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Grégoire CA, Bonenfant D, Le Nguyen A, Aumont A, Fernandes KJL. Untangling the influences of voluntary running, environmental complexity, social housing and stress on adult hippocampal neurogenesis. PLoS One 2014; 9:e86237. [PMID: 24465980 PMCID: PMC3900491 DOI: 10.1371/journal.pone.0086237] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 12/10/2013] [Indexed: 01/08/2023] Open
Abstract
Environmental enrichment (EE) exerts powerful effects on brain physiology, and is widely used as an experimental and therapeutic tool. Typical EE paradigms are multifactorial, incorporating elements of physical exercise, environmental complexity, social interactions and stress, however the specific contributions of these variables have not been separable using conventional housing paradigms. Here, we evaluated the impacts of these individual variables on adult hippocampal neurogenesis by using a novel "Alternating EE" paradigm. For 4 weeks, adult male CD1 mice were alternated daily between two enriched environments; by comparing groups that differed in one of their two environments, the individual and combinatorial effects of EE variables could be resolved. The Alternating EE paradigm revealed that (1) voluntary running for 3 days/week was sufficient to increase both mitotic and post-mitotic stages of hippocampal neurogenesis, confirming the central importance of exercise; (2) a complex environment (comprised of both social interactions and rotated inanimate objects) had no effect on neurogenesis itself, but enhanced depolarization-induced c-Fos expression (attributable to social interactions) and buffered stress-induced plasma corticosterone levels (attributable to inanimate objects); and (3) neither social isolation, group housing, nor chronically increased levels of plasma corticosterone had a prolonged impact on neurogenesis. Mouse strain, handling and type of running apparatus were tested and excluded as potential confounding factors. These findings provide valuable insights into the relative effects of key EE variables on adult neurogenesis, and this "Alternating EE" paradigm represents a useful tool for exploring the contributions of individual EE variables to mechanisms of neural plasticity.
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Affiliation(s)
- Catherine-Alexandra Grégoire
- Department of Pathology and Cell Biology, Groupe de recherche sur le système nerveux central (GRSNC), and Center of Excellence in Neuroscience of the Université de Montréal (CENUM), Université de Montréal, Montréal, Canada
| | - David Bonenfant
- Department of Pathology and Cell Biology, Groupe de recherche sur le système nerveux central (GRSNC), and Center of Excellence in Neuroscience of the Université de Montréal (CENUM), Université de Montréal, Montréal, Canada
| | - Adalie Le Nguyen
- Department of Pathology and Cell Biology, Groupe de recherche sur le système nerveux central (GRSNC), and Center of Excellence in Neuroscience of the Université de Montréal (CENUM), Université de Montréal, Montréal, Canada
| | - Anne Aumont
- Department of Pathology and Cell Biology, Groupe de recherche sur le système nerveux central (GRSNC), and Center of Excellence in Neuroscience of the Université de Montréal (CENUM), Université de Montréal, Montréal, Canada
| | - Karl J. L. Fernandes
- Department of Pathology and Cell Biology, Groupe de recherche sur le système nerveux central (GRSNC), and Center of Excellence in Neuroscience of the Université de Montréal (CENUM), Université de Montréal, Montréal, Canada
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102
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Tapia-González S, Muñoz MD, Cuartero MI, Sánchez-Capelo A. Smad3 is required for the survival of proliferative intermediate progenitor cells in the dentate gyrus of adult mice. Cell Commun Signal 2013; 11:93. [PMID: 24330661 PMCID: PMC4029396 DOI: 10.1186/1478-811x-11-93] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 12/06/2013] [Indexed: 12/16/2022] Open
Abstract
Background New neurons are continuously being generated in the adult hippocampus, a phenomenon that is regulated by external stimuli, such as learning, memory, exercise, environment or stress. However, the molecular mechanisms underlying neuron production and how they are integrated into existing circuits under such physiological conditions remain unclear. Indeed, the intracellular modulators that transduce the extracellular signals are not yet fully understood. Results We show that Smad3, an intracellular molecule involved in the transforming growth factor (TGF)-β signaling cascade, is strongly expressed by granule cells in the dentate gyrus (DG) of adult mice, although the loss of Smad3 in null mutant mice does not affect their survival. Smad3 is also expressed by adult progenitor cells in the subgranular zone (SGZ) and more specifically, it is first expressed by Type 2 cells (intermediate progenitor cells). Its expression persists through the distinct cell stages towards that of the mature neuron. Interestingly, proliferative intermediate progenitor cells die in Smad3 deficiency, which is associated with a large decrease in the production of newborn neurons in Smad3 deficient mice. Smad3 signaling appears to influence adult neurogenesis fulfilling distinct roles in the rostral and mid-caudal regions of the DG. In rostral areas, Smad3 deficiency increases proliferation and promotes the cell cycle exit of undifferentiated progenitor cells. By contrast, Smad3 deficiency impairs the survival of newborn neurons in the mid-caudal region of the DG at early proliferative stages, activating apoptosis of intermediate progenitor cells. Furthermore, long-term potentiation (LTP) after high frequency stimulation (HFS) to the medial perforant path (MPP) was abolished in the DG of Smad3-deficient mice. Conclusions These data show that endogenous Smad3 signaling is central to neurogenesis and LTP induction in the adult DG, these being two forms of hippocampal brain plasticity related to learning and memory that decline with aging and as a result of neurological disorders.
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Affiliation(s)
| | | | | | - Amelia Sánchez-Capelo
- CIBERNED - Ser, Neurobiología-Investigación, Hospital Universitario Ramón y Cajal-IRYCIS, Ctra, Colmenar Viejo Km 9, 28034 Madrid, Spain.
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103
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Barr A, Wu C, Wong C, Hercher C, Töpfer E, Boyda H, Procyshyn R, Honer W, Beasley C. Effects of chronic exercise and treatment with the antipsychotic drug olanzapine on hippocampal volume in adult female rats. Neuroscience 2013; 255:147-57. [DOI: 10.1016/j.neuroscience.2013.10.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 10/03/2013] [Accepted: 10/07/2013] [Indexed: 02/04/2023]
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104
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Nishijima T, Kawakami M, Kita I. Long-term exercise is a potent trigger for ΔFosB induction in the hippocampus along the dorso-ventral axis. PLoS One 2013; 8:e81245. [PMID: 24282574 PMCID: PMC3840114 DOI: 10.1371/journal.pone.0081245] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 10/21/2013] [Indexed: 01/31/2023] Open
Abstract
Physical exercise improves multiple aspects of hippocampal function. In line with the notion that neuronal activity is key to promoting neuronal functions, previous literature has consistently demonstrated that acute bouts of exercise evoke neuronal activation in the hippocampus. Repeated activating stimuli lead to an accumulation of the transcription factor ΔFosB, which mediates long-term neural plasticity. In this study, we tested the hypothesis that long-term voluntary wheel running induces ΔFosB expression in the hippocampus, and examined any potential region-specific effects within the hippocampal subfields along the dorso–ventral axis. Male C57BL/6 mice were housed with or without a running wheel for 4 weeks. Long-term wheel running significantly increased FosB/ΔFosB immunoreactivity in all hippocampal regions measured (i.e., in the DG, CA1, and CA3 subfields of both the dorsal and ventral hippocampus). Results confirmed that wheel running induced region-specific expression of FosB/ΔFosB immunoreactivity in the cortex, suggesting that the uniform increase in FosB/ΔFosB within the hippocampus is not a non-specific consequence of running. Western blot data indicated that the increased hippocampal FosB/ΔFosB immunoreactivity was primarily due to increased ΔFosB. These results suggest that long-term physical exercise is a potent trigger for ΔFosB induction throughout the entire hippocampus, which would explain why exercise can improve both dorsal and ventral hippocampus-dependent functions. Interestingly, we found that FosB/ΔFosB expression in the DG was positively correlated with the number of doublecortin-immunoreactive (i.e., immature) neurons. Although the mechanisms by which ΔFosB mediates exercise-induced neurogenesis are still uncertain, these data imply that exercise-induced neurogenesis is at least activity dependent. Taken together, our current results suggest that ΔFosB is a new molecular target involved in regulating exercise-induced hippocampal plasticity.
