title: Odour enrichment increases adult-born dopaminergic neurons in the mouse olfactory bulb.
abstract: The olfactory bulb (OB) is the first brain region involved in the processing of olfactory information. In adult mice, the OB is highly plastic, undergoing cellular/molecular dynamic changes that are modulated by sensory experience. Odour deprivation induces down-regulation of tyrosine hydroxylase (TH) expression in OB dopaminergic interneurons located in the glomerular layer (GL), resulting in decreased dopamine in the OB. Although the effect of sensory deprivation is well established, little is known about the influence of odour enrichment on dopaminergic cells. Here we report that prolonged odour enrichment on C57BL/6J strain mice selectively increases TH-immunopositive cells in the GL by nearly 20%. Following odour enrichment on TH-green fluorescent protein (GFP) transgenic mice, in which GFP identified both mature TH-positive cells and putative immature dopaminergic cells expressing TH mRNA but not TH protein, we found a similar 20% increase in GFP-expressing cells, with no changes in the ratio between TH-positive and TH-negative cells. These data suggest that enriched conditions induce an expansion in the whole dopaminergic lineage. Accordingly, by using 5-bromo-2-deoxyuridine injections to label adult-generated cells in the GL of TH-GFP mice, we found an increase in the percentage of 5-bromo-2-deoxyuridine-positive dopaminergic cells in enriched compared with control conditions, whereas no differences were found for calretinin- and calbindin-positive subtypes. Strikingly, the fraction of newborn cells among the dopaminergic population doubled in enriched conditions. On the whole, our results demonstrate that odour enrichment drives increased integration of adult-generated dopaminergic cells that could be critical to adapt the OB circuits to the environmental incoming information.
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Via Accademia Albertina 13, 10123, Torino, Italy; Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bonzano
authors.forename: Serena
authors.initials: S
authors.lastname: Bovetti
authors.forename: Aldo
authors.initials: A
authors.lastname: Fasolo
authors.forename: Paolo
authors.initials: P
authors.lastname: Peretto
authors.forename: Silvia
authors.initials: S
authors.lastname: De Marchis
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine; D064032:Calbindin 2 / Q000378:metabolism; D064026:Calbindins / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006799:Housing, Animal; D008297:Male; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055495:Neurogenesis / Q000502:physiology; D009812:Odorants; D009830:Olfactory Bulb / Q000502:physiology*; D010812:Physical Stimulation; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D012903:Smell / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
chemical_list: C576511:Calb2 protein, mouse; D064032:Calbindin 2; D064026:Calbindins; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins; D014446:Tyrosine 3-Monooxygenase; D001973:Bromodeoxyuridine
keywords: 5-bromo-2-deoxyuridine; adult neurogenesis; inhibitory interneurons; tyrosine hydroxylase