title: Swimming against the tide: investigations of the C-bouton synapse.
abstract: C-boutons are important cholinergic modulatory loci for state-dependent alterations in motoneuron firing rate. m2 receptors are concentrated postsynaptic to C-boutons, and m2 receptor activation increases motoneuron excitability by reducing the action potential afterhyperpolarization. Here, using an intensive review of the current literature as well as data from our laboratory, we illustrate that C-bouton postsynaptic sites comprise a unique structural/functional domain containing appropriate cellular machinery (a "signaling ensemble") for cholinergic regulation of outward K(+) currents. Moreover, synaptic reorganization at these critical sites has been observed in a variety of pathologic states. Yet despite recent advances, there are still great challenges for understanding the role of C-bouton regulation and dysregulation in human health and disease. The development of new therapeutic interventions for devastating neurological conditions will rely on a complete understanding of the molecular mechanisms that underlie these complex synapses. Therefore, to close this review, we propose a comprehensive hypothetical mechanism for the cholinergic modification of α-MN excitability at C-bouton synapses, based on findings in several well-characterized neuronal systems.
authors.affiliation: Boonshoft School of Medicine, Department of Neuroscience, Cell Biology and Physiology, Wright State University Dayton, OH, USA.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Deardorff
authors.affiliation: Boonshoft School of Medicine, Department of Neuroscience, Cell Biology and Physiology, Wright State University Dayton, OH, USA.
authors.forename: Shannon H
authors.initials: SH
authors.lastname: Romer
authors.affiliation: Boonshoft School of Medicine, Department of Neuroscience, Cell Biology and Physiology, Wright State University Dayton, OH, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Sonner
authors.affiliation: Boonshoft School of Medicine, Department of Neuroscience, Cell Biology and Physiology, Wright State University Dayton, OH, USA.
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Fyffe
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D006801:Humans; D009046:Motor Neurons / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology*; D043585:Receptor, Muscarinic M2; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology*; D013550:Swimming / Q000502:physiology*; D013569:Synapses / Q000235:genetics / Q000502:physiology*; D050494:Vesicular Acetylcholine Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C406328:KCNN3 protein, human; D043585:Receptor, Muscarinic M2; D051640:Small-Conductance Calcium-Activated Potassium Channels; D050494:Vesicular Acetylcholine Transport Proteins
keywords: C-boutons; Kv2.1; SK; acetylcholine; afterhyperpolarization; subsurface cistern; α-motoneuron