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Hattiangady B, Shetty AK. Implications of decreased hippocampal neurogenesis in chronic temporal lobe epilepsy. Epilepsia 2008; 49 Suppl 5:26-41. [PMID: 18522598 DOI: 10.1111/j.1528-1167.2008.01635.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Temporal lobe epilepsy (TLE), characterized by spontaneous recurrent motor seizures (SRMS), learning and memory impairments, and depression, is associated with neurodegeneration, abnormal reorganization of the circuitry, and loss of functional inhibition in the hippocampal and extrahippocampal regions. Over the last decade, abnormal neurogenesis in the dentate gyrus (DG) has emerged as another hallmark of TLE. Increased DG neurogenesis and recruitment of newly born neurons into the epileptogenic hippocampal circuitry is a characteristic phenomenon occurring during the early phase after the initial precipitating injury such as status epilepticus. However, the chronic phase of the disease displays substantially declined DG neurogenesis, which is associated with SRMS, learning and memory impairments, and depression. This review focuses on DG neurogenesis in the chronic phase of TLE and first confers the extent and mechanisms of declined DG neurogenesis in chronic TLE. The available data on production, survival and neuronal fate choice decision of newly born cells, stability of hippocampal stem cell numbers, and changes in the hippocampal microenvironment in chronic TLE are considered. The next section discusses the possible contribution of declined DG neurogenesis to the pathophysiology of chronic TLE, which includes its potential effects on spontaneous recurrent seizures, cognitive dysfunction, and depression. The subsequent section considers strategies that may be useful for augmenting DG neurogenesis in chronic TLE, which encompass stem cell grafting, administration of distinct neurotrophic factors, physical exercise, exposure to enriched environment, and antidepressant therapy. The final section suggests possible ramifications of increasing the DG neurogenesis in chronic epilepsy.
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Affiliation(s)
- Bharathi Hattiangady
- Division of Neurosurgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
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152
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Tapia-Arancibia L, Aliaga E, Silhol M, Arancibia S. New insights into brain BDNF function in normal aging and Alzheimer disease. ACTA ACUST UNITED AC 2008; 59:201-20. [PMID: 18708092 DOI: 10.1016/j.brainresrev.2008.07.007] [Citation(s) in RCA: 420] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 07/30/2008] [Accepted: 07/30/2008] [Indexed: 01/13/2023]
Abstract
The decline observed during aging involves multiple factors that influence several systems. It is the case for learning and memory processes which are severely reduced with aging. It is admitted that these cognitive effects result from impaired neuronal plasticity, which is altered in normal aging but mainly in Alzheimer disease. Neurotrophins and their receptors, notably BDNF, are expressed in brain areas exhibiting a high degree of plasticity (i.e. the hippocampus, cerebral cortex) and are considered as genuine molecular mediators of functional and morphological synaptic plasticity. Modification of BDNF and/or the expression of its receptors (TrkB.FL, TrkB.T1 and TrkB.T2) have been described during normal aging and Alzheimer disease. Interestingly, recent findings show that some physiologic or pathologic age-associated changes in the central nervous system could be offset by administration of exogenous BDNF and/or by stimulating its receptor expression. These molecules may thus represent a physiological reserve which could determine physiological or pathological aging. These data suggest that boosting the expression or activity of these endogenous protective systems may be a promising therapeutic alternative to enhance healthy aging.
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153
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Perera TD, Park S, Nemirovskaya Y. Cognitive role of neurogenesis in depression and antidepressant treatment. Neuroscientist 2008; 14:326-38. [PMID: 18612087 DOI: 10.1177/1073858408317242] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The discovery of newborn neurons in the adult brain has generated enormous interest over the past decade. Although this process is well documented in the hippocampus and olfactory bulb, the possibility of neuron formation in other brain regions is under vigorous debate. Neurogenesis within the adult hippocampus is suppressed by factors that predispose to major depression and stimulated by antidepressant interventions. This pattern has generated the hypothesis that impaired neurogenesis is pathoetiological in depression and stimulation of newborn neurons essential for effective antidepressant action. This review critically evaluates the evidence in support of and in conflict with this theory. The literature is divided into three areas: neuronal maturation, factors that influence neurogenesis rates, and function of newborn neurons. Unique elements in each of these areas allow for the refinement of the hypothesis. Newborn hippocampal neurons appear to be necessary for detecting subtle environmental changes and coupling emotions to external context. Thus speculatively, stress-induced suppression of neurogenesis would uncouple emotions from external context leading to a negative mood state. Persistence of negative mood beyond the duration of the initial stressor can be defined as major depression. Antidepressant-induced neurogenesis therefore would restore coupling of mood with environment, leading to the resolution of depression. This conceptual framework is provisional and merits evaluation in further experimentation. Critically, manipulation of newborn hippocampal neurons may offer a portal of entry for more effective antidepressant treatment strategies.
