Postsynaptic muscarinic m2 receptors at cholinergic and glutamatergic synapses of mouse brainstem motoneurons

Authors

  • Zsolt Csaba,

    Corresponding author
    1. Université Paris Descartes, 75006 Paris, France
    2. Institut National de la Santé et la Recherche Médicale (INSERM), U686, 75006 Paris, France
    3. Institut National de la Santé et la Recherche Médicale (INSERM), U676, 75019 Paris, France
    4. Université Paris Diderot, Sorbonne Paris Cité, UMR676, 75019 Paris, France
    • INSERM U676, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
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  • Eric Krejci,

    1. Université Paris Descartes, 75006 Paris, France
    2. Institut National de la Santé et la Recherche Médicale (INSERM), U686, 75006 Paris, France
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  • Véronique Bernard

    1. Université Paris Descartes, 75006 Paris, France
    2. Institut National de la Santé et la Recherche Médicale (INSERM), U686, 75006 Paris, France
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Abstract

In many brain areas, few cholinergic synapses are identified. Acetylcholine is released into the extracellular space and acts through diffuse transmission. Motoneurons, however, are contacted by numerous cholinergic terminals, indicating synaptic cholinergic transmission on them. The muscarinic m2 receptor is the major acetylcholine receptor subtype of motoneurons; therefore, we analyzed the localization of the m2 receptor in correlation with synapses by electron microscopic immunohistochemistry in the mouse trigeminal, facial, and hypoglossal motor nuclei. In all nuclei, m2 receptors were localized at the membrane of motoneuronal perikarya and dendrites. The m2 receptors were concentrated at cholinergic synapses located on the perikarya and most proximal dendrites. However, m2 receptors at cholinergic synapses represented only a minority (<10%) of surface m2 receptors. The m2 receptors were also enriched at glutamatergic synapses in both motoneuronal perikarya and dendrites. A relatively large proportion (20–30%) of plasma membrane–associated m2 receptors were located at glutamatergic synapses. In conclusion, the effect of acetylcholine on motoneuron populations might be mediated through a synaptic as well as diffuse type of transmission. J. Comp. Neurol. 521:2008–2024, 2013. © 2012 Wiley Periodicals, Inc.

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