201
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Guérin D, Sacquet J, Mandairon N, Jourdan F, Didier A. Early locus coeruleus degeneration and olfactory dysfunctions in Tg2576 mice. Neurobiol Aging 2007; 30:272-83. [PMID: 17618708 DOI: 10.1016/j.neurobiolaging.2007.05.020] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 05/21/2007] [Accepted: 05/24/2007] [Indexed: 02/01/2023]
Abstract
Olfactory deficiency has been reported in the early stages of Alzheimer's disease (AD) in humans but is very poorly understood due to the lack of investigations in animal models of AD. Recent studies point to the noradrenergic system as an important target of the AD pathological process. In addition, noradrenalin has been shown to influence adult neurogenesis which is implicated in cognitive functions. We have therefore investigated the olfactory neurogenesis and cognitive performances in young transgenic Tg2576 mice in relation with the status of the noradrenergic and the cholinergic systems. Tg2576 showed a deficit in neurogenesis in the olfactory bulb evidenced by an increased death of newborn cells and a reduced expression of PSA-NCAM. The locus coeruleus degenerated in Tg2576 between the age of 6.5 and 8 months. These changes were associated with olfactory memory impairments. Our findings indicate that a noradrenergic deficiency could play a role in the early stages of the pathological process in this transgenic model and induce olfactory cognitive impairments through an alteration of olfactory neurogenesis.
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Affiliation(s)
- Delphine Guérin
- Laboratoire de Neuroscience et Systèmes Sensoriels, Université de Lyon, F-69007 Lyon, France
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202
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Tashiro A, Makino H, Gage FH. Experience-specific functional modification of the dentate gyrus through adult neurogenesis: a critical period during an immature stage. J Neurosci 2007; 27:3252-9. [PMID: 17376985 PMCID: PMC6672473 DOI: 10.1523/jneurosci.4941-06.2007] [Citation(s) in RCA: 386] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neural circuits in the dentate gyrus are continuously modified by adult neurogenesis, whose level is affected by the animal's experience. However, it is not known whether this experience-dependent anatomical modification alters the functional properties of the dentate gyrus. Here, using the expression of immediate early gene products, c-fos and Zif268, as indicators of recently activated neurons, we show that previous exposure to an enriched environment increases the total number of new neurons and the number of new neurons responding to reexposure to the same environment. The increase in the density of activated new neurons occurred specifically in response to exposure to the same environment but not to a different experience. Furthermore, we found that these experience-specific modifications are affected exclusively by previous exposure around the second week after neuronal birth but not later than 3 weeks. Thus, the animal's experience within a critical period during an immature stage of new neurons determines the survival and population response of the new neurons and may affect later neural representation of the experience in the dentate gyrus. This experience-specific functional modification through adult neurogenesis could be a mechanism by which new neurons exert a long-term influence on the function of the dentate gyrus related to learning and memory.
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Affiliation(s)
- Ayumu Tashiro
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California 92037
| | - Hiroshi Makino
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California 92037
| | - Fred H. Gage
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California 92037
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203
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Mandairon N, Sacquet J, Garcia S, Ravel N, Jourdan F, Didier A. Neurogenic correlates of an olfactory discrimination task in the adult olfactory bulb. Eur J Neurosci 2006; 24:3578-88. [PMID: 17229106 DOI: 10.1111/j.1460-9568.2006.05235.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In the main olfactory bulb, stimuli are coded within the spatio-temporal pattern of mitral cells' activity. Granule cells are interneurons that shape the mitral cells' activity, and are continuously generated in the adult main olfactory bulb. However, the role of granule cell renewal remains elusive. We show here that an associative olfactory discrimination task reduces the survival of newborn neurons. However, when the olfactory task involves perceptually related odorants, the learning process is slower and does not induce such a reduction in the number of new neurons. Mapping newborn cells within the granule cell layer of the main olfactory bulb reveals a clustered distribution that evolves with learning as a function of odorant similarity and partly overlaps with the immediate-early gene Zif268 expression pattern. These data provide insight into the functional mechanisms underlying olfactory discrimination learning, and promote the importance of neurogenesis as a cellular basis for the restructuring of odor images in the main olfactory bulb.
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Affiliation(s)
- Nathalie Mandairon
- Laboratoire de Neurosciences et Systèmes Sensoriels, CNRS UMR 5020, Université Claude Bernard Lyon1, 50 avenue Tony Garnier, 69366, LYON cedex 07, France.
