title: Postsynaptic muscarinic m2 receptors at cholinergic and glutamatergic synapses of mouse brainstem motoneurons.
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.
authors.affiliation: Université Paris Descartes, 75006 Paris, France. zsolt.csaba@inserm.fr
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Csaba
authors.forename: Eric
authors.initials: E
authors.lastname: Krejci
authors.forename: Véronique
authors.initials: V
authors.lastname: Bernard
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000166:cytology*; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D016253:Microscopy, Immunoelectron; D009046:Motor Neurons / Q000166:cytology*; D043585:Receptor, Muscarinic M2 / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism* / Q000648:ultrastructure; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D043585:Receptor, Muscarinic M2; C493461:Slc18a3 protein, rat; D050494:Vesicular Acetylcholine Transport Proteins; D050598:Vesicular Glutamate Transport Protein 1