title: Rapid induction of granule cell elimination in the olfactory bulb by noxious stimulation in mice.
abstract: Elimination of granule cells (GCs) in the olfactory bulb (OB) is not a continuous event but is rather promoted during short time windows associated with the animal's behavior. We previously showed that apoptotic GC elimination is enhanced during food eating and subsequent rest or sleep, and that top-down inputs from the olfactory cortex (OC) to the OB during the postprandial period are the crucial signal promoting GC elimination. However, whether enhanced GC elimination occurs during behaviors other than postprandial behavior is not clear. Here, we investigated whether exposure to noxious stimulation promotes apoptotic GC elimination in mice. Mice were delivered a brief electrical foot shock, during and immediately after which they showed startle and fear responses. Surprisingly, the number of apoptotic GCs increased 2-fold within 10 min after the start of foot shock delivery. This enhancement of GC apoptosis was significantly suppressed by injection of the GABAA receptor agonist muscimol in the OC, despite these muscimol-injected mice showing similar behavioral responses by foot shock as control mice. These results indicate that GC elimination is promoted in foot shock-delivered mice within a short time period of startle and fear responses. They also indicate that OC activity plays a central role in the enhanced GC elimination during this period, as is also the case in GC elimination during the postprandial period.
authors.affiliation: Department of Physiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan; CREST, Japan Science and Technology Agency, Saitama, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Komano-Inoue
authors.affiliation: Department of Physiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan; CREST, Japan Science and Technology Agency, Saitama, Japan.
authors.forename: Koshi
authors.initials: K
authors.lastname: Murata
authors.affiliation: Department of Physiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan; CREST, Japan Science and Technology Agency, Saitama, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Mori
authors.affiliation: Department of Physiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan; CREST, Japan Science and Technology Agency, Saitama, Japan. Electronic address: yamaguti@m.u-tokyo.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D017209:Apoptosis; D002452:Cell Count; D004558:Electric Stimulation; D005239:Fear / Q000187:drug effects; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D007395:Interneurons / Q000187:drug effects / Q000473:pathology*; D008297:Male; D008810:Mice, Inbred C57BL; D009118:Muscimol / Q000494:pharmacology; D009830:Olfactory Bulb / Q000187:drug effects / Q000473:pathology*; D013216:Reflex, Startle / Q000187:drug effects; D013315:Stress, Psychological / Q000473:pathology* / Q000523:psychology
chemical_list: D058785:GABA-A Receptor Agonists; D009118:Muscimol
keywords: Apoptosis; Fear; Foot shock; Granule cell; Olfactory bulb; Olfactory cortex