151
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Aztiria E, Capodieci G, Arancio L, Leanza G. Extensive training in a maze task reduces neurogenesis in the adult rat dentate gyrus probably as a result of stress. Neurosci Lett 2007; 416:133-7. [PMID: 17317003 DOI: 10.1016/j.neulet.2007.01.069] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 01/23/2007] [Accepted: 01/27/2007] [Indexed: 11/27/2022]
Abstract
It has recently been shown that hippocampal neurogenesis can be modulated either directly or indirectly by ascending cholinergic inputs from the basal forebrain. In the present work, we sought to address whether extended training in a spatial navigation task would affect hippocampal neurogenesis in the presence of a severe and selective cholinergic depletion. Young female rats received stereotaxic injections of the immunotoxin 192 IgG-saporin into the basal forebrain nuclei and/or the cerebellar cortex. Starting from 4 to 5 weeks post-lesion, and for the subsequent 2 weeks, the animals were trained on paradigms of reference and working memory in the water maze and received single daily i.p. injections of bromodeoxyuridine (BrdU) at the end of each testing session. In line with previous observations, a dramatic 80% decrease in neuron proliferation was seen in the dentate gyrus of lesioned animals, as compared to vehicle-injected or intact controls. Interestingly, however, rats subjected to maze training over 2 weeks, irrespective of their learning success, exhibited significantly fewer newborn neurons than matched controls with no maze exposure. Thus, at least for the type of task used here, which has previously been shown to impose a certain degree of stress, extended training and learning does not appear to affect proliferation in the dentate gyrus.
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Affiliation(s)
- E Aztiria
- BRAIN Centre for Neuroscience, Department of Physiology and Pathology, University of Trieste, Via Fleming 22, 34127 Trieste, Italy
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152
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Fritzen S, Schmitt A, Köth K, Sommer C, Lesch KP, Reif A. Neuronal nitric oxide synthase (NOS-I) knockout increases the survival rate of neural cells in the hippocampus independently of BDNF. Mol Cell Neurosci 2007; 35:261-71. [PMID: 17459722 DOI: 10.1016/j.mcn.2007.02.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 02/27/2007] [Accepted: 02/28/2007] [Indexed: 01/17/2023] Open
Abstract
Investigations regarding the regulation of adult neurogenesis, i.e., the generation of new neurons from progenitor cells, have revealed a high degree of complexity. Although the pleiotropic messenger molecule nitric oxide (NO) has been suggested to modulate adult neurogenesis, the evidence is inconclusive due to the presence of different NO synthase isoforms in the brain. We therefore investigated whether stem cell proliferation or survival is altered in mice lacking neuronal nitric oxide synthase (NOS-I) or both endothelial and neuronal NOS (NOS-I/-III double knockout). While proliferation of neural stem cells was only numerically, but not significantly increased in NOS-I knockdown animals, the survival of newly formed neurons was substantially higher in NOS-I-deficient mice. In contrast, NOS-I/-III double knockout had significantly decreased survival rates. QRT-PCR in NOS-I-deficient mice revealed neither NOS-III upregulation compensating for the loss of NOS-I, nor alterations in VEGF levels as found in NOS-III-deficient animals. As changes in BDNF expression or protein levels were observed in the cortex, cerebellum and striatum, but not the hippocampus, the increase in stem cell survival appears not to be due to a BDNF mediated mechanism. Finally, NOS-I containing neurons in the dentate gyrus are rare and not localized close to progenitor cells, rendering direct NO effects on these cells unlikely. In conclusion, we suggest that NO predominantly inhibits the survival of new-born cells, by an indirect mechanism not involving BDNF or VEGF. Together, these results emphasize the important role of the different NOS isoforms with respect to adult neurogenesis.
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Affiliation(s)
- Sabrina Fritzen
- Molecular and Clinical Psychobiology, Department of Psychiatry and Psychotherapy Josef-Schneider-Str. 11, Julius-Maximilians-University Würzburg, Füchsleinstr. 15, D-97080 Würzburg, Germany
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153
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154
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Henninger N, Feldmann RE, Fütterer CD, Schrempp C, Maurer MH, Waschke KF, Kuschinsky W, Schwab S. Spatial learning induces predominant downregulation of cytosolic proteins in the rat hippocampus. GENES BRAIN AND BEHAVIOR 2007; 6:128-40. [PMID: 16643511 DOI: 10.1111/j.1601-183x.2006.00239.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Spatial learning is known to depend on protein synthesis in the hippocampus. Whereas the role of the hippocampus in spatial memory is established, the biochemical and molecular mechanisms underlying this process are poorly understood. To comprehend the complex pattern of protein expression induced by spatial learning, we analyzed alterations in the rat hippocampus proteome after 7 days of spatial learning in the Morris water maze. Forty Wistar rats were randomized into two groups. Animals of group A learned to localize a hidden platform in the water maze. Animals of group B served as controls and spent exactly the same time in the water maze as animals of group A. However, no platform was used in this test and the rats could not learn to localize the target. After the last trial, hydrophilic proteins from the hippocampus were isolated. A proteome-wide study was performed, based on two-dimensional gel electrophoresis and mass spectrometry. Compared with non-learning animals, 53 (70%) proteins were downregulated and 23 (30%) proteins were upregulated after 7 days in rats with spatial learning. The overall changes in protein expression, as quantified by the induction factor, ranged from -1.62 (downregulation to 62%) to 2.10 (upregulation by 110%) compared with controls (100%). Most identified proteins exhibit known functions in vesicle transport, cytoskeletal architecture, and metabolism as well as neurogenesis. These findings indicate that learning in the Morris water maze has a morphological correlate on the proteome level in the hippocampus.
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Affiliation(s)
- N Henninger
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.
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155
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Kronenberg G, Lippoldt A, Kempermann G. Two genetic rat models of arterial hypertension show different mechanisms by which adult hippocampal neurogenesis is increased. Dev Neurosci 2007; 29:124-33. [PMID: 17148955 DOI: 10.1159/000096217] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 03/28/2006] [Indexed: 12/29/2022] Open
Abstract
To investigate strain differences and genetic effects on different aspects of neurogenesis, we compared young adult spontaneously hypertensive/hyperactive rats (SHR) and stroke-prone SHR (SHRSP) with the genetic control WKY strain. In both hypertensive/hyperactive strains, the number of newly generated neurons and the number of lineage-determined cells as detected by doublecortin (DCX) immunoreactivity were significantly increased. SHRSP had significantly more DCX-positive cells than the other groups. Whereas cell proliferation as measured by Ki67 expression was increased in SHR, we found no difference between SHRSP and WKY. In summary, we found increased net neurogenesis in both hypertensive/hyperactive strains. However, this phenotype was based on different mechanisms in the course of neuronal development: cell proliferation in SHR and cell survival in SHRSP. In addition, we found that within strains the number of DCX-positive cells was not predictive of the net number of new neurons and that the increase in neurogenesis was not significantly correlated with blood pressure in SHR and WKY. However, in both SHR and SHRSP, cell proliferation showed an association with blood pressure recordings.
