Abstract
Many rodents explore their environment by rhythmically palpating objects with their mystacial whiskers. These rhythmic whisker movements ("whisking"; 5-9 Hz) are thought to be regulated by an unknown brainstem central pattern generator (CPG). We tested the hypothesis that serotonin (5-HT) inputs to whisking facial motoneurons (wFMNs) are part of this CPG. In response to exogenous serotonin, wFMNs recorded in vitro fire rhythmically at whisking frequencies, and selective 5-HT2 or 5-HT3 receptor antagonists suppress this rhythmic firing. In vivo, stimulation of brainstem serotonergic raphe nuclei evokes whisker movements. Unilateral infusion of selective 5-HT2 or 5-HT3 receptor antagonists suppresses ipsilateral whisking and substantially alters the frequencies and symmetry of whisker movements. These findings suggest that serotonin is both necessary and sufficient to generate rhythmic whisker movements and that serotonergic premotoneurons are part of a whisking CPG.
Publication types
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Comparative Study
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Animals, Newborn
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Brain Stem / anatomy & histology
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Brain Stem / drug effects
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Brain Stem / physiology*
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Bridged Bicyclo Compounds, Heterocyclic / pharmacology
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Electric Stimulation
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Electromyography / methods
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Immunohistochemistry
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In Vitro Techniques
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Lysine / analogs & derivatives*
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Lysine / metabolism
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Male
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Metergoline / pharmacology
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Microdialysis
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Motor Neurons / drug effects
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Motor Neurons / physiology*
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Movement / drug effects
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Movement / physiology
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Oxazines / pharmacology
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Patch-Clamp Techniques / methods
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Rats
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Rats, Sprague-Dawley
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Serotonin / physiology*
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Serotonin Antagonists / pharmacology
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Statistics as Topic
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Vibrissae / drug effects
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Vibrissae / innervation
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Vibrissae / physiology*
Substances
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Bridged Bicyclo Compounds, Heterocyclic
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Oxazines
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Serotonin Antagonists
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Metergoline
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Serotonin
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azasetron
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biocytin
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Lysine