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Affiliation(s)
- Takeshi Nishijima
- Laboratory of Behavioral Physiology, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan
- * E-mail:
| | - Masashi Kawakami
- Laboratory of Behavioral Physiology, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Ichiro Kita
- Laboratory of Behavioral Physiology, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan
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105
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Neurogenesis along the septo-temporal axis of the hippocampus: Are depression and the action of antidepressants region-specific? Neuroscience 2013; 252:234-52. [DOI: 10.1016/j.neuroscience.2013.08.017] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 07/01/2013] [Accepted: 08/12/2013] [Indexed: 01/25/2023]
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106
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Gheidi A, Azzopardi E, Adams AA, Marrone DF. Experience-dependent persistent expression of zif268 during rest is preserved in the aged dentate gyrus. BMC Neurosci 2013; 14:100. [PMID: 24028087 PMCID: PMC3848627 DOI: 10.1186/1471-2202-14-100] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 09/10/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Aging is typically accompanied by memory decline and changes in hippocampal function. Among these changes is a decline in the activity of the dentate gyrus (DG) during behavior. Lasting memory, however, is thought to also require recapitulation of recent memory traces during subsequent rest - a phenomenon, termed memory trace reactivation, which is compromised in hippocampal CA1 with progressive age. This process has yet to be assessed in the aged DG, despite its prominent role in age-related memory impairment. Using zif268 transcription to measure granule cell recruitment, DG activity in adult and aged animals was assessed both during spatial exploration and as animals remained at rest in the home cage in order to detect potential memory-related replay. RESULTS Consistent with the observation of memory trace reactivation in DG, the probability that an individual granule cell transcribes zif268 during rest in the animal's home cage is increased by recent experience in a novel environment. Surprisingly, a comparable increase was observed in the probability of granule cells in the aged DG expressing zif268 during rest. Moreover, no significant age-related difference was observed in the number of granule cells expressing zif268 during rest. Thus, the number and pattern of granule cell expression of zif268 during rest is preserved in aged animals, despite a significant decline in exploration-related zif268 expression. CONCLUSIONS These data lead to the hypothesis that the input the aged DG receives from backprojections from CA3 (the region widely hypothesized to mediate reactivation) remains functionally intact despite loss of innervation from the perforant path.
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Affiliation(s)
- Ali Gheidi
- Department of Psychology, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON N2L 3C5, Canada
| | - Erin Azzopardi
- Department of Psychology, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON N2L 3C5, Canada
| | - Allison A Adams
- Department of Psychology, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON N2L 3C5, Canada
| | - Diano F Marrone
- Department of Psychology, Wilfrid Laurier University, 75 University Ave W, Waterloo, ON N2L 3C5, Canada
- McKnight Brain Institute, University of Arizona, Tucson, AZ 85724, USA
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107
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Chow C, Epp JR, Lieblich SE, Barha CK, Galea LAM. Sex differences in neurogenesis and activation of new neurons in response to spatial learning and memory. Psychoneuroendocrinology 2013; 38:1236-50. [PMID: 23219473 DOI: 10.1016/j.psyneuen.2012.11.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Revised: 10/30/2012] [Accepted: 11/07/2012] [Indexed: 11/29/2022]
Abstract
Adult hippocampal neurogenesis is often associated with hippocampus-dependent learning and memory. Throughout a new neuron's development, it is differentially sensitive to factors that can influence its survival and functionality. Previous research shows that spatial training that occurred 6-10 days after an injection of the DNA synthesis marker, bromodeoxyuridine (BrdU), increased cell survival in male rats. Because sex differences in spatial cognition and hippocampal neurogenesis have been reported, it is unclear whether spatial training would influence hippocampal neurogenesis in the same way in males and females. Therefore, this study examined sex differences in hippocampal neurogenesis following training in a spatial task. Male and female rats were trained in the spatial or cued version of the Morris water maze 6-10 days after one injection of BrdU (200mg/kg). Twenty days following BrdU injection, all animals were given a probe trial and perfused. Males performed better in the spatial, but not cue, task than females. Spatial training increased BrdU-labeled cells relative to cue training only in males, but both males and females showed greater activation of new cells (BrdU co-labeled with immediate early gene product zif268) after spatial training compared to cue training. Furthermore, performance during spatial training was positively correlated with cell activation in females but not males. This study shows that while spatial training differentially regulates hippocampal neurogenesis in males and females, the activity of new neurons in response to spatial memory retrieval is similar. These findings highlight the importance of sex on neural plasticity and cognition.
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Affiliation(s)
- Carmen Chow
- Program in Neuroscience, Department of Psychology, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada
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108
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Physical exercise prevents stress-induced activation of granule neurons and enhances local inhibitory mechanisms in the dentate gyrus. J Neurosci 2013; 33:7770-7. [PMID: 23637169 DOI: 10.1523/jneurosci.5352-12.2013] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Physical exercise is known to reduce anxiety. The ventral hippocampus has been linked to anxiety regulation but the effects of running on this subregion of the hippocampus have been incompletely explored. Here, we investigated the effects of cold water stress on the hippocampus of sedentary and runner mice and found that while stress increases expression of the protein products of the immediate early genes c-fos and arc in new and mature granule neurons in sedentary mice, it has no such effect in runners. We further showed that running enhances local inhibitory mechanisms in the hippocampus, including increases in stress-induced activation of hippocampal interneurons, expression of vesicular GABA transporter (vGAT), and extracellular GABA release during cold water swim stress. Finally, blocking GABAA receptors in the ventral hippocampus, but not the dorsal hippocampus, with the antagonist bicuculline, reverses the anxiolytic effect of running. Together, these results suggest that running improves anxiety regulation by engaging local inhibitory mechanisms in the ventral hippocampus.
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109
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Wosiski-Kuhn M, Stranahan AM. From pattern separation to mood regulation: multiple roles for developmental signals in the adult dentate gyrus. Front Cell Neurosci 2013; 7:96. [PMID: 23805072 PMCID: PMC3693068 DOI: 10.3389/fncel.2013.00096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 06/03/2013] [Indexed: 01/01/2023] Open
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110
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Tanti A, Westphal WP, Girault V, Brizard B, Devers S, Leguisquet AM, Surget A, Belzung C. Region-dependent and stage-specific effects of stress, environmental enrichment, and antidepressant treatment on hippocampal neurogenesis. Hippocampus 2013; 23:797-811. [DOI: 10.1002/hipo.22134] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/05/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Arnaud Tanti
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
| | | | - Virginie Girault
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
| | - Bruno Brizard
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
| | - Severine Devers
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
| | | | - Alexandre Surget
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
| | - Catherine Belzung
- INSERM UMR930; Tours France
- Université François Rabelais; Tours France
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111
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Veyrac A, Gros A, Bruel-Jungerman E, Rochefort C, Kleine Borgmann FB, Jessberger S, Laroche S. Zif268/egr1 gene controls the selection, maturation and functional integration of adult hippocampal newborn neurons by learning. Proc Natl Acad Sci U S A 2013; 110:7062-7. [PMID: 23569253 PMCID: PMC3637756 DOI: 10.1073/pnas.1220558110] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
New neurons are continuously added to the dentate gyrus of the adult mammalian brain. During the critical period of a few weeks after birth when newborn neurons progressively mature, a restricted fraction is competitively selected to survive in an experience-dependent manner, a condition for their contribution to memory processes. The mechanisms that control critical stages of experience-dependent functional incorporation of adult newborn neurons remain largely unknown. Here, we identify a unique transcriptional regulator of the functional integration of newborn neurons, the inducible immediate early gene zif268/egr1. We show that newborn neurons in zif268-KO mice undergo accelerated death during the critical period of 2-3 wk around their birth and exhibit deficient neurochemical and morphological maturation, including reduced GluR1 expression, increased NKCC1/KCC2b chloride cotransporter ratio, altered dendritic development, and marked spine growth defect. Investigating responsiveness of newborn neurons to activity-dependent expression of zif268 in learning, we demonstrate that in the absence of zif268, training in a spatial learning task during this critical period fails to recruit newborn neurons and promote their survival, leading to impaired long-term memory. This study reveals a previously unknown mechanism for the control of the selection, functional maturation, and experience-dependent recruitment of dentate gyrus newborn neurons that depends on the inducible immediate early gene zif268, processes that are critical for their contribution to hippocampal-dependent long-term memory.
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Affiliation(s)
- Alexandra Veyrac
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195, F-91405 Orsay, France
- Université Paris-Sud, Centre de Neurosciences Paris-Sud, F-91405 Orsay, France; and
| | - Alexandra Gros
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195, F-91405 Orsay, France
- Université Paris-Sud, Centre de Neurosciences Paris-Sud, F-91405 Orsay, France; and
| | - Elodie Bruel-Jungerman
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195, F-91405 Orsay, France
- Université Paris-Sud, Centre de Neurosciences Paris-Sud, F-91405 Orsay, France; and
| | - Christelle Rochefort
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195, F-91405 Orsay, France
- Université Paris-Sud, Centre de Neurosciences Paris-Sud, F-91405 Orsay, France; and
| | | | | | - Serge Laroche
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195, F-91405 Orsay, France
- Université Paris-Sud, Centre de Neurosciences Paris-Sud, F-91405 Orsay, France; and
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112
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Epp JR, Chow C, Galea LAM. Hippocampus-dependent learning influences hippocampal neurogenesis. Front Neurosci 2013; 7:57. [PMID: 23596385 PMCID: PMC3627134 DOI: 10.3389/fnins.2013.00057] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Accepted: 03/28/2013] [Indexed: 12/26/2022] Open
Abstract
The structure of the mammalian hippocampus continues to be modified throughout life by continuous addition of neurons in the dentate gyrus. Although the existence of adult neurogenesis is now widely accepted the function that adult generated granule cells play is a topic of intense debate. Many studies have argued that adult generated neurons, due to unique physiological characteristics, play a unique role in hippocampus-dependent learning and memory. However, it is not currently clear whether this is the case or what specific capability adult generated neurons may confer that developmentally generated neurons do not. These questions have been addressed in numerous ways, from examining the effects of increasing or decreasing neurogenesis to computational modeling. One particular area of research has examined the effects of hippocampus dependent learning on proliferation, survival, integration and activation of immature neurons in response to memory retrieval. Within this subfield there remains a range of data showing that hippocampus dependent learning may increase, decrease or alternatively may not alter these components of neurogenesis in the hippocampus. Determining how and when hippocampus-dependent learning alters adult neurogenesis will help to further clarify the role of adult generated neurons. There are many variables (such as age of immature neurons, species, strain, sex, stress, task difficulty, and type of learning) as well as numerous methodological differences (such as marker type, quantification techniques, apparatus size etc.) that could all be crucial for a clear understanding of the interaction between learning and neurogenesis. Here, we review these findings and discuss the different conditions under which hippocampus-dependent learning impacts adult neurogenesis in the dentate gyrus.