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Affiliation(s)
- Golo Kronenberg
- Max Delbruck Center for Molecular Medicine (MDC) Berlin-Buch, Germany
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156
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Nikolakopoulou AM, Dermon CR, Panagis L, Pavlidis M, Stewart MG. Passive avoidance training is correlated with decreased cell proliferation in the chick hippocampus. Eur J Neurosci 2007; 24:2631-42. [PMID: 17100851 DOI: 10.1111/j.1460-9568.2006.05133.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One-trial passive avoidance learning (PAL), where the aversive stimulus is the bitter-tasting substance methylanthranilate (MeA), affects neuronal and synaptic plasticity in learning-related areas of day-old domestic chicks (Gallus domesticus). Here, cell proliferation was examined in the chick forebrain by using 5-bromo-2-deoxyuridine (BrdU) at 24 h and 9 days after PAL. At 24 h post-BrdU injection, there was a significant reduction in labelling in MeA-trained chicks in both the dorsal hippocampus and area parahippocampalis, in comparison to controls. Moreover, double-immunofluorescence labelling for BrdU and the nuclear neuronal marker (NeuN) showed a reduction of neuronal cells in the dorsal hippocampus of the MeA-trained group compared with controls (35 and 49%, respectively). There was no difference in BrdU labelling in hippocampal regions between trained and control groups of chicks at 9 days post-BrdU injection; however, the number of BrdU-labelled cells was considerably lower than at 24 h post-BrdU injection, possibly due to migration of cells within the telencephalon rather than cell loss as apoptotic analyses at 24 h and 9 days post-BrdU injection did not demonstrate differences in cell death between treatment groups. Cortisol levels increased in the chick hippocampus of MeA-trained birds 20 min after PAL, suggesting the possibility of a stress-related mechanism of cell proliferation reduction in the hippocampus. In contrast to hippocampal areas, the olfactory bulb, an area strongly stimulated by the strong-smelling MeA, showed increased cell genesis in comparison to controls at both 24 h and 9 days post-training.
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157
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Bruel-Jungerman E, Rampon C, Laroche S. Adult Hippocampal Neurogenesis, Synaptic Plasticity and Memory: Facts and Hypotheses. Rev Neurosci 2007; 18:93-114. [PMID: 17593874 DOI: 10.1515/revneuro.2007.18.2.93] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The demonstration that progenitor cells in regions of the adult mammalian brain such as the dentate gyrus of the hippocampus can undergo mitosis and generate new cells that differentiate into functionally integrated neurons throughout life has marked a new era in neuroscience. In recent years, a wide range of investigations has been directed at understanding the physiological mechanisms and functional relevance of this form of brain plasticity. Our current knowledge of adult hippocampal neurogenesis indicates that the production of new cells in the brain follows a multi-step process during which newborn cells are submitted to various regulatory factors that influence cell proliferation, maturation, fate determination and survival. As details of the dynamics of morphological maturation and functional integration of newborn neurons in corticohippocampal circuits have become clearer, an increasing number of studies have examined how environmental and/or behavioural factors can modulate neurogenesis and affect hippocampal-dependent learning and memory. In this article we present an overview of recent literature that relates neurogenesis to hippocampal function on the basis of correlative studies investigating the modulation of neurogenesis by learning and behavioural experience, and the consequences of the loss of hippocampal neurogenesis for memory function. We also highlight experimental evidence that immature neurons exhibit unique electrophysiological characteristics and therefore may constitute a specific cell population particularly inclined to undergo activity-dependent plasticity. Moreover, we review recent work that reveals an unsuspected mechanistic link between synaptic plasticity and the proliferation and survival of new hippocampal neurons. From the present background of research, we argue that the incorporation of functional adult-generated neurons into existing neural networks provides a higher capacity for plasticity, which may favour the encoding and storage of certain types of memories. Depending on their birth date and maturation stage, new neurons might be implicated in the encoding/storage process of the task at hand or may help future learning experience. Finally, we highlight critical issues to be addressed in order to decipher the exact contribution of newly generated neurons to cognitive functions.
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Affiliation(s)
- Elodie Bruel-Jungerman
- Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, CNRS UMR 8620, University Paris-Sud, Orsay, France.
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158
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Leuner B, Waddell J, Gould E, Shors TJ. Temporal discontiguity is neither necessary nor sufficient for learning-induced effects on adult neurogenesis. J Neurosci 2006; 26:13437-42. [PMID: 17192426 PMCID: PMC3374596 DOI: 10.1523/jneurosci.2781-06.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 11/16/2006] [Accepted: 11/17/2006] [Indexed: 11/21/2022] Open
Abstract
Some, but not all, types of learning and memory can influence neurogenesis in the adult hippocampus. Trace eyeblink conditioning has been shown to enhance the survival of new neurons, whereas delay eyeblink conditioning has no such effect. The key difference between the two training procedures is that the conditioning stimuli are separated in time during trace but not delay conditioning. These findings raise the question of whether temporal discontiguity is necessary for enhancing the survival of new neurons. Here we used two approaches to test this hypothesis. First, we examined the influence of a delay conditioning task in which the duration of the conditioned stimulus (CS) was increased nearly twofold, a procedure that critically engages the hippocampus. Although the CS and unconditioned stimulus are contiguous, this very long delay conditioning procedure increased the number of new neurons that survived. Second, we examined the influence of learning the trace conditioned response (CR) after having acquired the CR during delay conditioning, a procedure that renders trace conditioning hippocampal-independent. In this case, trace conditioning did not enhance the survival of new neurons. Together, these results demonstrate that associative learning increases the survival of new neurons in the adult hippocampus, regardless of temporal contiguity.
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Affiliation(s)
- Benedetta Leuner
- Department of Psychology, Princeton University, Princeton, New Jersey 08544, and
| | - Jaylyn Waddell
- Department of Psychology and Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854
| | - Elizabeth Gould
- Department of Psychology, Princeton University, Princeton, New Jersey 08544, and
| | - Tracey J. Shors
- Department of Psychology and Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854
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159
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Wolf SA, Kronenberg G, Lehmann K, Blankenship A, Overall R, Staufenbiel M, Kempermann G. Cognitive and physical activity differently modulate disease progression in the amyloid precursor protein (APP)-23 model of Alzheimer's disease. Biol Psychiatry 2006; 60:1314-23. [PMID: 16806094 DOI: 10.1016/j.biopsych.2006.04.004] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Revised: 12/08/2005] [Accepted: 04/12/2006] [Indexed: 12/21/2022]
Abstract
BACKGROUND In aging mice, activity maintains hippocampal plasticity and adult hippocampal neurogenesis at a level corresponding to a younger age. Here we studied whether physical exercise and environmental enrichment would also affect brain plasticity in a mouse model of Alzheimer's disease (AD). METHODS Amyloid precursor protein (APP)-23 mice were housed under standard or enriched conditions or in cages equipped with a running wheel. We assessed beta-amyloid plaque load, adult hippocampal neurogenesis, spatial learning, and mRNA levels of trophic factors in the brain. RESULTS Despite stable beta-amyloid plaque load, enriched-living mice showed improved water maze performance, an up-regulation of hippocampal neurotrophin (NT-3) and brain-derived neurotrophic factor (BDNF) and increased hippocampal neurogenesis. In contrast, despite increased bodily fitness, wheel-running APP23 mice showed no change in spatial learning and no change in adult hippocampal neurogenesis but a down-regulation of hippocampal and cortical growth factors. CONCLUSIONS We conclude that structural and molecular prerequisites for activity-dependent plasticity are preserved in mutant mice with an AD-like pathology. Our study might help explain benefits of activity for the aging brain but also demonstrates differences between physical and more cognitive activity. It also suggests a possible cellular correlate for the dissociation between structural and functional pathology often found in AD.