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204
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Alonso M, Viollet C, Gabellec MM, Meas-Yedid V, Olivo-Marin JC, Lledo PM. Olfactory discrimination learning increases the survival of adult-born neurons in the olfactory bulb. J Neurosci 2006; 26:10508-13. [PMID: 17035535 PMCID: PMC6674694 DOI: 10.1523/jneurosci.2633-06.2006] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the olfactory bulb (OB), new neurons are added throughout life, forming an integral part of the functioning circuit. Yet only some of them survive more than a month. To determine whether this turnover depends on olfactory learning, we examined the survival of adult newborn cells labeled with the cell division marker BrdU, administered before learning in an olfactory discrimination task. We report that discrimination learning increases the number of newborn neurons in the adult OB by prolonging their survival. Simple exposure to the pair of olfactory cues did not alter neurogenesis, indicating that the mere activation of sensory inputs during the learning task was insufficient to alter neurogenesis. The increase in cell survival after learning was not uniformly distributed throughout angular sectors of coronal sections of the OB. Monitoring odor activation maps using patterns of Zif268 immediate early gene expression revealed that survival was greater in regions more activated by the non-reinforced odorant. We conclude that sensory activation in a learning context not only controls the total number of newborn neurons in the adult OB, but also refines their precise location. Shaping the distribution of newborn neurons by influencing their survival could optimize the olfactory information processing required for odor discrimination.
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Affiliation(s)
- Mariana Alonso
- Perception and Memory Laboratory, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2182, and
| | - Cécile Viollet
- Perception and Memory Laboratory, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2182, and
| | - Marie-Madeleine Gabellec
- Perception and Memory Laboratory, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2182, and
| | - Vannary Meas-Yedid
- Quantitative Image Analysis Unit, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2582, Pasteur Institute, 75724 Paris Cedex 15, France
| | - Jean-Christophe Olivo-Marin
- Quantitative Image Analysis Unit, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2582, Pasteur Institute, 75724 Paris Cedex 15, France
| | - Pierre-Marie Lledo
- Perception and Memory Laboratory, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2182, and
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205
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de Chevigny A, Lemasson M, Saghatelyan A, Sibbe M, Schachner M, Lledo PM. Delayed onset of odor detection in neonatal mice lacking tenascin-C. Mol Cell Neurosci 2006; 32:174-86. [PMID: 16730455 DOI: 10.1016/j.mcn.2006.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 03/23/2006] [Accepted: 04/06/2006] [Indexed: 10/24/2022] Open
Abstract
The olfactory bulb is one of the few regions in the adult mammalian forebrain in which neurons are constitutively replaced throughout life. New neurons generated in the subventricular zone migrate long distances along the rostral migratory stream to the olfactory bulb where they differentiate into interneurons. Neuronal precursor generation, migration and incorporation into the bulbar network occur in an environment rich in extracellular matrix molecules. We investigated the potential role of one of the constituents of the extracellular matrix, tenascin-C (TNC), in bulbar neurogenesis and olfactory performance using TNC-deficient mice. We found that TNC deficiency resulted in a delayed onset of olfactory responses in neonatal animals. This delay normalized at around postnatal day 10. Interestingly, this delay in early olfactory performance was not due to impaired bulbar neurogenesis as proliferation, migration, incorporation and fate determination of newborn bulbar interneurons were normal in TNC-deficient animals. Thus, we conclude that a constitutive lack of TNC does not affect bulbar neurogenesis, but instead leads to ontogenetically early impairments in olfactory detection.