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Affiliation(s)
- Jonathan R. Epp
- *Correspondence: Jonathan R. Epp, Neurosciences and Mental Health, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada. e-mail: ;
| | | | - Liisa A. M. Galea
- Department of Psychology, Program in Neuroscience, Brain Research Centre, University of British ColumbiaVancouver, BC, Canada
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113
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Hillerer KM, Neumann ID, Couillard-Despres S, Aigner L, Slattery DA. Sex-dependent regulation of hippocampal neurogenesis under basal and chronic stress conditions in rats. Hippocampus 2013; 23:476-87. [DOI: 10.1002/hipo.22107] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2013] [Indexed: 12/16/2022]
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114
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Pubertally born neurons and glia are functionally integrated into limbic and hypothalamic circuits of the male Syrian hamster. Proc Natl Acad Sci U S A 2013; 110:4792-7. [PMID: 23460698 DOI: 10.1073/pnas.1219443110] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
During puberty, the brain goes through extensive remodeling, involving the addition of new neurons and glia to brain regions beyond the canonical neurogenic regions (i.e., dentate gyrus and olfactory bulb), including limbic and hypothalamic cell groups associated with sex-typical behavior. Whether these pubertally born cells become functionally integrated into neural circuits remains unknown. To address this question, we gave male Syrian hamsters daily injections of the cell birthdate marker bromodeoxyuridine throughout puberty (postnatal day 28-49). Half of the animals were housed in enriched environments with access to a running wheel to determine whether enrichment increased the survival of pubertally born cells compared with the control environment. At 4 wk after the last BrdU injection, animals were allowed to interact with a receptive female and were then killed 1 h later. Triple-label immunofluorescence for BrdU, the mature neuron marker neuronal nuclear antigen, and the astrocytic marker glial fibrillary acidic protein revealed that a proportion of pubertally born cells in the medial preoptic area, arcuate nucleus, and medial amygdala differentiate into either mature neurons or astrocytes. Double-label immunofluorescence for BrdU and the protein Fos revealed that a subset of pubertally born cells in these regions is activated during sociosexual behavior, indicative of their functional incorporation into neural circuits. Enrichment affected the survival and activation of pubertally born cells in a brain region-specific manner. These results demonstrate that pubertally born cells located outside of the traditional neurogenic regions differentiate into neurons and glia and become functionally incorporated into neural circuits that subserve sex-typical behaviors.
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115
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Schoenfeld TJ, Gould E. Differential effects of stress and glucocorticoids on adult neurogenesis. Curr Top Behav Neurosci 2013; 15:139-164. [PMID: 23670817 DOI: 10.1007/7854_2012_233] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Stress is known to inhibit neuronal growth in the hippocampus. In addition to reducing the size and complexity of the dendritic tree, stress and elevated glucocorticoid levels are known to inhibit adult neurogenesis. Despite the negative effects of stress hormones on progenitor cell proliferation in the hippocampus, some experiences which produce robust increases in glucocorticoid levels actually promote neuronal growth. These experiences, including running, mating, enriched environment living, and intracranial self-stimulation, all share in common a strong hedonic component. Taken together, the findings suggest that rewarding experiences buffer progenitor cells in the dentate gyrus from the negative effects of elevated stress hormones. This chapter considers the evidence that stress and glucocorticoids inhibit neuronal growth along with the paradoxical findings of enhanced neuronal growth under rewarding conditions with a view toward understanding the underlying biological mechanisms.
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Affiliation(s)
- Timothy J Schoenfeld
- Department of Psychology, Neuroscience Institute, Princeton University, Princeton, NJ, 08545, USA
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116
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Hawley DF, Morch K, Christie BR, Leasure JL. Differential response of hippocampal subregions to stress and learning. PLoS One 2012; 7:e53126. [PMID: 23285257 PMCID: PMC3532167 DOI: 10.1371/journal.pone.0053126] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 11/27/2012] [Indexed: 11/19/2022] Open
Abstract
The hippocampus has two functionally distinct subregions-the dorsal portion, primarily associated with spatial navigation, and the ventral portion, primarily associated with anxiety. In a prior study of chronic unpredictable stress (CUS) in rodents, we found that it selectively enhanced cellular plasticity in the dorsal hippocampal subregion while negatively impacting it in the ventral. In the present study, we determined whether this adaptive plasticity in the dorsal subregion would confer CUS rats an advantage in a spatial task-the radial arm water maze (RAWM). RAWM exposure is both stressful and requires spatial navigation, and therefore places demands simultaneously upon both hippocampal subregions. Therefore, we used Western blotting to investigate differential expression of plasticity-associated proteins (brain derived neurotrophic factor [BDNF], proBDNF and postsynaptic density-95 [PSD-95]) in the dorsal and ventral subregions following RAWM exposure. Lastly, we used unbiased stereology to compare the effects of CUS on proliferation, survival and neuronal differentiation of cells in the dorsal and ventral hippocampal subregions. We found that CUS and exposure to the RAWM both increased corticosterone, indicating that both are stressful; nevertheless, CUS animals had significantly better long-term spatial memory. We also observed a subregion-specific pattern of protein expression following RAWM, with proBDNF increased in the dorsal and decreased in the ventral subregion, while PSD-95 was selectively upregulated in the ventral. Finally, consistent with our previous study, we found that CUS most negatively affected neurogenesis in the ventral (compared to the dorsal) subregion. Taken together, our data support a dual role for the hippocampus in stressful experiences, with the more resilient dorsal portion undergoing adaptive plasticity (perhaps to facilitate escape from or neutralization of the stressor), and the ventral portion involved in affective responses.
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Affiliation(s)
- Darby F. Hawley
- Department of Psychology, University of Houston, Houston, Texas, United States of America
| | - Kristin Morch
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - Brian R. Christie
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
- Island Medical Program, University of British Columbia, Victoria, British Columbia, Canada
| | - J. Leigh Leasure
- Department of Psychology, University of Houston, Houston, Texas, United States of America
- Department of Biology & Biochemistry, University of Houston, Houston, Texas, United States of America
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117
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Tomi M, Zhao Y, Thamotharan S, Shin BC, Devaskar SU. Early life nutrient restriction impairs blood-brain metabolic profile and neurobehavior predisposing to Alzheimer's disease with aging. Brain Res 2012; 1495:61-75. [PMID: 23228723 DOI: 10.1016/j.brainres.2012.11.050] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 11/05/2012] [Accepted: 11/29/2012] [Indexed: 12/26/2022]
Abstract
Prenatal nutrient restriction (NR) culminating in intra-uterine growth restriction (IUGR) with postnatal catch up growth leads to diabesity. In contrast, postnatal NR with growth restriction (PNGR) superimposed on IUGR (IPGR) protects young and aging adults from this phenotype. We hypothesized that PNGR/IPGR will compromise the blood-brain metabolic profile impairing neurobehavior and predisposing to Alzheimer's disease (AD). NR (50%) in late gestation followed by cross-fostering of rat pups to either ad lib fed (CON) or NR (50%) lactating mothers generated CON, IUGR, PNGR and IPGR male (M) and female (F) offspring that were examined through the life span. In PNGR/IPGR plasma/CSF glucose and lactate decreased while ketones increased in (M) and (F) (PN21, PN50). In addition increased brain glucose transporters, Glut1 & Glut3, greater brain derived neurotrophic factor (BDNF), reduced Glut4, with unchanged serotonin transporter concentrations were noted in (F) (PN50-60). While (F) displayed more hyperactivity, both (F) and (M) exhibited anxiety although socially and cognitively unimpaired (PN25-28&50). Aging (15-17 m) (F) not (M), expressed low plasma insulin, reduced brain IRS-2, pAkt, and pGSK-3β(Ser9), unchanged pPDK1, pTau or lipoprotein receptor related protein 1 (LRP1), higher glial fibrillary acidic protein (GFAP) and spinophilin but a 10-fold increased amyloid-β42. We conclude that therapeutically superimposing PNGR on IUGR (IPGR) should be carefully weighed in light of unintended consequences related to perturbed neurobehavior and potential predilection for AD.