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Affiliation(s)
- Susanne A Wolf
- Max Delbrück Center for Molecular Medicine, Berlin-Buch, Charité University Medicine, Berlin, Germany
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160
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Mandairon N, Sacquet J, Garcia S, Ravel N, Jourdan F, Didier A. Neurogenic correlates of an olfactory discrimination task in the adult olfactory bulb. Eur J Neurosci 2006; 24:3578-88. [PMID: 17229106 DOI: 10.1111/j.1460-9568.2006.05235.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In the main olfactory bulb, stimuli are coded within the spatio-temporal pattern of mitral cells' activity. Granule cells are interneurons that shape the mitral cells' activity, and are continuously generated in the adult main olfactory bulb. However, the role of granule cell renewal remains elusive. We show here that an associative olfactory discrimination task reduces the survival of newborn neurons. However, when the olfactory task involves perceptually related odorants, the learning process is slower and does not induce such a reduction in the number of new neurons. Mapping newborn cells within the granule cell layer of the main olfactory bulb reveals a clustered distribution that evolves with learning as a function of odorant similarity and partly overlaps with the immediate-early gene Zif268 expression pattern. These data provide insight into the functional mechanisms underlying olfactory discrimination learning, and promote the importance of neurogenesis as a cellular basis for the restructuring of odor images in the main olfactory bulb.
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Affiliation(s)
- Nathalie Mandairon
- Laboratoire de Neurosciences et Systèmes Sensoriels, CNRS UMR 5020, Université Claude Bernard Lyon1, 50 avenue Tony Garnier, 69366, LYON cedex 07, France.
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161
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Variability of doublecortin-associated dendrite maturation in adult hippocampal neurogenesis is independent of the regulation of precursor cell proliferation. BMC Neurosci 2006; 7:77. [PMID: 17105671 PMCID: PMC1657022 DOI: 10.1186/1471-2202-7-77] [Citation(s) in RCA: 298] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Accepted: 11/15/2006] [Indexed: 11/28/2022] Open
Abstract
Background In the course of adult hippocampal neurogenesis most regulation takes place during the phase of doublecortin (DCX) expression, either as pro-proliferative effect on precursor cells or as survival-promoting effect on postmitotic cells. We here obtained quantitative data about the proliferative population and the dynamics of postmitotic dendrite development during the period of DCX expression. The question was, whether any indication could be obtained that the initiation of dendrite development is timely bound to the exit from the cell cycle. Alternatively, the temporal course of morphological maturation might be subject to additional regulatory events. Results We found that (1) 20% of the DCX population were precursor cells in cell cycle, whereas more than 70% were postmitotic, (2) the time span until newborn cells had reached the most mature stage associated with DCX expression varied between 3 days and several weeks, (3) positive or negative regulation of precursor cell proliferation did not alter the pattern and dynamics of dendrite development. Dendrite maturation was largely independent of close contacts to astrocytes. Conclusion These data imply that dendrite maturation of immature neurons is initiated at varying times after cell cycle exit, is variable in duration, and is controlled independently of the regulation of precursor cell proliferation. We conclude that in addition to the major regulatory events in cell proliferation and selective survival, additional micro-regulatory events influence the course of adult hippocampal neurogenesis.
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162
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Mohapel P, Mundt-Petersen K, Brundin P, Frielingsdorf H. Working memory training decreases hippocampal neurogenesis. Neuroscience 2006; 142:609-13. [PMID: 16962715 DOI: 10.1016/j.neuroscience.2006.07.033] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 06/21/2006] [Accepted: 07/03/2006] [Indexed: 11/29/2022]
Abstract
The relationship between adult hippocampal neurogenesis and cognition appears more complex than suggested by early reports. We aimed to determine if the duration and task demands of spatial memory training differentially affect hippocampal neurogenesis. Adult male rats were trained in the Morris water maze in a reference memory task for 4 days, or alternatively working memory for either 4 or 14 days. Four days of maze training did not impact neurogenesis regardless of whether reference or working memory paradigms were used. Interestingly, 2 weeks of working memory training using a hidden platform resulted in fewer newborn hippocampal neurons compared with controls that received either cue training or no maze exposure. Stress is a well-established negative regulator of hippocampal neurogenesis. We found that maze training in general, and a working memory task in particular, increased levels of circulating corticosterone after 4 days of training. Our study indicates that working memory training over a prolonged period of time reduces neurogenesis, and this reduction may partially be mediated by increased stress.
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Affiliation(s)
- P Mohapel
- Neuronal Survival Unit, Department of Experimental Medical Science, Wallenberg Neuroscience Center, BMC A10, 221 84 Lund, Sweden
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163
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Carrasco C, Vicens P, Redolat R. Neuroprotective effects of behavioural training and nicotine on age-related deficits in spatial learning. Behav Pharmacol 2006; 17:441-52. [PMID: 16940765 DOI: 10.1097/00008877-200609000-00010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Studies in humans and animals show a clear decline in spatial memory with age and several approaches have been adopted to alleviate this impairment. The purpose of our review is to assess the studies that have suggested the possible neuroprotective actions of behavioural training and nicotine-applied both independently and in conjunction-on age-related deficits in spatial learning. Both spatial pretraining and nonspatial experiences influence an animal's performance in spatial tasks. In aged rats, the experience of training in the water maze task increases the number of newly generated neurons in the hippocampus. The neuroprotective effects of nicotine have been demonstrated in both in-vitro and in-vivo models, although the molecular mechanisms underlying these actions are not yet fully understood. It had been concluded in different studies that nicotine can improve, impair or have no effect on performance in the water maze. Neurobiological data also suggest an interaction between nicotine and prior experience in complex tasks, although few studies have raised the question of whether nicotine treatment and training in spatial tasks may contribute in an interactive manner to alleviate spatial cognition impairment associated with the ageing process. Different findings suggest that past experience could be a confounding variable in longitudinal studies that aim to evaluate the neuroprotective effects of nicotine on age-related deficits in spatial learning.
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Affiliation(s)
- Carmen Carrasco
- Department of Psychobiology, Faculty of Psychology, University of Valencia, Blasco Ibañez 21, Valencia 46010, Spain
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164
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Abstract
During the past several years, evidence has accumulated suggesting a relationship between newly born cells in the hippocampus and various types of learning and memory. However, most of the evidence is correlational and some of it does not agree. This review discusses both sides of this issue, considering the effects of learning on the production of new neurons in the dentate gyrus and the question of whether newly born cells participate in learning and memory.
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Affiliation(s)
- Benedetta Leuner
- Department of Psychology, Princeton University, Princeton, New Jersey 08544, USA
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165
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Wiskott L, Rasch MJ, Kempermann G. A functional hypothesis for adult hippocampal neurogenesis: avoidance of catastrophic interference in the dentate gyrus. Hippocampus 2006; 16:329-43. [PMID: 16435309 DOI: 10.1002/hipo.20167] [Citation(s) in RCA: 225] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The dentate gyrus is part of the hippocampal memory system and special in that it generates new neurons throughout life. Here we discuss the question of what the functional role of these new neurons might be. Our hypothesis is that they help the dentate gyrus to avoid the problem of catastrophic interference when adapting to new environments. We assume that old neurons are rather stable and preserve an optimal encoding learned for known environments while new neurons are plastic to adapt to those features that are qualitatively new in a new environment. A simple network simulation demonstrates that adding new plastic neurons is indeed a successful strategy for adaptation without catastrophic interference.
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Affiliation(s)
- Laurenz Wiskott
- Institute for Theoretical Biology, Humboldt-University, Berlin, Germany.
