title: Optogenetic Activation of Dorsal Raphe Serotonin Neurons Rapidly Inhibits Spontaneous But Not Odor-Evoked Activity in Olfactory Cortex.
abstract: Serotonin (5-hydroxytriptamine; 5-HT) is implicated in a variety of brain functions including not only the regulation of mood and control of behavior but also the modulation of perception. 5-HT neurons in the dorsal raphe nucleus (DRN) often fire locked to sensory stimuli, but little is known about how 5-HT affects sensory processing, especially on this timescale. Here, we used an optogenetic approach to study the effect of 5-HT on single-unit activity in the mouse primary olfactory (anterior piriform) cortex. We show that activation of DRN 5-HT neurons rapidly inhibits the spontaneous firing of olfactory cortical neurons, acting in a divisive manner, but entirely spares sensory-driven firing. These results identify a new role for serotonergic modulation in dynamically regulating the balance between different sources of neural activity in sensory systems, suggesting a possible role for 5-HT in perceptual inference.
  
  
  CONCLUSIONS
  Serotonin is implicated in a wide variety of (pato)physiological functions including perception, but its precise role has remained elusive. Here, using optogenetic tools in vivo, we show that serotonergic neuromodulation prominently inhibits the spontaneous electrical activity of neurons in the primary olfactory cortex on a rapid (<1 s) timescale but leaves sensory responses unaffected. These results identify a new role for serotonergic modulation in rapidly changing the balance between different sources of neural activity in sensory systems.
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, 1400-038, Lisbon, Portugal.
authors.forename: Eran
authors.initials: E
authors.lastname: Lottem
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, 1400-038, Lisbon, Portugal, Research Group for Cellular and Network Neurophysiology of the Hungarian Academy of Sciences, Department of Physiology, Anatomy, and Neuroscience, and Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, 6726, Szeged, Hungary mlorincz@bio.u-szeged.hu zmainen@neuro.fchampalimaud.org.
authors.forename: Magor L
authors.identifier: http://orcid.org/0000-0001-5240-1904
authors.initials: ML
authors.lastname: Lörincz
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, 1400-038, Lisbon, Portugal, mlorincz@bio.u-szeged.hu zmainen@neuro.fchampalimaud.org.
authors.forename: Zachary F
authors.initials: ZF
authors.lastname: Mainen
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D008297:Male; D051379:Mice; D009415:Nerve Net / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D009812:Odorants; D066194:Olfactory Cortex / Q000166:cytology / Q000502:physiology*; D062308:Optogenetics / Q000379:methods; D011903:Raphe Nuclei / Q000502:physiology*; D059326:Serotonergic Neurons / Q000502:physiology*; D012903:Smell / Q000502:physiology*
keywords: feed-forward; feedback; inhibition; neuromodulation; odor