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Affiliation(s)
- Masatoshi Tomi
- Department of Pediatrics, Division of Neonatology and Developmental Biology, Neonatal Research Center, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752, USA
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118
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Snyder JS, Ferrante SC, Cameron HA. Late maturation of adult-born neurons in the temporal dentate gyrus. PLoS One 2012; 7:e48757. [PMID: 23144957 PMCID: PMC3492442 DOI: 10.1371/journal.pone.0048757] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 10/02/2012] [Indexed: 12/28/2022] Open
Abstract
Hippocampal function varies along its septotemporal axis, with the septal (dorsal) pole more frequently involved in spatial learning and memory and the temporal (ventral) pole playing a greater role in emotional behaviors. One feature that varies across these subregions is adult neurogenesis. New neurons are more numerous in the septal hippocampus but are more active in the temporal hippocampus during water maze training. However, many other aspects of adult neurogenesis remain unexplored in the context of septal versus temporal subregions. In addition, the dentate gyrus contains another functionally important anatomical division along the transverse axis, with the suprapyramidal blade showing greater experience-related activity than the infrapyramidal blade. Here we ask whether new neurons differ in their rates of survival and maturation along the septotemporal and transverse axes. We found that neurogenesis is initially higher in the infrapyramidal than suprapyramidal blade, but these cells are less likely to survive, resulting in similar densities of neurons in the two blades by four weeks. Across the septotemporal axis, neurogenesis was higher in septal than temporal pole, while the survival rate of new neurons did not differ. Maturation was assessed by immunostaining for the neuronal marker, NeuN, which increases in expression level with maturation, and for the immediate-early gene, Arc, which suggests a neuron is capable of undergoing activity-dependent synaptic plasticity. Maturation occurred approximately 1-2 weeks earlier in the septal pole than in the temporal pole. This suggests that septal neurons may contribute to function sooner; however, the prolonged maturation of new temporal neurons may endow them with a longer window of plasticity during which their functions could be distinct from those of the mature granule cell population. These data point to subregional differences in new neuron maturation and suggest that changes in neurogenesis could alter different hippocampus-dependent behaviors with different time courses.
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Affiliation(s)
- Jason S Snyder
- Unit on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States of America.
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119
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Matsumata M, Sakayori N, Maekawa M, Owada Y, Yoshikawa T, Osumi N. The effects of Fabp7 and Fabp5 on postnatal hippocampal neurogenesis in the mouse. Stem Cells 2012; 30:1532-43. [PMID: 22581784 DOI: 10.1002/stem.1124] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
New neurons are continually produced after birth from neural stem/progenitor cells (NSCs/NPCs) in the hippocampal dentate gyrus (DG). Recent studies have reported that fatty acid binding protein 7 (Fabp7/brain lipid binding protein (BLBP)) is required for the maintenance of embryonic NSCs/NPCs and have identified an association between the Fabp7 gene and behavioral paradigms that correlate with hippocampal functions. However, the specific roles of Fabps in postnatal neurogenesis remain unknown. Herein, we demonstrate the effects of Fabp7, and another Fabp, Fabp5, on postnatal neurogenesis. Fabp7 and Fabp5 were detected in the subgranular zone (SGZ) of the DG, and Fabp7+ cells were less differentiated than Fabp5+ cells. We analyzed the differentiation state of NSCs/NPCs in the SGZ of 4-week-old (4w) Fabp7 knockout (7KO), Fabp5 KO (5KO), and Fabp7/Fabp5 double KO (7/5KO) mice and found that the number of NSCs/NPCs was dramatically reduced compared with wild-type mice. Although the uptake of BrdU 1 day after injection was decreased in all KO mice, the survival of BrdU+ cells 1 month after injection was increased in the 7/5KO mice compared to other three genotypes. We also observed an enhancement of neuronal differentiation in all Fabp KO mice. In addition, the proliferation and survival of NSCs/NPCs differed along the anterior-posterior axis (A-P axis). A greater number of newborn cells in the posterior region became extinct, but this tendency was not apparent in the Fabps KO mice. These data suggest that Fabp7 and Fabp5 have differential roles for proliferation and survival of the NSCs/NPCs during postnatal DG neurogenesis.
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Affiliation(s)
- Miho Matsumata
- Division of Developmental Neuroscience, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University School of Medicine, Sendai, Japan
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120
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Differential environmental regulation of neurogenesis along the septo-temporal axis of the hippocampus. Neuropharmacology 2012; 63:374-84. [DOI: 10.1016/j.neuropharm.2012.04.022] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 04/16/2012] [Accepted: 04/19/2012] [Indexed: 01/06/2023]
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121
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Goodman T, Crandall JE, Nanescu SE, Quadro L, Shearer K, Ross A, McCaffery P. Patterning of retinoic acid signaling and cell proliferation in the hippocampus. Hippocampus 2012; 22:2171-83. [PMID: 22689466 PMCID: PMC3505796 DOI: 10.1002/hipo.22037] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2012] [Indexed: 12/23/2022]
Abstract
The nuclear receptor ligand retinoic acid (RA) has been identified as an endogenous regulatory factor in the hippocampus, acting on pyramidal neurons and granule neuron progenitors, but almost nothing is known about the distribution of RA itself in the hippocampus. This study describes the source of RA for the rodent hippocampus in the meninges via the key RA synthetic enzyme retinaldehyde dehydrogenase 2 (RALDH2). Diffusion of RA from the meninges potentially creates a gradient of RA across the infrapyramidal and suprapyramidal blades of the dentate gyrus, enhanced by the expression of the RA catabolic enzyme Cyp26B1 between the blades, and an infrapyramidal and suprapyramidal blade difference is evident in RA-regulated transcription. This asymmetry may contribute to some of the physiological and molecular differences between the blades, including a disparity in the rates of cell proliferation in the subgranular zone of the two blades through RA inhibition of cell proliferation. Such differences can be altered by either the application of excess RA, its effect dependent on the relative position along the septotemporal axis, or change in RA signaling through mutation of retinol binding protein, while the capacity of RA to inhibit proliferation of cells in the dentate gyrus is demonstrated using in vitro slice culture. Use of synthetic and catabolic enzymes in the hippocampus to create differing zones of RA concentration parallels the mechanisms used in the developing brain to generate patterns of RA-regulated transcription. © 2012 Wiley Periodicals, Inc.
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Affiliation(s)
- Timothy Goodman
- Institute of Medical Sciences, University of Aberdeen, Aberdeenshire, United Kingdom
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122
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Jhaveri DJ, Taylor CJ, Bartlett PF. Activation of different neural precursor populations in the adult hippocampus: Does this lead to new neurons with discrete functions? Dev Neurobiol 2012; 72:1044-58. [DOI: 10.1002/dneu.22027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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123
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Garrett L, Lie DC, Hrabé de Angelis M, Wurst W, Hölter SM. Voluntary wheel running in mice increases the rate of neurogenesis without affecting anxiety-related behaviour in single tests. BMC Neurosci 2012; 13:61. [PMID: 22682077 PMCID: PMC3504529 DOI: 10.1186/1471-2202-13-61] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 06/08/2012] [Indexed: 11/21/2022] Open
Abstract
Background The role played by adult neurogenesis in anxiety is not clear. A recent study revealed a surprising positive correlation between increased anxiety and elevated neurogenesis following chronic voluntary wheel running and multiple behavioural testing in mice, suggesting that adult hippocampal neurogenesis is involved in the genesis of anxiety. To exclude the possible confounding effect of multiple testing that may have occurred in the aforementioned study, we assessed (1) the effects of mouse voluntary wheel running (14 vs. 28 days) on anxiety in just one behavioural test; the open field, and (2), using different markers, proliferation, differentiation, survival and maturation of newly born neurons in the dentate gyrus immediately afterwards. Effects of wheel running on anxiety-related behaviour were confirmed in a separate batch of animals tested in another test of anxiety, the light/dark box test. Results Running altered measures of locomotion and exploration, but not anxiety-related behaviour in either test. 14 days running significantly increased proliferation, and differentiation and survival were increased after both running durations. 28 day running mice also exhibited an increased rate of maturation. Furthermore, there was a significant positive correlation between the amount of proliferation, but not maturation, and anxiety measures in the open field of the 28 day running mice. Conclusions Overall, this evidence suggests that without repeated testing, newly born mature neurons may not be involved in the genesis of anxiety per se.