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166
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Lemaire V, Lamarque S, Le Moal M, Piazza PV, Abrous DN. Postnatal stimulation of the pups counteracts prenatal stress-induced deficits in hippocampal neurogenesis. Biol Psychiatry 2006; 59:786-92. [PMID: 16460692 DOI: 10.1016/j.biopsych.2005.11.009] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 09/09/2005] [Accepted: 11/30/2005] [Indexed: 11/22/2022]
Abstract
BACKGROUND Prenatal stress constitutes a developmental risk factor for later psychopathology. The behavioral disorders are sustained by neurobiological alterations including long-term reduction of hippocampal neurogenesis; its deregulation has been involved in cognitive impairments, mood disorders and addiction. A major goal is to define periods in development and strategies for intervening to prevent the effects of early stressful events. We investigated the ability of a postnatal infantile stimulation to prevent prenatal stress-induced alteration in hippocampal neurogenesis. METHODS The influence of postnatal handling on prenatal stress-induced changes in hippocampal neurogenesis was examined in 4 and 26 month-old male rats. Three distinct phases of the neurogenesis were studied: proliferation, survival and neuronal differentiation. RESULTS Prenatal stress reduced hippocampal cell proliferation all throughout life. Furthermore, the survival rate of newborn cells, the number of immature neurons and the number of differentiated new neurons were reduced in young and old prenatally-stressed rats. All those deleterious effects were counteracted by neonatal handling. CONCLUSIONS These data show that finer aspects of brain shaping can be rewired by environmental influences occurring at sensitive phase of development. They also suggest that infantile stimulation may reverse the appearance of behavioral disorders induced by early life stress.
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Affiliation(s)
- Valerie Lemaire
- Institut National de la Santé et de la Recherche Médicale U588, Institut François Magendie, University of Bordeaux II, Bordeaux Cedex, France
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167
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Lledo PM, Alonso M, Grubb MS. Adult neurogenesis and functional plasticity in neuronal circuits. Nat Rev Neurosci 2006; 7:179-93. [PMID: 16495940 DOI: 10.1038/nrn1867] [Citation(s) in RCA: 1017] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The adult brain is a plastic place. To ensure that the mature nervous system's control of behaviour is flexible in the face of a varying environment, morphological and physiological changes are possible at many levels, including that of the entire cell. In two areas of the adult brain - the olfactory bulb and the dentate gyrus - new neurons are generated throughout life and form an integral part of the normal functional circuitry. This process is not fixed, but highly modulated, revealing a plastic mechanism by which the brain's performance can be optimized for a given environment. The functional benefits of this whole-cell plasticity, however, remain a matter for debate.
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Affiliation(s)
- Pierre-Marie Lledo
- Laboratory of Perception and Memory, Institut Pasteur, Centre National de la Recherche Scientifique Unit de Recherche Associée 2182, 25, rue du Docteur Roux, 75724 Paris cedex 15, France.
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168
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Montaron MF, Drapeau E, Dupret D, Kitchener P, Aurousseau C, Le Moal M, Piazza PV, Abrous DN. Lifelong corticosterone level determines age-related decline in neurogenesis and memory. Neurobiol Aging 2006; 27:645-54. [PMID: 15953661 DOI: 10.1016/j.neurobiolaging.2005.02.014] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Revised: 01/04/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022]
Abstract
Ageing is accompanied by an alteration of spatial memory, a decline in hippocampal neurogenesis and a dysregulation of the hypothalamic-pituitary axis (HPA) leading to elevated levels of circulating corticosterone. However, the role of the HPA axis in age-related decline in cognitive functions and in neurogenesis decline remains unclear. We found that suppression of glucocorticoids secretion from midlife to the rest of the animals' life increases neurogenesis in old animals and prevents the emergence of age-related memory disorders. Reciprocally, aged rats with a chronic upregulation of the HPA axis exhibit not only spatial memory impairments but also very low levels of hippocampal cell proliferation and survival. Altogether, these results indicate that the extent of lifetime exposure to glucocorticoids determines the extent of age-related decline in hippocampal neurogenesis and consequently age-related cognitive dysfunctions.
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Affiliation(s)
- M F Montaron
- Laboratoire de Physiopathologie du Comportement, I.N.S.E.R.M. Unité 588, Université de Bordeaux II, Domaine de Carreire, 146, rue Léo. Saignat, 33077 Bordeaux Cedex, France
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169
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Scerri C, Stewart CA, Breen KC, Balfour DJK. The effects of chronic nicotine on spatial learning and bromodeoxyuridine incorporation into the dentate gyrus of the rat. Psychopharmacology (Berl) 2006; 184:540-6. [PMID: 16025316 DOI: 10.1007/s00213-005-0086-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Accepted: 05/27/2005] [Indexed: 01/05/2023]
Abstract
RATIONALE Nicotine is reported to improve learning and memory in experimental animals. Improved learning and memory has also been related to increased neurogenesis in the dentate gyrus (DG) of the hippocampal formation. Surprisingly, recent studies suggest that self-administered nicotine depresses cell proliferation in the DG. OBJECTIVE To test the hypothesis that the effects of nicotine on cell proliferation in the DG and learning and memory depend upon the nicotine dose administered. METHODS Rats were chronically infused from subcutaneous osmotic mini pumps with nicotine (0.25 or 4 mg kg(-1) day(-1)) or the saline vehicle for 10 days. Half the rats in each treatment group were trained to locate a hidden platform in a water maze task on days 4-7; a probe trial was performed on day 8. The remaining rats remained in their home cages. The effects of nicotine and of training in the water maze task on cell genesis in the DG were determined by measuring 5-bromo-2'-deoxyuridine (BrDU) uptake using fluorescence immunohistochemistry. RESULTS Training in the water maze task increased cell proliferation in the DG. Infusions of nicotine at 4 mg kg(-1) day(-1), but not 0.25 mg kg(-1) day(-1), decreased cell proliferation in both untrained animals and animals trained in the maze and impaired spatial learning. CONCLUSIONS The data suggest that learning in the water maze task is impaired by higher doses of nicotine tested, and that this response may be related to reduced cell genesis in the DG.
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Affiliation(s)
- Charles Scerri
- Section of Psychiatry and Behavioural Sciences, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland, DD1 9SY, UK
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170
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Rochefort C, Lledo PM. Short-term survival of newborn neurons in the adult olfactory bulb after exposure to a complex odor environment. Eur J Neurosci 2006; 22:2863-70. [PMID: 16324121 DOI: 10.1111/j.1460-9568.2005.04486.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In the olfactory bulb of adult mice, new neurons are continually integrated into existing neuronal networks. Previous studies have demonstrated that exposure to a complex odor environment increases the incorporation of newborn bulbar neurons without modifying the proliferation rate. Whether this incorporation is transient or leads to the long-lasting presence of new neurons has not yet been answered. Because a transient increase of new neurons impacts olfactory information processing differently than a long-lasting increase, we conducted experiments to investigate the time course of survival and cell death of newly generated bulbar neurons following exposure to an enriched olfactory environment. Dividing cells were labeled with bromodeoxyuridine (BrdU) and were counted at several survival time points thereafter. Interestingly, whereas the number of surviving BrdU-labeled cells was elevated at the time when animals were withdrawn from their enriched housing, this number returned to control level 1 month later. Similarly, when olfactory memory was investigated, we found that the improvement of short-term memory, induced by enriched odor exposure, lasted less than 1 month. These findings indicate not only that the recruitment of newborn neurons closely followed the degree of environment complexity, but also that olfactory memory is tightly associated with the level of ongoing neurogenesis in the adult olfactory bulb.
