various kinds of synaptic vesicles and is probably proteinaceous in nature. A brief discussion is also given on the difference in ZIO reactivity between neurosecretory elementary granules and small vesicles in the hypothalamo-hypophyseal tract.
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000032:analysis; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000648:ultrastructure*; D007454:Iodides; D008297:Male; D008473:Median Eminence / Q000032:analysis / Q000648:ultrastructure*; D008781:Methyltyrosines / Q000494:pharmacology; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009411:Nerve Endings / Q000032:analysis / Q000648:ultrastructure*; D009419:Nerve Tissue Proteins / Q000032:analysis; D009992:Osmium; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D013194:Staining and Labeling; D015032:Zinc
chemical_list: D002395:Catecholamines; D007454:Iodides; D008781:Methyltyrosines; D009419:Nerve Tissue Proteins; D009992:Osmium; D012110:Reserpine; D015032:Zinc