title: When are new hippocampal neurons, born in the adult brain, integrated into the network that processes spatial information?
abstract: Adult-born neurons in the dentate gyrus (DG) functionally integrate into the behaviorally relevant hippocampal networks, showing a specific Arc-expression response to spatial exploration when mature. However, it is not clear when, during the 4- to 6-week interval that is critical for survival and maturation of these neurons, this specific response develops. Therefore, we characterized Arc expression after spatial exploration or cage control conditions in adult-born neurons from rats that were injected with BrdU on one day and were sacrificed 1, 7, 15, 30, and 45 days post-BrdU injection (PBI). Triple immunostaining for NeuN, Arc, and BrdU was analyzed through the different DG layers. Arc protein expression in BrdU-positive cells was observed from day 1 to day 15 PBI but was not related to behavioral stimulation. The specific Arc-expression response to spatial exploration was observed from day 30 and 45 in about 5% of the BrdU-positive cell population. Most of the BrdU-positive neurons expressing Arc in response to spatial exploration (∼90%) were located in DG layer 1, and no Arc expression was observed in cells located in the subgranular zone (SGZ). Using the current data and that obtained previously, we propose a mathematical model suggesting that new neurons are unlikely to respond to exploration by expressing Arc after they are 301 days old, and also that in a 7-month-old rat the majority (60%) of the neurons that respond to exploration must have been born during adulthood; thus, suggesting that adult neurogenesis in the DG is highly relevant for spatial information processing.
authors.affiliation: Laboratorio de redes neuronales plásticas, Departamento de Neurobiología Conductual y Cognitiva, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro Qro, México.
authors.forename: C Jimena
authors.initials: CJ
authors.lastname: Sandoval
authors.forename: Marisela
authors.initials: M
authors.lastname: Martínez-Claros
authors.forename: Paola C
authors.initials: PC
authors.lastname: Bello-Medina
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Pérez
authors.forename: Víctor
authors.initials: V
authors.lastname: Ramírez-Amaya
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002465:Cell Movement; D002470:Cell Survival; D018891:Dentate Gyrus / Q000166:cytology; D006624:Hippocampus / Q000166:cytology*; D008136:Longevity / Q000502:physiology; D008297:Male; D008954:Models, Biological; D009415:Nerve Net / Q000166:cytology*; D009474:Neurons / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors
chemical_list: D001973:Bromodeoxyuridine