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Affiliation(s)
- Christelle Rochefort
- Pasteur Institute, Laboratory of Perception and Memory, CNRS UMR 2182, 25 rue du Dr Roux, 75015 Paris, France.
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171
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Mandairon N, Sacquet J, Jourdan F, Didier A. Long-term fate and distribution of newborn cells in the adult mouse olfactory bulb: Influences of olfactory deprivation. Neuroscience 2006; 141:443-51. [PMID: 16713121 DOI: 10.1016/j.neuroscience.2006.03.066] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 03/15/2006] [Accepted: 03/15/2006] [Indexed: 11/24/2022]
Abstract
The adult subventricular zone produces neuroblasts that migrate to the main olfactory bulb, where they differentiate into interneurons in the glomerular and granular layers. Using bromodeoxyuridine labeling, the survival of newborn cells was assessed in these two layers of the MOB in control mice and in mice unilaterally deprived from sensory input by naris occlusion. In control main olfactory bulbs, bromodeoxyuridine-positive cell density decreased about 70% between 15 and 180 days post-bromodeoxyuridine administration but earlier in the glomerular layer than in the granular layer. At all time points examined, newborn cell density was higher in the deep granular layer than in the superficial granular layer. Occlusion started at the age of 2 months and lasted for 15, 30, 45, 60 or 180 days. The newborn cell survival was similarly reduced in both layers by occlusion, during a critical period 15 and 45 days post-occlusion. Interestingly, olfactory deprivation decreased bromodeoxyuridine-positive cell density in the deep granular layer only, indicating a greater dependence of cell fate on sensory input in this sub-layer. Neuronal differentiation was assessed in the granular layer and glomerular layer by multiple double-labeling 45 days post-bromodeoxyuridine-injections, the time point at which the proportion of bromodeoxyuridine-positive cells expressing a neuronal marker reached approximately 85% in the granular layer and approximately 50% in the glomerular layer. Naris occlusion did not significantly affect these proportions. Taken together, our results reveal that the survival of newborn cells has a different time course in the glomerular layer and in the granular layer, but is similarly decreased in each layer by olfactory deprivation. In addition, our data suggest a functional heterogeneity of neurogenesis within the granular layer.
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Affiliation(s)
- N Mandairon
- Laboratoire de Neurosciences et Systèmes Sensoriels, CNRS UMR 5020, Université Claude Bernard Lyon 1, 50 Avenue Tony Garnier, 6936, Lyon Cedex 07, France.
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172
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Smad-dependent alterations of PPT cholinergic neurons as a pathophysiological mechanism of age-related sleep-dependent memory impairments. Neurobiol Aging 2005; 27:1848-58. [PMID: 16316709 DOI: 10.1016/j.neurobiolaging.2005.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 10/07/2005] [Accepted: 10/18/2005] [Indexed: 11/29/2022]
Abstract
In humans, memory impairments are highly prevalent in the aged population, but their functional and structural origins are still unknown. We hypothesized that circadian rhythm alterations may predict spatial memory impairment in aged rats. We demonstrate an association between sleep/wake circadian rhythm disturbances (non-REM sleep fragmentation) and spatial memory impairments in aged rats. We show by light and electron microscopy that these age-related disruptions in circadian rhythm and spatial memory are also associated with degeneration of cholinergic neurons of the pedunculopontine nucleus (PPT), a structure known to be involved in sleep and cognitive functions and which is altered during aging. Finally, we demonstrate that a trophic deregulation of the PPT occur in aged impaired rats, involving an over activation of the TGFbeta-Smad cascade, a signalling pathway involved in neurodegeneration. In conclusion these results provide a new pathophysiological mechanism for age-related sleep-dependent memory impairments opening the ground for the development of new therapeutic approaches of these pathologies.
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173
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Lamont SR, Stanwell BJ, Hill R, Reid IC, Stewart CA. Ketamine pre-treatment dissociates the effects of electroconvulsive stimulation on mossy fibre sprouting and cellular proliferation in the dentate gyrus. Brain Res 2005; 1053:27-32. [PMID: 16045900 DOI: 10.1016/j.brainres.2005.06.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Revised: 06/02/2005] [Accepted: 06/05/2005] [Indexed: 11/16/2022]
Abstract
Electroconvulsive stimulation (ECS), the experimental analogue of electroconvulsive therapy (ECT), has been shown to produce both functional and structural effects in the hippocampal formation in infrahuman species. These changes may relate to the antidepressant and cognitive effects of ECT observed in patients treated for severe depressive disorders. Recent studies have described both enhanced neurogenesis in the dentate gyrus of the hippocampus and sprouting of mossy fibre projections from granule cells. The behavioural significance of these effects remains uncertain. In this study, we examined whether ketamine, a clinically available non-competitive NMDA receptor channel blocker, could block both of these "trophic" effects. Rats were given a course of eight spaced ECS or sham treatments under either halothane or ketamine anaesthesia. The thymidine analogue bromodeoxyuridine was administered to assess the degree of hippocampal cell proliferation and mossy fibre sprouting was quantified using the Timm staining method. Pre-treatment with ketamine dissociated these effects such that mossy fibre sprouting was attenuated significantly, while cell proliferation was unaffected. This dissociation may prove useful in determining the behavioural significance of these hippocampal changes, if any, for either the antidepressant or cognitive consequences of ECT.
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Affiliation(s)
- Steven R Lamont
- University of Dundee, Division of Pathology and Neuroscience, Section of Psychiatry and Behavioural Sciences, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
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174
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Olariu A, Cleaver KM, Shore LE, Brewer MD, Cameron HA. A natural form of learning can increase and decrease the survival of new neurons in the dentate gyrus. Hippocampus 2005; 15:750-62. [PMID: 16010660 DOI: 10.1002/hipo.20097] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Granule cells born in the adult dentate gyrus undergo a 4-week developmental period characterized by high susceptibility to cell death. Two forms of hippocampus-dependent learning have been shown to rescue many of the new neurons during this critical period. Here, we show that a natural form of associative learning, social transmission of food preference (STFP), can either increase or decrease the survival of young granule cells in adult rats. Increased numbers of pyknotic as well as phospho-Akt-expressing BrdU-labeled cells were seen 1 day after STFP training, indicating that training rapidly induces both cell death and active suppression of cell death in different subsets. A single day of training for STFP increased the survival of 8-day-old BrdU-labeled cells when examined 1 week later. In contrast, 2 days of training decreased the survival of BrdU-labeled cells and the density of immature neurons, identified with crmp-4. This change from increased to decreased survival could not be accounted for by the ages of the cells. Instead, we propose that training may initially increase young granule cell survival, then, if continued, cause them to die. This complex regulation of cell death could potentially serve to maintain granule cells that are actively involved in memory consolidation, while rapidly using and discarding young granule cells whose training is complete to make space for new naïve neurons.
