Abstract
It is known that the median preoptic nucleus (POMe) sends dense projections to the subfornical organ (SFO). However, the functional significance of these projections have not been well discussed. In this electron microscopic study, we investigated the presence of synapses between POMe-derived axon terminals and SFO neurons that project to the paraventricular hypothalamic nucleus (PVN). After injection of a retrograde tracer, wheat germ agglutinin-conjugated horseradish peroxidase–colloidal gold complex, into the PVN, many labeled neurons were found in the SFO. In contrast, after injection of an anterograde tracer, biotinylated dextran amine, in the POMe, abundant labeled axon varicosities were observed in the SFO. Using electron microscopy, synapses were identified between retrogradely labeled dendrites and cell bodies, and anterogradely labeled axon terminals, indicating that POMe neurons innervate SFO neurons projecting to the PVN. The possibility that POMe neurons play multiple roles in the neuronal circuit responsible for vasopressin release and/or cardiovascular regulation is also discussed.
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Acknowledgements
The author thanks Ms Yuko Honda for her technical assistance. I would also like to thank Editage (http://www.editage.jp) for English language editing.
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H. K. contributed to all parts of this study, including the conception and design of the experiments, operation and fixation of the animals, preparation of light and electron microscopic sections, observation and collection of the data, interpretation and analysis of the data, and writing of the manuscript.
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Kawano, H. Synaptic contact between median preoptic neurons and subfornical organ neurons projecting to the paraventricular hypothalamic nucleus. Exp Brain Res 235, 1053–1062 (2017). https://doi.org/10.1007/s00221-016-4862-7
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DOI: https://doi.org/10.1007/s00221-016-4862-7