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Affiliation(s)
- Lillian Garrett
- Institute of Developmental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg/Munich, Germany
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124
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Short-term long chain omega3 diet protects from neuroinflammatory processes and memory impairment in aged mice. PLoS One 2012; 7:e36861. [PMID: 22662127 PMCID: PMC3360741 DOI: 10.1371/journal.pone.0036861] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 04/10/2012] [Indexed: 12/20/2022] Open
Abstract
Regular consumption of food enriched in omega3 polyunsaturated fatty acids (ω3 PUFAs) has been shown to reduce risk of cognitive decline in elderly, and possibly development of Alzheimer's disease. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the most likely active components of ω3-rich PUFAs diets in the brain. We therefore hypothesized that exposing mice to a DHA and EPA enriched diet may reduce neuroinflammation and protect against memory impairment in aged mice. For this purpose, mice were exposed to a control diet throughout life and were further submitted to a diet enriched in EPA and DHA during 2 additional months. Cytokine expression together with a thorough analysis of astrocytes morphology assessed by a 3D reconstruction was measured in the hippocampus of young (3-month-old) and aged (22-month-old) mice. In addition, the effects of EPA and DHA on spatial memory and associated Fos activation in the hippocampus were assessed. We showed that a 2-month EPA/DHA treatment increased these long-chain ω3 PUFAs in the brain, prevented cytokines expression and astrocytes morphology changes in the hippocampus and restored spatial memory deficits and Fos-associated activation in the hippocampus of aged mice. Collectively, these data indicated that diet-induced accumulation of EPA and DHA in the brain protects against neuroinflammation and cognitive impairment linked to aging, further reinforcing the idea that increased EPA and DHA intake may provide protection to the brain of aged subjects.
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125
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Jinno S. Topographic differences in adult neurogenesis in the mouse hippocampus: a stereology-based study using endogenous markers. Hippocampus 2012; 21:467-80. [PMID: 20087889 DOI: 10.1002/hipo.20762] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The hippocampus plays a critical role in various cognitive and affective functions. Increasing evidence shows that these functions are topographically distributed along the dorsoventral (septotemporal) and transverse axes of the hippocampus. For instance, dorsal hippocampus is involved in spatial memory and learning whereas ventral hippocampus is related to emotion. Here, we examined the topographic differences (dorsal vs. ventral; suprapyramidal vs. infrapyramidal) in adult neurogenesis in the mouse hippocampus using endogenous markers. The optical disector was applied to estimate the numerical densities (NDs) of labeled cells in the granule cell layer. The NDs of radial glia-like progenitors labeled by brain lipid binding protein were significantly lower in the infrapyramidal blade of the ventral DG than in other subdivisions. The NDs of doublecortin-expressing cells presumed neural progenitors and immature granule cells were significantly higher in the suprapyramidal blade of the dorsal DG than in the other subdivisions. The NDs of calretinin-expressing cells presumed young granule cells at the postmitotic stage were significantly higher in the suprapyramidal blade than in the infrapyramidal blade in the dorsal DG. No significant regional differences were detected in the NDs of dividing cells identified by proliferating cell nuclear antigen. Taken together, these findings suggest that a larger pool of immature granule cells in dorsal hippocampus might be responsible for spatial learning and memory, whereas a smaller pool of radial glia-like progenitors in ventral hippocampus might be associated with the susceptibility to affective disorders. Cell number estimation using a 300-μm-thick hypothetical slice indicates that regional differences in immature cells might contribute to the formation of topographic gradients in mature granule cells in the adult hippocampus. Our data also emphasizes the importance of considering such differences when evaluating changes in adult neurogenesis in pathological conditions and following experimental procedures.
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Affiliation(s)
- Shozo Jinno
- Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
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126
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Marín-Burgin A, Schinder AF. Requirement of adult-born neurons for hippocampus-dependent learning. Behav Brain Res 2012; 227:391-9. [DOI: 10.1016/j.bbr.2011.07.001] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 06/29/2011] [Accepted: 07/01/2011] [Indexed: 02/07/2023]
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127
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Satvat E, Gheidi A, Voll S, Odintsova IV, Marrone DF. Location is everything: neurons born during fluoxetine treatment accumulate in regions that do not support spatial learning. Neuropharmacology 2011; 62:1627-33. [PMID: 22182782 DOI: 10.1016/j.neuropharm.2011.11.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Revised: 11/28/2011] [Accepted: 11/30/2011] [Indexed: 12/30/2022]
Abstract
It is well known that antidepressants both improve mood and increase the rate at which the dentate gyrus (DG) generates new neurons. In addition to the implications of neurogenesis for mood regulation, the production and survival of granule cells has also been implicated in learning and memory. Despite this evidence, the results of studies on the effect of antidepressants on memory have been mixed. A critical piece of data that may be missing from previous studies, however, is insight into (a) the location that newborn neurons migrate to following fluoxetine administration and (b) their ability to express normal patterns of activity-related genes. Here we demonstrate a finding that may resolve the discrepancy in the effects fluoxetine-induced neurogenesis on mood and memory: after 5 weeks delay, the net additional neurons generated in animals given the antidepressant fluoxetine during treatment are functionally normal, but preferentially accumulate (due to changes in migration and/or survival) in an area of the DG that is not recruited by spatial memory tasks.
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Affiliation(s)
- Elham Satvat
- Dept. of Psychology, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
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128
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Hanson ND, Owens MJ, Nemeroff CB. Depression, antidepressants, and neurogenesis: a critical reappraisal. Neuropsychopharmacology 2011; 36:2589-602. [PMID: 21937982 PMCID: PMC3230505 DOI: 10.1038/npp.2011.220] [Citation(s) in RCA: 211] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The neurogenesis hypothesis of depression posits (1) that neurogenesis in the subgranular zone of the dentate gyrus is regulated negatively by stressful experiences and positively by treatment with antidepressant drugs and (2) that alterations in the rate of neurogenesis play a fundamental role in the pathology and treatment of major depression. This hypothesis is supported by important experimental observations, but is challenged by equally compelling contradictory reports. This review summarizes the phenomenon of adult hippocampal neurogenesis, the initial and continued evidence leading to the development of the neurogenesis hypothesis of depression, and the recent studies that have disputed and/or qualified those findings, to conclude that it can be affected by stress and antidepressants under certain conditions, but that these effects do not appear in all cases of psychological stress, depression, and antidepressant treatment.
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Affiliation(s)
- Nicola D Hanson
- Laboratory of Neuropsychopharmacology, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Michael J Owens
- Laboratory of Neuropsychopharmacology, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA,Laboratory of Neuropsychopharmacology, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, 100 Woodruff Circle, Suite 4000, Atlanta, GA 30322, USA. Tel: +1 404 727 4059, Fax: +1 404 727 3233, E-mail:
| | - Charles B Nemeroff
- Department of Psychiatry and Behavioral Sciences, University of Miami School of Medicine, Miami, FL, USA
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129
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Surget A, Tanti A, Leonardo ED, Laugeray A, Rainer Q, Touma C, Palme R, Griebel G, Ibarguen-Vargas Y, Hen R, Belzung C. Antidepressants recruit new neurons to improve stress response regulation. Mol Psychiatry 2011; 16:1177-88. [PMID: 21537331 PMCID: PMC3223314 DOI: 10.1038/mp.2011.48] [Citation(s) in RCA: 337] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent research suggests an involvement of hippocampal neurogenesis in behavioral effects of antidepressants. However, the precise mechanisms through which newborn granule neurons might influence the antidepressant response remain elusive. Here, we demonstrate that unpredictable chronic mild stress in mice not only reduces hippocampal neurogenesis, but also dampens the relationship between hippocampus and the main stress hormone system, the hypothalamo-pituitary-adrenal (HPA) axis. Moreover, this relationship is restored by treatment with the antidepressant fluoxetine, in a neurogenesis-dependent manner. Specifically, chronic stress severely impairs HPA axis activity, the ability of hippocampus to modulate downstream brain areas involved in the stress response, the sensitivity of the hippocampal granule cell network to novelty/glucocorticoid effects and the hippocampus-dependent negative feedback of the HPA axis. Remarkably, we revealed that, although ablation of hippocampal neurogenesis alone does not impair HPA axis activity, the ability of fluoxetine to restore hippocampal regulation of the HPA axis under chronic stress conditions, occurs only in the presence of an intact neurogenic niche. These findings provide a mechanistic framework for understanding how adult-generated new neurons influence the response to antidepressants. We suggest that newly generated neurons may facilitate stress integration and that, during chronic stress or depression, enhancing neurogenesis enables a dysfunctional hippocampus to restore the central control on stress response systems, then allowing recovery.