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Affiliation(s)
- Ana Olariu
- Unit on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, USA
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175
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Tozuka Y, Fukuda S, Namba T, Seki T, Hisatsune T. GABAergic Excitation Promotes Neuronal Differentiation in Adult Hippocampal Progenitor Cells. Neuron 2005; 47:803-15. [PMID: 16157276 DOI: 10.1016/j.neuron.2005.08.023] [Citation(s) in RCA: 565] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Revised: 07/05/2005] [Accepted: 08/17/2005] [Indexed: 10/25/2022]
Abstract
Hippocampal activity influences neurogenesis in the adult dentate gyrus; however, little is known about the involvement of the hippocampal circuitry in this process. In the subgranular zone of the adult dentate gyrus, neurogenesis involves a series of differentiation steps from radial glia-like stem/progenitor (type-1) cells, to transiently amplifying neuronal progenitor (type-2) cells, to postmitotic neurons. In this study, we conducted GFP-targeted recordings of progenitor cells in fresh hippocampal slices from nestin-GFP mice and found that neuronal progenitor (type-2) cells receive active direct neural inputs from the hippocampal circuitry. This input was GABAergic but not glutamatergic. The GABAergic inputs depolarized type-2 cells because of their elevated [Cl(-)](i). This excitation initiated an increase of [Ca(2+)](i) and the expression of NeuroD. A BrdU-pulse labeling study with GABA(A)-R agonists demonstrated the promotion of neuronal differentiation via this GABAergic excitation. Thus, it appears that GABAergic inputs to hippocampal progenitor cells promote activity-dependent neuronal differentiation.
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Affiliation(s)
- Yusuke Tozuka
- Department of Integrated Biosciences, University of Tokyo, Kashiwa 277-8562, Japan
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176
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Ehninger D, Kempermann G. Paradoxical effects of learning the Morris water maze on adult hippocampal neurogenesis in mice may be explained by a combination of stress and physical activity. GENES BRAIN AND BEHAVIOR 2005; 5:29-39. [PMID: 16436186 DOI: 10.1111/j.1601-183x.2005.00129.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Studies in rats that assessed the relation of hippocampus-dependent learning and adult hippocampal neurogenesis suggested a direct regulatory effect of learning on neurogenesis, whereas a similar study in mice had not found such causal link. We here report a substantial decrease of BrdU-positive cells and other measures of adult hippocampal neurogenesis in mice trained in the hidden (HID) or cued version (VIS) of the Morris water maze as compared to untrained animals (CTR). Particularly, cells on advanced stages of neuronal development contributed to this decrease, whereas earlier progenitors (type 2 cells) were not diminished in HID, but were diminished in VIS as compared to CTR. The differential regulation of type 2 cells in HID and VIS may have been caused by a different degree of physical activity, given that a time-yoked control group did not differ from HID, and type 2 cells reportedly constitute the proliferative dentate gyrus population that primarily responds to physical activity. The decrease of hippocampal neurogenesis by water maze training was reversible by pre-exposing animals to the water maze prior to training, suggesting that stress associated with training may have caused the acute downregulation of adult neurogenesis. We propose that in mice the Morris water maze does not provide a pure enough learning stimulus to study the presumed effects of 'learning' on adult neurogenesis. In addition, however, our data show that physical activity that is intricately linked to many cognitive tasks in rodents might play an important role in explaining effects of learning on cellular hippocampal plasticity.
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Affiliation(s)
- D Ehninger
- Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, and Volkswagenstiftung Research Group, Department of Neurology, Charité University Medicine Berlin, Berlin, Germany
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177
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Mohapel P, Leanza G, Kokaia M, Lindvall O. Forebrain acetylcholine regulates adult hippocampal neurogenesis and learning. Neurobiol Aging 2005; 26:939-46. [PMID: 15718053 DOI: 10.1016/j.neurobiolaging.2004.07.015] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2004] [Revised: 07/19/2004] [Accepted: 07/30/2004] [Indexed: 01/09/2023]
Abstract
Hippocampus-mediated learning enhances neurogenesis in the adult dentate gyrus (DG), and this process has been suggested to be involved in memory formation. The hippocampus receives abundant cholinergic innervation and acetylcholine (ACh) plays an important role in learning and Alzheimer's disease (AD) pathophysiology. Here, we show that a selective neurotoxic lesion of forebrain cholinergic input with 192 IgG-saporin reduces DG neurogenesis with a concurrent impairment in spatial memory. Conversely, systemic administration of the cholinergic agonist physostigmine increases DG neurogenesis. We find that changes of forebrain ACh levels primarily influence the proliferation and/or the short-term survival rather than the long-term survival or differentiation of the new neurons. We further demonstrate that these newly born cells express the muscarinic receptor subtypes M1 and M4. Our data provide evidence that forebrain ACh promotes neurogenesis, and suggest that the impaired cholinergic function in AD may in part contribute to deficits in learning and memory through reductions in the formation of new hippocampal neurons.
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Affiliation(s)
- Paul Mohapel
- Section of Restorative Neurology, Wallenberg Neuroscience Centre, BMC A11, SE-221 84 Lund, Sweden.
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178
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Van der Borght K, Meerlo P, Luiten PGM, Eggen BJL, Van der Zee EA. Effects of active shock avoidance learning on hippocampal neurogenesis and plasma levels of corticosterone. Behav Brain Res 2005; 157:23-30. [PMID: 15617767 DOI: 10.1016/j.bbr.2004.06.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Revised: 06/04/2004] [Accepted: 06/06/2004] [Indexed: 10/26/2022]
Abstract
Hippocampal granule neurons that are newly formed during adulthood might be involved in learning and memory processes. Experimental data suggest that only hippocampus-dependent learning tasks stimulate neurogenesis. To further address this issue, the effects of active shock avoidance (ASA) learning on hippocampal progenitor proliferation and survival of newly formed cells were investigated. ASA training, although considered as hippocampus-independent, is known to induce several neurobiological alterations in the hippocampus. Adult Wistar rats were trained in a shuttle box using a 1-day or 4-day paradigm and brains were analyzed for the mitotic marker Ki-67. Effects on survival of newly generated cells were examined by immunocytochemistry for 5-bromo-2-deoxyuridine (BrdU), which was injected 1 week before the training. Neither proliferation nor survival was affected by the ASA learning task. Because elevated glucocorticoid levels have a negative impact on hippocampal neurogenesis, blood samples were taken throughout the 4-day training paradigm. Both trained animals and control rats that were only placed in the shuttle box without receiving foot shocks showed a similar rise in corticosterone, enabling us to exclusively investigate the effects of ASA learning on neurogenesis without differential interference of stress between groups. On the other hand, the finding that ASA induced elevations in plasma corticosterone, but did not influence proliferation or survival of newly formed cells, indicates that this type of stress does not affect neurogenesis. The present study shows that, in line with the existing data on other hippocampus-independent learning tasks, ASA training has no effect on hippocampal neurogenesis.
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Affiliation(s)
- Karin Van der Borght
- Department of Molecular Neurobiology, Graduate school of Behavioral and Cognitive Neurosciences, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands.
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179
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Abstract
The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.
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Affiliation(s)
- Djoher Nora Abrous
- Laboratoire de Physiopathologie des Comportements, Institut National de la Sané et de la Recherche Médicale, U588, Université de Bordeaux, France.
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180
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Snyder JS, Hong NS, McDonald RJ, Wojtowicz JM. A role for adult neurogenesis in spatial long-term memory. Neuroscience 2005; 130:843-52. [PMID: 15652983 DOI: 10.1016/j.neuroscience.2004.10.009] [Citation(s) in RCA: 638] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2004] [Indexed: 10/26/2022]
Abstract
Adult hippocampal neurogenesis has been linked to learning but details of the relationship between neuronal production and memory formation remain unknown. Using low dose irradiation to inhibit adult hippocampal neurogenesis we show that new neurons aged 4-28 days old at the time of training are required for long-term memory in a spatial version of the water maze. This effect of irradiation was specific since long-term memory for a visibly cued platform remained intact. Furthermore, irradiation just before or after water maze training had no effect on learning or long-term memory. Relationships between learning and new neuron survival, as well as proliferation, were investigated but found non-significant. These results suggest a new role for adult neurogenesis in the formation and/or consolidation of long-term, hippocampus-dependent, spatial memories.
