Polysialic acid regulates sympathetic outflow by facilitating information transfer within the nucleus of the solitary tract

Phillip Bokiniec, Shila Shahbazian, Stuart J. McDougall, Britt A. Berning, Delfine Cheng, Ida J. Llewellyn-Smith, Peter G.R. Burke, Simon McMullan, Martina Mühlenhoff, Herbert Hildebrandt, Filip Braet, Mark Connor, Nicolle H. Packer, Ann K. Goodchild

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    Abstract

    Expression of the large extracellular glycan, polysialic acid (polySia), is restricted in the adult, to brain regions exhibiting high levels of plasticity or remodeling, including the hippocampus, prefrontal cortex, and the nucleus of the solitary tract (NTS). The NTS, located in the dorsal brainstem, receives constant viscerosensory afferent traffic as well as input from central regions controlling sympathetic nerve activity, respiration, gastrointestinal functions, hormonal release, and behavior. Our aims were to determine the ultrastructural location of polySia in the NTS and the functional effects of enzymatic removal of polySia, both in vitro and in vivo. polySia immunoreactivity was found throughout the adult rat NTS. Electron microscopy demonstrated polySia at sites that influence neurotransmission: the extracellular space, fine astrocytic processes, and neuronal terminals. Removing polySia from the NTS had functional consequences. Whole-cell electrophysiological recordings revealed altered intrinsic membrane properties, enhancing voltage-gated K+ currents and increasing intracellular Ca2+. Viscerosensory afferent processing was also disrupted, dampening low-frequency excitatory input and potentiating high-frequency sustained currents at second-order neurons. Removal of polySia in the NTS of anesthetized rats increased sympathetic nerve activity, whereas functionally related enzymes that do not alter polySia expression had little effect. These data indicate that polySia is required for the normal transmission of information through the NTS and that changes in its expression alter sympathetic outflow. polySia is abundant in multiple but discrete brain regions, including sensory nuclei, in both the adult rat and human, where it may regulate neuronal function by mechanisms identified here.

    Original languageEnglish
    Pages (from-to)6558-6574
    Number of pages17
    JournalJournal of Neuroscience
    Volume37
    Issue number27
    DOIs
    Publication statusPublished - 5 Jul 2017

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    Keywords

    • Electron microscopy
    • Nucleus of the solitary tract
    • Patch clamp
    • Polysialic acid
    • Sympathetic nerve activity
    • Viscerosensory afferents

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  • Cite this

    Bokiniec, P., Shahbazian, S., McDougall, S. J., Berning, B. A., Cheng, D., Llewellyn-Smith, I. J., Burke, P. G. R., McMullan, S., Mühlenhoff, M., Hildebrandt, H., Braet, F., Connor, M., Packer, N. H., & Goodchild, A. K. (2017). Polysialic acid regulates sympathetic outflow by facilitating information transfer within the nucleus of the solitary tract. Journal of Neuroscience, 37(27), 6558-6574. https://doi.org/10.1523/JNEUROSCI.0200-17.2017