title: Perisomatic-targeting granule cells in the mouse olfactory bulb.
abstract: Inhibitory interneurons in the hippocampus and neocortex are differentiated into several morphological and functional subtypes that innervate distinct subcellular domains of principal neurons. In the olfactory bulb (OB), odor information is processed by local neuronal circuits that include the major inhibitory interneuron, granule cells (GCs). All GCs reported to date target their inhibitory output synapses mainly to dendrites of mitral cells (MCs) and tufted cells (TCs) in the external plexiform layer (EPL). Here we identified a novel type of GC that targets output synapses selectively to the perisomatic region of MCs. In the OB of adult transgenic mice expressing green fluorescent protein (GFP) under the control of nestin gene regulatory regions, we observed cells in the granule cell layer (GCL) that have GC-like morphology and strongly express GFP (referred to as type S cells). Type S cells expressed NeuN and GAD67, molecular markers for GCs. Intracellular labeling of type S cells revealed that their dendrites did not enter the EPL, but formed branches and spines within the GCL, internal plexiform layer, and mitral cell layer. Type S cells typically had huge spines at the ends of the apical dendrites. Some of the terminal spines attached to the perisomatic region of MCs and formed dendrosomatic reciprocal synapses with a presumed granule-to-mitral inhibitory synapse and a mitral-to-granule excitatory synapse. These findings indicate the morphological differentiation of GCs into dendritic-targeting and perisomatic-targeting subsets, and suggest the functional differentiation of the GC subsets in the processing of odor information in the OB.
authors.affiliation: Department of Physiology, University of Tokyo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Naritsuka
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Sakai
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hashikawa
authors.forename: Kensaku
authors.initials: K
authors.lastname: Mori
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D000089622:Doublecortin Domain Proteins; D005968:Glutamate Decarboxylase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism; D007395:Interneurons / Q000145:classification* / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron / Q000379:methods; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D064231:Nestin; D009479:Neuropeptides / Q000378:metabolism; D009830:Olfactory Bulb / Q000166:cytology*; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D043222:Ubiquitin Thiolesterase / Q000378:metabolism
chemical_list: D000089622:Doublecortin Domain Proteins; D007381:Intermediate Filament Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; D064231:Nestin; D009479:Neuropeptides; D049452:Green Fluorescent Proteins; D043222:Ubiquitin Thiolesterase; C496976:Uchl1 protein, mouse; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1