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Affiliation(s)
- A Surget
- U930 Imaging and Brain, Inserm, Tours, France.
| | - A Tanti
- U930 Imaging and Brain, Inserm, Tours, France,Université François Rabelais, Tours, France
| | - E D Leonardo
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY, USA
| | - A Laugeray
- U930 Imaging and Brain, Inserm, Tours, France,Université François Rabelais, Tours, France
| | - Q Rainer
- U930 Imaging and Brain, Inserm, Tours, France,Université François Rabelais, Tours, France
| | - C Touma
- Research Group of Psychoneuroendocrinology, Max Planck Institute of Psychiatry, Munich, Germany
| | - R Palme
- Department of Biomedical Sciences/Biochemistry, University of Veterinary Medicine, Vienna, Austria
| | - G Griebel
- Exploratory Unit, Sanofi-Aventis, Chilly-Mazarin, France
| | - Y Ibarguen-Vargas
- U930 Imaging and Brain, Inserm, Tours, France,Université François Rabelais, Tours, France,Kavli Institute for Systems Neuroscience & Centre for the Biology of Memory, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - R Hen
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY, USA
| | - C Belzung
- U930 Imaging and Brain, Inserm, Tours, France,Université François Rabelais, Tours, France
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130
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Fuster-Matanzo A, Llorens-Martín M, de Barreda EG, Ávila J, Hernández F. Different susceptibility to neurodegeneration of dorsal and ventral hippocampal dentate gyrus: a study with transgenic mice overexpressing GSK3β. PLoS One 2011; 6:e27262. [PMID: 22073301 PMCID: PMC3207840 DOI: 10.1371/journal.pone.0027262] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 10/12/2011] [Indexed: 11/19/2022] Open
Abstract
Dorsal hippocampal regions are involved in memory and learning processes, while ventral areas are related to emotional and anxiety processes. Hippocampal dependent memory and behaviour alterations do not always come out in neurodegenerative diseases at the same time. In this study we have tested the hypothesis that dorsal and ventral dentate gyrus (DG) regions respond in a different manner to increased glycogen synthase kinase-3β (GSK3β) levels in GSK3β transgenic mice, a genetic model of neurodegeneration. Reactive astrocytosis indicate tissue stress in dorsal DG, while ventral area does not show that marker. These changes occurred with a significant reduction of total cell number and with a significantly higher level of cell death in dorsal area than in ventral one as measured by fractin-positive cells. Biochemistry analysis showed higher levels of phosphorylated GSK3β in those residues that inactivate the enzyme in hippocampal ventral areas compared with dorsal area suggesting that the observed susceptibility is in part due to different GSK3 regulation. Previous studies carried out with this animal model had demonstrated impairment in Morris Water Maze and Object recognition tests point out to dorsal hippocampal atrophy. Here, we show that two tests used to evaluate emotional status, the light–dark box and the novelty suppressed feeding test, suggest that GSK3β mice do not show any anxiety-related disorder. Thus, our results demonstrate that in vivo overexpression of GSK3β results in dorsal but not ventral hippocampal DG neurodegeneration and suggest that both areas do not behave in a similar manner in neurodegenerative processes.
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Affiliation(s)
- Almudena Fuster-Matanzo
- Centro de Biología Molecular “Severo Ochoa” (CSIC/UAM), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | - María Llorens-Martín
- Centro de Biología Molecular “Severo Ochoa” (CSIC/UAM), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | - Elena Gómez de Barreda
- Centro de Biología Molecular “Severo Ochoa” (CSIC/UAM), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | - Jesús Ávila
- Centro de Biología Molecular “Severo Ochoa” (CSIC/UAM), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
- CIBERNED, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, Madrid, Spain
| | - Félix Hernández
- Centro de Biología Molecular “Severo Ochoa” (CSIC/UAM), Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
- CIBERNED, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, Madrid, Spain
- * E-mail:
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131
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Schmidt B, Marrone DF, Markus EJ. Disambiguating the similar: the dentate gyrus and pattern separation. Behav Brain Res 2011; 226:56-65. [PMID: 21907247 DOI: 10.1016/j.bbr.2011.08.039] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 08/26/2011] [Indexed: 12/22/2022]
Abstract
The human hippocampus supports the formation of episodic memory without confusing new memories with old ones. To accomplish this, the brain must disambiguate memories (i.e., accentuate the differences between experiences). There is convergent evidence linking pattern separation to the dentate gyrus. Damage to the dentate gyrus reduces an organism's ability to differentiate between similar objects. The dentate gyrus has tenfold more principle cells than its cortical input, allowing for a divergence in information flow. Dentate gyrus granule neurons also show a very different pattern of representing the environment than "classic" place cells in CA1 and CA3, or grid cells in the entorhinal cortex. More recently immediate early genes have been used to "timestamp" activity of individual cells throughout the dentate gyrus. These data indicate that the dentate gyrus robustly differentiates similar situations. The degree of differentiation is non-linear, with even small changes in input inducing a near maximal response in the dentate. Furthermore this differentiation occurs throughout the dentate gyrus longitudinal (dorsal-ventral) axis. Conversely, the data point to a divergence in information processing between the dentate gyrus suprapyramidal and infrapyramidal blades possibly related to differences in organization within these regions. The accumulated evidence from different approaches converges to support a role for the dentate gyrus in pattern separation. There are however inconsistencies that may require incorporation of neurogenesis and hippocampal microcircuits into the currents models. They also suggest different roles for the dentate gyrus suprapyramidal and infrapyramidal blades, and the responsiveness of CA3 to dentate input.
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132
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Llorens-Martin M, Hernandez F, Avila J. Expression of frontotemporal dementia with parkinsonism associated to chromosome 17 tau induces specific degeneration of the ventral dentate gyrus and depressive-like behavior in mice. Neuroscience 2011; 196:215-27. [PMID: 21907761 DOI: 10.1016/j.neuroscience.2011.08.057] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 07/28/2011] [Accepted: 08/24/2011] [Indexed: 01/05/2023]
Abstract
When bearing certain frontotemporal dementia with parkinsonism (FTDP) mutations, overexpression of human tau resulted in a decrease of the dentate gyrus ventral blade, apparently due to a reduction in the proliferation of neuronal precursors and an increase in neuronal cell death. This degenerative process was accompanied by a dramatic increase in behavioral despair, as evident in the Porsolt swim test. Interestingly, we observed an increase in GABAergic innervation in the molecular layer of the dorsal dentate gyrus but not in the ventral domain. We suggest that this increase in GABAergic innervation reflects a compensatory neuroprotective response to the overexpression of toxic tau, which may prevent or delay degeneration in the dorsal blade of the dental gyrus. Finally, we suggest that this transgenic mouse, which overexpresses human FTPD tau, may serve as a useful model to study specific functions of the ventral dentate gyrus.
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Affiliation(s)
- M Llorens-Martin
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, Universidad Autónoma de Madrid, Campus Cantoblanco, 28049 Madrid, Spain
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133
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Wojtowicz JM. Adult neurogenesis. From circuits to models. Behav Brain Res 2011; 227:490-6. [PMID: 21893104 DOI: 10.1016/j.bbr.2011.08.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 08/05/2011] [Accepted: 08/06/2011] [Indexed: 10/17/2022]
Abstract
Our understanding of the hippocampus as a memory-encoding device is greatly helped by our knowledge of neuronal circuits and their plasticity. The trisynaptic hippocampal circuit carrying afferent input from the entorhinal cortex, controlled by a network of inhibitory interneurons and supplemented by modulatory subcortical inputs forms a platform for multiple forms of synaptic plastic mechanisms. Long-term potentiation of synaptic transmission in its various forms is an outstanding example of hippocampal ability to adapt to past neuronal activity. Adult neurogenesis is a profound plastic mechanism incorporating structural and functional changes that were previously thought to be present only in developing neural systems. These powerful forms of plasticity can mask experimental results by compensating for experimentally induced changes in the neurons or circuits. Circuit lesions have been one of the most common techniques in scientific investigations of the hippocampus. Although the effects of such lesions can be quite revealing and ground-breaking, in many cases the results are masked by compensatory mechanisms producing misleading results. This review will highlight such mechanisms and argue that the experimental results, in spite of their shortcomings, can be better understood when viewed in light of our knowledge of the neuronal circuitry, and with guidance by conceptual and computational models. Studies demonstrating a role of neurogenesis in pattern separation and memory interference are a good example of fruitful interaction between modeling and experimental approaches.
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134
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The timing for neuronal maturation in the adult hippocampus is modulated by local network activity. J Neurosci 2011; 31:7715-28. [PMID: 21613484 DOI: 10.1523/jneurosci.1380-11.2011] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The adult hippocampus continuously generates new cohorts of immature neurons with increased excitability and plasticity. The window for the expression of those unique properties in each cohort is determined by the time required to acquire a mature neuronal phenotype. Here, we show that local network activity regulates the rate of maturation of adult-born neurons along the septotemporal axis of the hippocampus. Confocal microscopy and patch-clamp recordings were combined to assess marker expression, morphological development, and functional properties in retrovirally labeled neurons over time. The septal dentate gyrus displayed higher levels of basal network activity and faster rates of newborn neuron maturation than the temporal region. Voluntary exercise enhanced network activity only in the temporal region and, in turn, accelerated neuronal development. Finally, neurons developing within a highly active environment exhibited a delayed maturation when their intrinsic electrical activity was reduced by the cell-autonomous overexpression of Kir2.1, an inward-rectifying potassium channel. Our findings reveal a novel type of activity-dependent plasticity acting on the timing of neuronal maturation and functional integration of newly generated neurons along the longitudinal axis of the adult hippocampus.
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135
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Snyder JS, Cameron HA. Could adult hippocampal neurogenesis be relevant for human behavior? Behav Brain Res 2011; 227:384-90. [PMID: 21736900 DOI: 10.1016/j.bbr.2011.06.024] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 06/02/2011] [Accepted: 06/20/2011] [Indexed: 12/21/2022]
Abstract
Although the function of adult neurogenesis is still unclear, tools for directly studying the behavioral role of new hippocampal neurons now exist in rodents. Since similar studies are impossible to do in humans, it is important to assess whether the role of new neurons in rodents is likely to be similar to that in humans. One feature of adult neurogenesis that varies tremendously across species is the number of neurons that are generated, so a key question is whether there are enough neurons generated in humans to impact function. In this review we examine neuroanatomy and circuit function in the hippocampus to ask how many granule neurons are needed to impact hippocampal function and then discuss what is known about numbers of new neurons produced in adult rats and humans. We conclude that relatively small numbers of neurons could affect hippocampal circuits and that the magnitude of adult neurogenesis in adult rats and humans is probably larger than generally believed.
