Summary
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.
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This work was supported in part by a research grant from the Ministry of Education, Japan
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Matsuura, T., Ibata, Y. & Sano, Y. The zinc iodide-osmium tetroxide (ZIO) reaction on nerve endings in the median eminence of the rat under normal and experimental conditions. Cell Tissue Res. 173, 279–286 (1976). https://doi.org/10.1007/BF00220316
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DOI: https://doi.org/10.1007/BF00220316