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Affiliation(s)
- J S Snyder
- Department of Physiology, University of Toronto, 1 King's College Circle, Room 3214, Toronto, Ontario, Canada M5S 1A8
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181
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Rao MS, Hattiangady B, Abdel-Rahman A, Stanley DP, Shetty AK. Newly born cells in the ageing dentate gyrus display normal migration, survival and neuronal fate choice but endure retarded early maturation. Eur J Neurosci 2005; 21:464-76. [PMID: 15673445 DOI: 10.1111/j.1460-9568.2005.03853.x] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Addition of new granule cells to the dentate gyrus (DG) from stem or progenitor cells declines considerably during ageing. However, potential age-related alterations in migration, enduring survival and neuronal fate choice of newly born cells, and rate of maturation and dendritic growth of newly differentiated neurons are mostly unknown. We addressed these issues by analysing cells that are positive for 5'-bromodeoxyuridine (BrdU), doublecortin (DCX), BrdU and DCX, and BrdU and neuron-specific nuclear antigen (NeuN) in the DG of young adult, middle-aged and aged F344 rats treated with daily injections of BrdU for 12 consecutive days. Analyses performed at 24 h, 10 days and 5 months after BrdU injections reveal that the extent of new cell production decreases dramatically by middle age but exhibits no change thereafter. Interestingly, fractions of newly formed cells that exhibit appropriate migration and prolonged survival, and fractions of newly born cells that differentiate into neurons, remain stable during ageing. However, in newly formed neurons of the middle-aged and aged DG, the expression of mature neuronal marker NeuN is delayed and early dendritic growth is retarded. Thus, the presence of far fewer new granule cells in the aged DG is not due to alterations in the long term survival and phenotypic differentiation of newly generated cells but solely owing to diminished production of new cells. The results also underscore that the capability of the DG milieu to support neuronal fate choice, migration and enduring survival of newly born cells remains stable even during senescence but its ability to promote rapid neuronal maturation and dendritic growth is diminished as early as middle age.
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Affiliation(s)
- Muddanna S Rao
- Division of Neurosurgery, DUMC Box 3807, Duke University Medical Center, Durham, NC 27710, USA
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182
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Van der Borght K, Wallinga AE, Luiten PGM, Eggen BJL, Van der Zee EA. Morris Water Maze Learning in Two Rat Strains Increases the Expression of the Polysialylated Form of the Neural Cell Adhesion Molecule in the Dentate Gyrus But Has No Effect on Hippocampal Neurogenesis. Behav Neurosci 2005; 119:926-32. [PMID: 16187820 DOI: 10.1037/0735-7044.119.4.926] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the current study, the authors investigated whether Morris water maze learning induces alterations in hippocampal neurogenesis or neural cell adhesion molecule (NCAM) polysialylation in the dentate gyrus. Two frequently used rat strains, Wistar and Sprague-Dawley, were trained in the spatial or the nonspatial version of the water maze. Both training paradigms did not have an effect on survival of newly formed cells that were labeled 7-9 days prior to the training or on progenitor proliferation in the subgranular zone. However, the granule cell layer of the spatially trained rats contained significantly more positive cells of the polysialylated form of the NCAM. These data demonstrate that Morris water maze learning causes plastic change in the dentate gyrus without affecting hippocampal neurogenesis.
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Affiliation(s)
- Karin Van der Borght
- Department of Molecular Neurobiology, Graduate School of Behavioral and Cognitive Neurosciences, University of Groningen, Groningen, The Netherlands.
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183
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Kluska MM, Witte OW, Bolz J, Redecker C. Neurogenesis in the adult dentate gyrus after cortical infarcts: Effects of infarct location, N-methyl-d-aspartate receptor blockade and anti-inflammatory treatment. Neuroscience 2005; 135:723-35. [PMID: 16154293 DOI: 10.1016/j.neuroscience.2005.06.082] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 06/20/2005] [Accepted: 06/22/2005] [Indexed: 01/23/2023]
Abstract
Stimulation of cell proliferation and neurogenesis in the adult dentate gyrus has been observed after focal and global brain ischemia but only little is known about the underlying mechanisms. We here analyzed neurogenesis in the dentate gyrus after small cortical infarcts leaving the hippocampal formation and subcortical regions intact. Using the photothrombosis model in adult rats, focal ischemic infarcts were induced in different cortical areas (sensorimotor forelimb and hindlimb cortex) and proliferating cells were labeled at days 3-14 after infarct induction with bromodeoxyuridine. At 2, 4, and 10 weeks after ischemia, immunocytochemistry was performed with immature neuronal (doublecortin), mature neuronal (neuronal nuclei antigen) and glial (calcium-binding protein beta S100beta) markers. When compared with sham-operated controls, animals with infarcts in the forelimb as well as hindlimb cortex revealed an increase in survival of newborn progenitor cells at four and 10 weeks after the insult with predominance at the ipsilateral side. Triple immunofluorescence and confocal laser scanning microscopy revealed an increase in neurogenesis in all groups that was more pronounced 10 weeks after the infarct. Application of the N-methyl-D-aspartate (NMDA)-receptor antagonist MK-801 during lesion induction significantly enhanced neurogenesis in the dentate gyrus. An even stronger increase in newborn neurons was observed after anti-inflammatory treatment with indomethacine during the first 16 days of the experiment. The present study demonstrates that small cortical infarcts leaving subcortical structures intact increase neurogenesis in the dentate gyrus and that these processes can be stimulated by N-methyl-D-aspartate receptor blockade and anti-inflammatory treatment.
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Affiliation(s)
- M M Kluska
- Department of Neurology, Friedrich-Schiller-University, Erlanger Allee 101, D-07747 Jena, Germany
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184
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Leuner B, Mendolia-Loffredo S, Kozorovitskiy Y, Samburg D, Gould E, Shors TJ. Learning enhances the survival of new neurons beyond the time when the hippocampus is required for memory. J Neurosci 2004; 24:7477-81. [PMID: 15329394 PMCID: PMC3279157 DOI: 10.1523/jneurosci.0204-04.2004] [Citation(s) in RCA: 220] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 05/31/2004] [Accepted: 07/01/2004] [Indexed: 12/16/2022] Open
Abstract
Trace memories are formed when a stimulus event becomes associated with another event that occurs later in time and is discontinuous with the first event. The formation of trace memories enhances the survival of newly generated neurons in the dentate gyrus of the adult hippocampus (Gould et al., 1999a). Here we tested whether the acquisition of trace memories early during training is sufficient to enhance cell survival. We also examined whether the new neurons affected by trace memory formation persist indefinitely or only as long as the hippocampus is necessary for the expression of those memories. Groups of adult rats were injected with bromodeoxyuridine (BrdU), a marker of dividing cells, and trained 1 week later with paired stimuli using a trace eyeblink conditioning task or exposed to the same number of unpaired stimuli. Cell survival was assessed after different numbers of training trials and survival periods after training. Overall cell survival was not enhanced by exposure to 200 trials of paired stimuli during trace conditioning. However, there was a positive correlation between performance of individual animals and cell survival. In addition, exposure to 800 trials of paired stimuli during trace conditioning increased the number of BrdU-labeled cells 60 d after training. The vast majority of these cells were neurons and coexpressed the neuronal markers class IIIbeta-tubulin or neuronal nuclei. These data suggest that individual differences in associative learning predict whether new neurons will survive and that once affected, these neurons remain for months and beyond the time when they are required for the retention of trace memories.