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Affiliation(s)
- Jason S Snyder
- Unit on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Building 35/3C911, MSC3718, Bethesda, MD 20892, USA.
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136
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Complementary activation of hippocampal-cortical subregions and immature neurons following chronic training in single and multiple context versions of the water maze. Behav Brain Res 2011; 227:330-9. [PMID: 21736899 DOI: 10.1016/j.bbr.2011.06.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Revised: 05/31/2011] [Accepted: 06/20/2011] [Indexed: 11/22/2022]
Abstract
Neurobiological studies of memory typically involve single learning sessions that last minutes or days. In natural settings, however, animals are constantly learning. Here we investigated how several weeks of spatial water maze training influences subsequent activation of neocortical and hippocampal subregions, including adult-born neurons. Mice were either trained in a single context or in a variant of the task in which the spatial cues and platform location changed every 3 days, requiring constant new learning. On the final day, half of the mice in each training group were tested in a novel context and the other half were tested in their previous, familiar context. Two hours later mice were perfused to measure subregion-specific expression of the immediate-early gene zif268, a marker of neuronal activation. None of the training paradigms affected the magnitude of adult neurogenesis. However, different neuronal populations were activated depending on prior training history, final context novelty, or a combination of these 2 factors. The anterior cingulate cortex was more activated by novel context exposure, regardless of the type of prior training. The suprapyramidal blade of the dentate gyrus and region CA3 showed greater activation in mice trained in multiple contexts, primarily after exposure to a familiar context. In immature granule neurons, multiple context training enhanced activation regardless of final context novelty. CA1 showed no significant changes in zif268 expression across any training condition. In naïve control mice, training on the final day increased zif268 expression in CA3, CA1 and the anterior cingulate cortex, but not the dentate gyrus, relative to mice that remained in their cages (transport controls). Unexpectedly, immature granule cells showed a decrease in zif268 expression in naïve learners relative to transport controls. These findings suggest novel and complementary roles for hippocampal, neocortical, and immature neuronal populations in learning and memory.
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137
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Leuner B, Caponiti JM, Gould E. Oxytocin stimulates adult neurogenesis even under conditions of stress and elevated glucocorticoids. Hippocampus 2011; 22:861-8. [PMID: 21692136 DOI: 10.1002/hipo.20947] [Citation(s) in RCA: 165] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/17/2011] [Indexed: 12/20/2022]
Abstract
Oxytocin has been linked to social behavior, including social recognition, pair bonding and parenting, but its potential role in promoting neuronal growth has not been investigated. We show here that oxytocin, but not vasopressin, stimulates both cell proliferation and adult neurogenesis in the hippocampus of rats. Oxytocin is also capable of stimulating adult neurogenesis in rats subjected to glucocorticoid administration or cold water swim stress. These findings suggest that oxytocin stimulates neuronal growth and may protect against the suppressive effects of stress hormones on hippocampal plasticity.
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Affiliation(s)
- Benedetta Leuner
- Department of Psychology, Neuroscience Institute, Princeton University, Princeton, New Jersey 08544, USA
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138
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Winocur G, Becker S, Luu P, Rosenzweig S, Wojtowicz JM. Adult hippocampal neurogenesis and memory interference. Behav Brain Res 2011; 227:464-9. [PMID: 21669236 DOI: 10.1016/j.bbr.2011.05.032] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 05/06/2011] [Accepted: 05/28/2011] [Indexed: 01/06/2023]
Abstract
Rats, subjected to low-dose irradiation that suppressed hippocampal neurogenesis, or a sham treatment, were administered a visual discrimination task under conditions of high, or low interference. Half of the rats engaged in running activity and the other half did not. In the non-runners, there was no effect of irradiation on learning, or remembering the discrimination response under low interference, but irradiation treatment increased their susceptibility to interference, resulting in loss of memory for the previously learned discrimination. Irradiated rats that engaged in running activity exhibited increased neuronal growth and protection from memory impairment. The results, which show that hippocampal cells generated in adulthood play a role in differentiating between conflicting, context-dependent memories, provide further evidence of the importance of neurogenesis in hippocampus-sensitive memory tasks. The results are consistent with computational models of hippocampal function that specify a central role for neurogenesis in the modulation of interfering influences during learning and memory.
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Affiliation(s)
- Gordon Winocur
- Rotman Research Institute, Baycrest Centre, 3560 Bathurst Street, Toronto, Ontario M6A 2E1, Canada.
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139
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Hinman JR, Penley SC, Long LL, Escabí MA, Chrobak JJ. Septotemporal variation in dynamics of theta: speed and habituation. J Neurophysiol 2011; 105:2675-86. [DOI: 10.1152/jn.00837.2010] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Theta (6–12 Hz) field potentials and the synchronization (coherence) of these potentials present neural network indices of hippocampal physiology. Theta signals within the hippocampal formation may reflect alterations in sensorimotor integration, the flow of sensory input, and/or distinct cognitive operations. While the power and coherence of theta signals vary across lamina within the septal hippocampus, limited information is available about variation in these indices across the septotemporal (long) or areal axis. The present study examined the relationship of locomotor speed to theta indices at CA1 and dentate gyrus (DG) sites across the septotemporal axis as well as in the entorhinal cortex. Our findings demonstrate the dominant relationship of speed to theta indices at septal sites. This relationship diminished systematically with distance from the septal pole of the hippocampus at both CA1 and DG sites. While theta power at entorhinal sites varied in relation to speed, there were no differences across the areal axis of the entorhinal cortex. Locomotor speed was also related to changes in theta coherence along the septotemporal axis as well as between the hippocampus and entorhinal cortex. In addition to the speed-related variation, we observed a decrease in theta power at more temporal hippocampal sites over repeated behavioral testing within a single day that was not observed at septal sites. The results outline a dynamic and distributed pattern of network activity across the septotemporal axis of the hippocampus in relation to locomotor speed and recent past experience.
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Affiliation(s)
| | | | | | - Monty A. Escabí
- Departments of 1Psychology,
- Biomedical Engineering, and
- Electrical and Computer Engineering, University of Connecticut, Storrs, Connecticut
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140
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Ming GL, Song H. Adult neurogenesis in the mammalian brain: significant answers and significant questions. Neuron 2011; 70:687-702. [PMID: 21609825 PMCID: PMC3106107 DOI: 10.1016/j.neuron.2011.05.001] [Citation(s) in RCA: 1872] [Impact Index Per Article: 144.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2011] [Indexed: 12/11/2022]
Abstract
Adult neurogenesis, a process of generating functional neurons from adult neural precursors, occurs throughout life in restricted brain regions in mammals. The past decade has witnessed tremendous progress in addressing questions related to almost every aspect of adult neurogenesis in the mammalian brain. Here we review major advances in our understanding of adult mammalian neurogenesis in the dentate gyrus of the hippocampus and from the subventricular zone of the lateral ventricle, the rostral migratory stream to the olfactory bulb. We highlight emerging principles that have significant implications for stem cell biology, developmental neurobiology, neural plasticity, and disease mechanisms. We also discuss remaining questions related to adult neural stem cells and their niches, underlying regulatory mechanisms, and potential functions of newborn neurons in the adult brain. Building upon the recent progress and aided by new technologies, the adult neurogenesis field is poised to leap forward in the next decade.
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Affiliation(s)
- Guo-Li Ming
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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141
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Tan YF, Rosenzweig S, Jaffray D, Wojtowicz JM. Depletion of new neurons by image guided irradiation. Front Neurosci 2011; 5:59. [PMID: 21541259 PMCID: PMC3083759 DOI: 10.3389/fnins.2011.00059] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 04/07/2011] [Indexed: 01/25/2023] Open
Abstract
Ionizing radiation continues to be a relevant tool in both imaging and the treatment of cancer. Experimental uses of focal irradiation have recently been expanded to studies of new neurons in the adult brain. Such studies have shown cognitive deficits following radiation treatment and raised caution as to possible unintentional effects that may occur in humans. Conflicting outcomes of the effects of irradiation on adult neurogenesis suggest that the effects are either transient or permanent. In this study, we used an irradiation apparatus employed in the treatment of human tumors to assess radiation effects on rat neurogenesis. For subjects we used adult male rats (Sprague-Dawley) under anesthesia. The irradiation beam was directed at the hippocampus, a center for learning and memory, and the site of neurogenic activity in adult brain. The irradiation was applied at a dose-rate 0.6 Gy/min for total single-fraction, doses ranging from 0.5 to 10.0 Gy. The animals were returned to home cages and recovered with no sign of any side effects. The neurogenesis was measured either 1 week or 6 weeks after the irradiation. At 1 week, the number of neuronal progenitors was reduced in a dose-dependent manner with the 50% reduction at 0.78 Gy. The dose–response curve was well fitted by a double exponential suggesting two processes. Examination of the tissue with quantitative immunohistochemistry revealed a dominant low-dose effect on neuronal progenitors resulting in 80% suppression of neurogenesis. This effect was partially reversible, possibly due to compensatory proliferation of the remaining precursors. At higher doses (>5 Gy) there was additional, nearly complete block of neurogenesis without compensatory proliferation. We conclude that notwithstanding the usefulness of irradiation for experimental purposes, the exposure of human subjects to doses often used in radiotherapy treatment could be damaging and cause cognitive impairments.