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Affiliation(s)
- Antoine de Chevigny
- Laboratory of Perception and Memory, CNRS URA 2182, Pasteur Institute, 25 rue du Dr. Roux, 75015 Paris Cedex, France
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206
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Karten YJG, Jones MA, Jeurling SI, Cameron HA. GABAergic signaling in young granule cells in the adult rat and mouse dentate gyrus. Hippocampus 2006; 16:312-20. [PMID: 16435314 DOI: 10.1002/hipo.20165] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Throughout most of the developing brain, including the hippocampus, GABAergic synapses are the first to become functional. Several features of GABAergic signaling change across development, suggesting that this signaling in the immature brain may play important roles in the growth of young neurons and the establishment of networks. To determine whether GABA(A) receptor (GABA(A)R)-containing synapses in new neurons born in the adult dentate gyrus have similar immature features, we examined spontaneous and evoked GABA(A)R-mediated synaptic currents in young (POMC-EGFP or doublecortin-immunostained) granule cells in acute slice preparations from adult mice and rats. Spontaneous inhibitory postsynaptic currents (IPSCs) were observed in nearly all immature granule cells, but their frequency was considerably lower and their decay time constant was nearly two times longer than in neighboring mature (doublecortin-non-immunoreactive or EGFP-non-expressing) granule cells within the sub-granular zone. Evoked IPSCs (eIPSCs) in mature granule cells, but not immature granule cells, were sensitive to zolpidem, suggesting a maturational increase in GABA(A)R alpha1-subunit expression. Perforated-patch recording revealed that eIPSCs depolarized young neurons, but hyperpolarized mature neurons. The early establishment of synaptic GABAergic inputs slow IPSC decay time, and depolarizing action of eIPSCs are remarkably similar to features previously seen in neurons during development, suggesting that they are intrinsic features of immature neurons and not functions of the surrounding circuitry. These developmental features in adult-born granule cells could play a role in maturational processes such as developmental cell death. However, treatment of adult mice with GABA(A)R agonists and an inverse agonist did not significantly alter the number of 4- to 14-day-old BrdU-labeled cells.
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Affiliation(s)
- Yashmin J G Karten
- Unit on Neuroplasticity, NIH, MSC 3718, Bethesda, Maryland 20892-3718, USA
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207
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Lledo PM, Alonso M, Grubb MS. Adult neurogenesis and functional plasticity in neuronal circuits. Nat Rev Neurosci 2006; 7:179-93. [PMID: 16495940 DOI: 10.1038/nrn1867] [Citation(s) in RCA: 1017] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The adult brain is a plastic place. To ensure that the mature nervous system's control of behaviour is flexible in the face of a varying environment, morphological and physiological changes are possible at many levels, including that of the entire cell. In two areas of the adult brain - the olfactory bulb and the dentate gyrus - new neurons are generated throughout life and form an integral part of the normal functional circuitry. This process is not fixed, but highly modulated, revealing a plastic mechanism by which the brain's performance can be optimized for a given environment. The functional benefits of this whole-cell plasticity, however, remain a matter for debate.
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Affiliation(s)
- Pierre-Marie Lledo
- Laboratory of Perception and Memory, Institut Pasteur, Centre National de la Recherche Scientifique Unit de Recherche Associée 2182, 25, rue du Docteur Roux, 75724 Paris cedex 15, France.
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208
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Sasaki T, Kitagawa K, Yagita Y, Sugiura S, Omura-Matsuoka E, Tanaka S, Matsushita K, Okano H, Tsujimoto Y, Hori M. Bcl2 enhances survival of newborn neurons in the normal and ischemic hippocampus. J Neurosci Res 2006; 84:1187-96. [PMID: 16941650 DOI: 10.1002/jnr.21036] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neuronal progenitors in the adult hippocampus continually proliferate and differentiate to the neuronal lineage, and ischemic insult promotes hippocampal neurogenesis. However, newborn neurons show a progressive reduction in numbers during the initial few weeks, therefore, enhanced survival of newborn neurons seems to be essential for therapeutic strategy. Bcl-2 is a crucial regulator of programmed cell death in CNS development and in apoptotic and necrotic cell death. Therefore, we tested whether Bcl-2 overexpression enhances survival of newborn neurons in the adult mouse hippocampus under normal and ischemic conditions. Many newborn neurons in the hippocampal dentate gyrus undergo apoptosis. Human Bcl-2 expression in NSE-bcl-2 transgenic mice began at the immature neuronal stage and remained constant in surviving mature neurons. Bcl-2 significantly increased survival of newborn neurons under both conditions, but particularly after ischemia, with decreased cell death of newborn neurons in NSE-bcl-2 transgenic mice. We also clarified the effect by Bcl-2 overexpression of enhanced survival of newborn neurons in primary hippocampal cultures with BrdU labeling. These findings suggest that Bcl-2 plays a crucial role in adult hippocampal neurogenesis under normal and ischemic conditions.
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Affiliation(s)
- Tsutomu Sasaki
- Division of Stroke Research, Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan.
