Abstract
Centrifugal serotonergic fibers innervate the olfactory bulb, but the importance of these projections for olfactory processing is unclear. We examined serotonergic modulation of sensory input to olfactory glomeruli using mice that express synaptopHluorin in olfactory receptor neurons (ORN). Odor-evoked synaptic input to glomeruli was attenuated by increased serotonin signaling through serotonin 2C (5-HT2C) receptors and amplified by decreased serotonergic activity. Intravital multiphoton calcium imaging revealed that 5-HT2C receptor activation amplified odor-evoked activity in a subset of juxtaglomerular cells and attenuated glutamate release from ORN terminals via GABA(B) receptors. Endogenous serotonin released by electrical stimulation of the dorsal raphe nucleus attenuated odor-evoked responses without detectable bias in glomerular position or odor identity. Weaker glomerular responses, however, were less sensitive to raphe stimulation than strong responses. Our data indicate that the serotonergic system regulates odor inputs in the olfactory bulb and suggest that behavioral states may alter odor processing at the earliest stages.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Calcium Signaling / physiology
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Cell Differentiation / physiology
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Efferent Pathways / cytology
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Efferent Pathways / growth & development
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Efferent Pathways / metabolism
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Glutamic Acid / metabolism
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Mice
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Mice, Transgenic
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism
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Olfactory Bulb / cytology
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Olfactory Bulb / growth & development*
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Olfactory Bulb / metabolism
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Olfactory Pathways / cytology
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Olfactory Pathways / growth & development*
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Olfactory Pathways / metabolism
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Olfactory Receptor Neurons / cytology
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Olfactory Receptor Neurons / growth & development*
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Olfactory Receptor Neurons / metabolism
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Raphe Nuclei / cytology
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Raphe Nuclei / growth & development*
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Raphe Nuclei / metabolism
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Receptor, Serotonin, 5-HT2C / metabolism
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Receptors, GABA-B / metabolism
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Sensory Receptor Cells / cytology
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Sensory Receptor Cells / metabolism
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Serotonin / physiology*
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Smell / physiology*
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Synapses / metabolism
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Synaptic Transmission / physiology
Substances
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Nerve Tissue Proteins
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Receptor, Serotonin, 5-HT2C
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Receptors, GABA-B
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synapto-pHluorin protein, mouse
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Serotonin
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Glutamic Acid