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Affiliation(s)
- Y-F Tan
- Department of Physiology, Faculty of Medicine, University of Toronto Toronto, ON, Canada
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142
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Working memory task decreases the survival of newly born neurons in hippocampus. Neurobiol Learn Mem 2011; 95:239-47. [DOI: 10.1016/j.nlm.2010.11.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2010] [Revised: 10/27/2010] [Accepted: 11/19/2010] [Indexed: 11/18/2022]
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143
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Epp JR, Haack AK, Galea LAM. Activation and survival of immature neurons in the dentate gyrus with spatial memory is dependent on time of exposure to spatial learning and age of cells at examination. Neurobiol Learn Mem 2011; 95:316-25. [PMID: 21216298 DOI: 10.1016/j.nlm.2011.01.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 12/02/2010] [Accepted: 01/03/2011] [Indexed: 11/27/2022]
Abstract
Neurogenesis continues to occur throughout life in the dentate gyrus of the hippocampus and may be related to hippocampus-dependent learning. We have recently reported that there is an enhancement of neurogenesis in the hippocampus only when BrdU is administered 6 days prior to starting spatial training but not when training started either 1 day or 11 days following BrdU administration. In that study, all rats were perfused on day 16 after BrdU injection in order to compare cells of the same age (i.e. 16 day old cells) and thus the survival time after learning was different between groups. This study was designed to address whether the amount of time that passed following training could also contribute to the effects of spatial learning on hippocampal neurogenesis and whether there was differential new neuron activation in response to spatial learning that depended on the age of new cells at the time of spatial learning. Here we tested whether a survival period of 5 days following spatial learning at either 1-5, 6-10 or 11-15 days following BrdU administration would alter cell survival and/or activation of new neurons. Our results indicate that 5 days after training in the Morris water task cell survival is unaltered by training on days 1-5, increased by training at days 6-10 and decreased when training occurs on days 11-15. Furthermore spatial learners trained on days 6-10 or 11-15 show greater activation of new neurons compared to cue-trained rats during a probe trial 5 days after training. In addition, rats trained on the spatial task on days 11-15 had a greater number of activated new neurons compared to rats trained on the spatial task on days 6-10. These results suggest there is a gradual removal of older BrdU-labeled new neurons following spatial learning perhaps due to a competitive interaction with a population of younger BrdU-labeled new neurons.
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Affiliation(s)
- Jonathan R Epp
- Department of Psychology, Graduate Program in Neuroscience, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada
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144
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Castilla-Ortega E, Pedraza C, Estivill-Torrús G, Santín LJ. When is adult hippocampal neurogenesis necessary for learning? Evidence from animal research. Rev Neurosci 2011; 22:267-83. [DOI: 10.1515/rns.2011.027] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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145
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Epp J, Scott N, Galea L. Strain differences in neurogenesis and activation of new neurons in the dentate gyrus in response to spatial learning. Neuroscience 2011; 172:342-54. [DOI: 10.1016/j.neuroscience.2010.10.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 10/09/2010] [Accepted: 10/11/2010] [Indexed: 10/18/2022]
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146
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Barry DN, Commins S. Imaging spatial learning in the brain using immediate early genes: insights, opportunities and limitations. Rev Neurosci 2011; 22:131-42. [DOI: 10.1515/rns.2011.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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147
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Burger C. Region-specific genetic alterations in the aging hippocampus: implications for cognitive aging. Front Aging Neurosci 2010; 2:140. [PMID: 21048902 PMCID: PMC2967426 DOI: 10.3389/fnagi.2010.00140] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 08/17/2010] [Indexed: 01/31/2023] Open
Abstract
Aging is associated with cognitive decline in both humans and animals and of all brain regions, the hippocampus appears to be particularly vulnerable to senescence. Age-related spatial learning deficits result from alterations in hippocampal connectivity and plasticity. These changes are differentially expressed in each of the hippocampal fields known as cornu ammonis 1 (CA1), cornu ammonis 3 (CA3), and the dentate gyrus. Each sub-region displays varying degrees of susceptibility to aging. For example, the CA1 region is particularly susceptible in Alzheimer's disease while the CA3 region shows vulnerability to stress and glucocorticoids. Further, in animals, aging is the main factor associated with the decline in adult neurogenesis in the dentate gyrus. This review discusses the relationship between region-specific hippocampal connectivity, morphology, and gene expression alterations and the cognitive deficits associated with senescence. In particular, data are reviewed that illustrate how the molecular changes observed in the CA1, CA3, and dentate regions are associated with age-related learning deficits. This topic is of importance because increased understanding of how gene expression patterns reflect individual differences in cognitive performance is critical to the process of identifying new and clinically useful biomarkers for cognitive aging.
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Affiliation(s)
- Corinna Burger
- Department of Neurology, Medical Sciences Center, University of WisconsinMadison, USA
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148
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Christensen T, Bisgaard C, Nielsen H, Wiborg O. Transcriptome differentiation along the dorso–ventral axis in laser-captured microdissected rat hippocampal granular cell layer. Neuroscience 2010; 170:731-41. [DOI: 10.1016/j.neuroscience.2010.07.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 07/02/2010] [Accepted: 07/06/2010] [Indexed: 12/31/2022]
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149
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Sidor MM, Amath A, MacQueen G, Foster JA. A developmental characterization of mesolimbocortical serotonergic gene expression changes following early immune challenge. Neuroscience 2010; 171:734-46. [PMID: 20816924 DOI: 10.1016/j.neuroscience.2010.08.060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 08/25/2010] [Accepted: 08/30/2010] [Indexed: 12/15/2022]
Abstract
An immunogenic challenge during early postnatal development leads to long-term changes in behavioural and physiological measures reflecting enhanced emotionality and anxiety. Altered CNS serotonin (5-HT) signalling during the third postnatal week is thought to modify the developing neurocircuitry governing anxiety-like behaviour. Changes in 5-HT signalling during this time window may underlie increased emotionality reported in early immune challenge rodents. Here we examine both the spatial and temporal profile of 5-HT related gene expression, including 5HT1A, 2A, 2C receptors, the 5-HT transporter (5HTT), and tryptophan hydroxylase 2 (TPH2) during early development (postnatal day [P]14, P17, P21, P28) in mice challenged with lipopolysaccharide (LPS) during the first postnatal week. Expression levels were measured using in situ hybridization in regions associated with mediating emotive behaviours: the dorsal raphe (DR), hippocampus, amygdala, and prefrontal cortex (PFC). Increased TPH2 and 5HTT expression in the ventrolateral region of the DR of LPS-mice accompanied decreased expression of ventral DR 5HT1A and dorsal DR 5HTT. In the forebrain, 5HT1A and 2A receptors were increased, whereas 5HT2C receptors were decreased in the hippocampus. Decreased mRNA expression of 5HT2C was detected in the amygdala and PFC of LPS-treated pups; 5HT1A was increased in the PFC. The majority of these changes were restricted to P14-21. These transient changes in 5-HT expression coincide with the critical time window in which 5-HT disturbance leads to permanent modification of anxiety-related behaviours. This suggests that alterations in CNS 5-HT during development may underlie the enhanced emotionality associated with an early immune challenge.
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Affiliation(s)
- M M Sidor
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
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150
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Lloyd SA, Balest ZR, Corotto FS, Smeyne RJ. Cocaine selectively increases proliferation in the adult murine hippocampus. Neurosci Lett 2010; 485:112-6. [PMID: 20817079 DOI: 10.1016/j.neulet.2010.08.080] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 08/20/2010] [Accepted: 08/27/2010] [Indexed: 11/17/2022]
Abstract
Cocaine abuse continues to be a significant problem in the USA and elsewhere. Cocaine is an indirect agonist for dopamine, norepinephrine and serotonin with numerous potential downstream effects, including processes and signals associated with adult neurogenesis. Since drug addiction is associated with brain plasticity, we hypothesized that cocaine exposure would alter cellular proliferation in two adult neurogenic regions (the subventricular and subgranular zones). We used bromodeoxyuridine (BrdU) to track newly generated cells in the brains of adult mice after chronic cocaine or saline exposures. No differences were found in the number or migration patterns of BrdU-labeled cells in the forebrain neurogenic areas. However, cocaine produced a significant increase in the number of hippocampal BrdU-labeled cells.
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Affiliation(s)
- Steven A Lloyd
- Department of Psychology, North Georgia College & State University, 82 College Circle, Dunlap Hall, Room 202B, Dahlonega, GA 30597, USA.
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