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209
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Mandairon N, Sacquet J, Jourdan F, Didier A. Long-term fate and distribution of newborn cells in the adult mouse olfactory bulb: Influences of olfactory deprivation. Neuroscience 2006; 141:443-51. [PMID: 16713121 DOI: 10.1016/j.neuroscience.2006.03.066] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 03/15/2006] [Accepted: 03/15/2006] [Indexed: 11/24/2022]
Abstract
The adult subventricular zone produces neuroblasts that migrate to the main olfactory bulb, where they differentiate into interneurons in the glomerular and granular layers. Using bromodeoxyuridine labeling, the survival of newborn cells was assessed in these two layers of the MOB in control mice and in mice unilaterally deprived from sensory input by naris occlusion. In control main olfactory bulbs, bromodeoxyuridine-positive cell density decreased about 70% between 15 and 180 days post-bromodeoxyuridine administration but earlier in the glomerular layer than in the granular layer. At all time points examined, newborn cell density was higher in the deep granular layer than in the superficial granular layer. Occlusion started at the age of 2 months and lasted for 15, 30, 45, 60 or 180 days. The newborn cell survival was similarly reduced in both layers by occlusion, during a critical period 15 and 45 days post-occlusion. Interestingly, olfactory deprivation decreased bromodeoxyuridine-positive cell density in the deep granular layer only, indicating a greater dependence of cell fate on sensory input in this sub-layer. Neuronal differentiation was assessed in the granular layer and glomerular layer by multiple double-labeling 45 days post-bromodeoxyuridine-injections, the time point at which the proportion of bromodeoxyuridine-positive cells expressing a neuronal marker reached approximately 85% in the granular layer and approximately 50% in the glomerular layer. Naris occlusion did not significantly affect these proportions. Taken together, our results reveal that the survival of newborn cells has a different time course in the glomerular layer and in the granular layer, but is similarly decreased in each layer by olfactory deprivation. In addition, our data suggest a functional heterogeneity of neurogenesis within the granular layer.
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Affiliation(s)
- N Mandairon
- Laboratoire de Neurosciences et Systèmes Sensoriels, CNRS UMR 5020, Université Claude Bernard Lyon 1, 50 Avenue Tony Garnier, 6936, Lyon Cedex 07, France.
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210
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Magavi SSP, Mitchell BD, Szentirmai O, Carter BS, Macklis JD. Adult-born and preexisting olfactory granule neurons undergo distinct experience-dependent modifications of their olfactory responses in vivo. J Neurosci 2005; 25:10729-39. [PMID: 16291946 PMCID: PMC6725839 DOI: 10.1523/jneurosci.2250-05.2005] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 09/28/2005] [Accepted: 09/28/2005] [Indexed: 11/21/2022] Open
Abstract
Neurogenesis continues throughout adulthood in the mammalian olfactory bulb and hippocampal dentate gyrus, suggesting the hypothesis that recently generated, adult-born neurons contribute to neural plasticity and learning. To explore this hypothesis, we examined whether olfactory experience modifies the responses of adult-born neurons to odorants, using immediate early genes (IEGs) to assay the response of olfactory granule neurons. We find that, shortly after they differentiate and synaptically integrate, the population of adult-born olfactory granule neurons has a greater population IEG response to novel odors than mature, preexisting neurons. Familiarizing mice with test odors increases the response of the recently incorporated adult-born neuron population to the test odors, and this increased responsiveness is long lasting, demonstrating that the response of the adult-born neuron population is altered by experience. In contrast, familiarizing mice with test odors decreases the IEG response of developmentally generated neurons, suggesting that recently generated adult-born neurons play a distinct role in olfactory processing. The increased IEG response is stimulus specific; familiarizing mice with a set of different, "distractor" odors does not increase the adult-born neuron population response to the test odors. Odor familiarization does not influence the survival of adult-born neurons, indicating that the changes in the population response of adult-born neurons are not attributable to increased survival of odor-stimulated neurons. These results demonstrate that recently generated adult-born olfactory granule neurons and older, preexisting granule neurons undergo contrasting experience-dependent modifications in vivo and support the hypothesis that adult-born neurons are involved in olfactory learning.
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Affiliation(s)
- Sanjay S P Magavi
- Massachusetts General Hospital-Harvard Medical School Center for Nervous System Repair, Department of Neurosurgery, Boston, Massachusetts 02114, USA
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