title: Mitral cells in the olfactory bulb are mainly excited through a multistep signaling path.
abstract: Within the olfactory system, information flow from the periphery onto output mitral cells (MCs) of the olfactory bulb (OB) has been thought to be mediated by direct synaptic inputs from olfactory sensory neurons (OSNs). Here, we performed patch-clamp measurements in rat and mouse OB slices to investigate mechanisms of OSN signaling onto MCs, including the assumption of a direct path, using electrical and optogenetic stimulation methods that selectively activated OSNs. We found that MCs are in fact not typically activated by direct OSN inputs and instead require a multistep, diffuse mechanism involving another glutamatergic cell type, the tufted cells. The preference for a multistep mechanism reflects the fact that signals arising from direct OSN inputs are drastically shunted by connexin 36-mediated gap junctions on MCs, but not tufted cells. An OB circuit with tufted cells intermediate between OSNs and MCs suggests that considerable processing of olfactory information occurs before its reaching MCs.
authors.affiliation: Neuroscience Program, Department of Physiology and Biophysics, University of Colorado, Denver, Anschutz Medical Campus, Aurora, Colorado 80045, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Gire
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Franks
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Zak
authors.forename: Kenji F
authors.initials: KF
authors.lastname: Tanaka
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Whitesell
authors.forename: Abigail A
authors.initials: AA
authors.lastname: Mulligan
authors.forename: René
authors.initials: R
authors.lastname: Hen
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Schoppa
mesh_terms: D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005260:Female; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009830:Olfactory Bulb / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*