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Affiliation(s)
- Bendetta Leuner
- Department of Psychology and Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854, USA
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185
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Reif A, Schmitt A, Fritzen S, Chourbaji S, Bartsch C, Urani A, Wycislo M, Mössner R, Sommer C, Gass P, Lesch KP. Differential effect of endothelial nitric oxide synthase (NOS-III) on the regulation of adult neurogenesis and behaviour. Eur J Neurosci 2004; 20:885-95. [PMID: 15305857 DOI: 10.1111/j.1460-9568.2004.03559.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Although it has been postulated that adult neurogenesis, i.e. the generation of functional neurons from progenitor cells in the mammalian brain, is involved in both the pathogenesis of depressive disorders and the therapeutic effect of antidepressant drugs, its regulation is still poorly understood. Nitric oxide, a gaseous messenger molecule, represents a possible modulating agent as it is involved in learning and memory formation as well as synapto- and morphogenesis. Here we investigated whether adult neurogenesis is altered in mice lacking endothelial nitric oxide synthase (NOS-III). Compared to wild-type littermates, NOS-III-deficient mice showed a significant reduction in neuronal progenitor cell proliferation in the dentate gyrus, suggesting a role for NOS-III in the stimulation of neuroneogenesis. NeuN, beta-III-tubulin and GFAP double-immunolabelling demonstrated that proliferating progenitor cells differentiate preferentially into neurons but not into astrocytes. However, when the survival rate of newly formed cells was examined no difference between wild-type and NOS-III knockout mice was found, suggesting that NOS-III selectively exerts its effects on the proliferation of progenitor cells. This might be mediated by a decrease in vascular endothelial growth factor (VEGF) transcripts in the hippocampus of knockout animals. At the behavioural level, while NOS-III knockout mice displayed better and faster learning in a learned helplessness paradigm, no depression-like behaviours were observed. In conclusion, our results indicated that NOS-III is involved in the proliferation of neuronal progenitor cells, although behavioural analysis does not provide evidence for a pro-depressive effect of reduced neuroneogenesis.
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Affiliation(s)
- Andreas Reif
- Molecular and Clinical Psychobiology, Department of Psychiatry and Psychotherapy, Julius-Maximilians-University Würzburg, Füchsleinstr. 15, D-97080 Würzburg, Germany.
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186
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Mirescu C, Peters JD, Gould E. Early life experience alters response of adult neurogenesis to stress. Nat Neurosci 2004; 7:841-6. [PMID: 15273691 DOI: 10.1038/nn1290] [Citation(s) in RCA: 442] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Accepted: 06/15/2004] [Indexed: 11/09/2022]
Abstract
Maternal deprivation produces persistent abnormalities in behavioral and neuroendocrine functions associated with the hippocampus, a brain region that shows considerable structural change in response to experience throughout life. Here we show that adverse experience early in life affects the regulation of adult neurogenesis in the hippocampus. More specifically, a decrease in cell proliferation and immature neuron production are observed in the dentate gyrus of adult rats that are maternally separated as pups. Although maternally separated rats show normal basal levels of corticosterone, the suppression of cell proliferation in these rats can be reversed by lowering corticosterone below the control value. In addition, normal stress-induced suppression of cell proliferation and neurogenesis, despite normal activation of the hypothalamic pituitary adrenal (HPA) axis, is not observed in maternally separated rats. Our results suggest that early adverse experience inhibits structural plasticity via hypersensitivity to glucocorticoids and diminishes the ability of the hippocampus to respond to stress in adulthood.
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Affiliation(s)
- Christian Mirescu
- Department of Psychology, Princeton University, Princeton, New Jersey 08544, USA
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187
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Montaron MF, Koehl M, Lemaire V, Drapeau E, Abrous DN, Le Moal M. Environmentally induced long-term structural changes: cues for functional orientation and vulnerabilities. Neurotox Res 2004; 6:571-80. [PMID: 15639789 DOI: 10.1007/bf03033453] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Environmental challenges profoundly modify phenotypes and disrupt inherent developmental programs both at functional and structural levels. As an example, we have studied the impact of these environmental influences on adult neurogenesis in the dentate gyrus. Neurogenesis results from an inherent program, participates to hippocampal network organization and, as a consequence, to the various functional abilities depending on this region, including memories. In preclinical studies of aging we have shown that phenotypes vulnerable to the development of spatial memory disorders are characterized by lower hippocampal neurogenesis. We have hypothesized that these interindividual variations in functional expression of neurogenesis in senescent subjects could be predicted early in life. Indeed, a behavioral response (novelty-induced locomotor reactivity) and a biological trait (hypothalamo-pituitary-adrenal axis activity), which are predictive of cognitive impairments later in life, are related to neurogenesis in young adult rats. This suggests that subjects starting off with an impaired neurogenesis, here rats that are high reactive to stress, are predisposed for the development of age-related cognitive disorders. We have further shown that these inter-individual differences result from early deleterious life events. Indeed, prenatal stress orients neurogenesis in pathological ways for the entire life, and precipitates age-related cognitive impairments. Altogether these data suggest first that hippocampal neurogenesis plays a pivotal role in environmentally-induced vulnerability to the development of pathological aging, and second that environmental challenges and life events orient structural developments, leading to different phenotypes.
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Affiliation(s)
- M F Montaron
- INSERM U588, Domaine de Carreire, Rue Camille Saint Saëns, University of Bordeaux II Bordeaux Cedex 33077, France
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188
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Shors TJ, Townsend DA, Zhao M, Kozorovitskiy Y, Gould E. Neurogenesis may relate to some but not all types of hippocampal-dependent learning. Hippocampus 2002; 12:578-84. [PMID: 12440573 PMCID: PMC3289536 DOI: 10.1002/hipo.10103] [Citation(s) in RCA: 641] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The hippocampal formation generates new neurons throughout adulthood. Recent studies indicate that these cells possess the morphology and physiological properties of more established neurons. However, the function of adult generated neurons is still a matter of debate. We previously demonstrated that certain forms of associative learning can enhance the survival of new neurons and a reduction in neurogenesis coincides with impaired learning of the hippocampal-dependent task of trace eyeblink conditioning. Using the toxin methylazoxymethanol acetate (MAM) for proliferating cells, we tested whether reduction of neurogenesis affected learning and performance associated with different hippocampal dependent tasks: spatial navigation learning in a Morris water maze, fear responses to context and an explicit cue after training with a trace fear paradigm. We also examined exploratory behavior in an elevated plus maze. Rats were injected with MAM (7 mg/kg) or saline for 14 days, concurrent with BrdU, to label new neurons on days 10, 12, and 14. After treatment, groups of rats were tested in the various tasks. A significant reduction in new neurons in the adult hippocampus was associated with impaired performance in some tasks, but not with others. Specifically, treatment with the antimitotic agent reduced the amount of fear acquired after exposure to a trace fear conditioning paradigm but did not affect contextual fear conditioning or spatial navigation learning in the Morris water maze. Nor did MAM treatment affect exploration in the elevated plus maze. These results combined with previous ones suggest that neurogenesis may be associated with the formation of some but not all types of hippocampal-dependent memories.
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Affiliation(s)
- Tracey J Shors
- Department of Psychology and Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854-8020, USA.
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