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Affiliation(s)
- Tarique D Perera
- Department of Psychiatry, College of Physicians and Surgeons, Columbia University Medical Center, and the New York State Psychiatric Institute, New York, New York 10032, USA.
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154
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Hayakawa N, Abe M, Eto R, Kato H, Araki T. Age-related changes of NGF, BDNF, parvalbumin and neuronal nitric oxide synthase immunoreactivity in the mouse hippocampal CA1 sector. Metab Brain Dis 2008; 23:199-211. [PMID: 18421425 DOI: 10.1007/s11011-008-9084-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Accepted: 03/06/2008] [Indexed: 01/19/2023]
Abstract
We investigated the age-related alterations in nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), parvalbumin and neuronal nitric oxide synthase (nNOS) immunoreactivity of the mouse hippocampal CA1 sector. NGF and BDNF immunoreactivity was unchanged in the hippocampal CA1 pyramidal neurons from 2 to 50-59 weeks of birth. In contrast, a significant increase in the NGF and BDNF immunoreactivity was observed in glial cells of the hippocampal CA1 sector from 40-42 to 50-59 weeks of birth. On the other hand, the number of parvalbumin- and nNOS-positive interneurons was unchanged in the hippocampal CA1 sector during aging processes, except for a significant decrease of nNOS-positive interneurons 2 weeks of birth. Our results indicate that NGF and BDNF immunoreactivity was unaltered in the hippocampal CA1 pyramidal neurons during aging processes. In contrast, a significant increase in the NGF and BDNF immunoreactivity was observed in glial cells of the hippocampal CA1 sector during aging processes. The present study also shows that the number of parvalbumin- and nNOS-positive interneurons was unchanged in the hippocampal CA1 sector during aging processes, except for a significant decrease of nNOS-positive interneurons 2 weeks of birth. These results demonstrate that the expression of glial NGF and BDNF may play a key role for helping survival and maintenance of pyramidal neurons and neuronal functions in the hippocampal CA1 sector during aging processes. Furthermore, our findings suggest that parvalbumin- and nNOS-positive interneurons in the hippocampal CA1 sector are resistant to aging processes. Moreover, our findings suggest that nitric oxide synthesized by the nNOS may play some role for neuronal growth during postnatal development.
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Affiliation(s)
- Natsumi Hayakawa
- Department of Neurobiology and Therapeutics, Graduate School and Faculty of Pharmaceutical Sciences, The University of Tokushima, 1-78, Sho-machi, Tokushima, 770-8505, Japan
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155
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Costa M, Botton P, Mioranzza S, Souza D, Porciúncula L. Caffeine prevents age-associated recognition memory decline and changes brain-derived neurotrophic factor and tirosine kinase receptor (TrkB) content in mice. Neuroscience 2008; 153:1071-8. [DOI: 10.1016/j.neuroscience.2008.03.038] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 03/11/2008] [Accepted: 03/13/2008] [Indexed: 01/28/2023]
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156
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Hattiangady B, Rao MS, Shetty AK. Grafting of striatal precursor cells into hippocampus shortly after status epilepticus restrains chronic temporal lobe epilepsy. Exp Neurol 2008; 212:468-81. [PMID: 18579133 DOI: 10.1016/j.expneurol.2008.04.040] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 04/17/2008] [Accepted: 04/25/2008] [Indexed: 01/05/2023]
Abstract
Status epilepticus (SE) typically progresses into temporal lobe epilepsy (TLE) typified by complex partial seizures. Because sizable fraction of patients with TLE exhibit chronic seizures that are resistant to antiepileptic drugs, alternative therapies that are efficient for diminishing SE-induced chronic epilepsy have great significance. We hypothesize that bilateral grafting of appropriately treated striatal precursor cells into hippocampi shortly after SE is efficacious for diminishing SE-induced chronic epilepsy through long-term survival and differentiation into GABA-ergic neurons. We induced SE in adult rats via graded intraperitoneal injections of kainic acid, bilaterally placed grafts of striatal precursors (pre-treated with fibroblast growth factor-2 and caspase inhibitor) into hippocampi at 4 days post-SE, and examined long-term effects of grafting on spontaneous recurrent motor seizures (SRMS). Analyses at 9-12 months post-grafting revealed that, the overall frequency of SRMS was 67-89% less than that observed in SE-rats that underwent sham-grafting surgery and epilepsy-only controls. Graft cell survival was approximately 33% of injected cells and approximately 69% of surviving cells differentiated into GABA-ergic neurons, which comprised subclasses expressing calbindin, parvalbumin, calretinin and neuropeptide Y. Grafting considerably preserved hippocampal calbindin but had no effects on aberrant mossy fiber sprouting. The results provide novel evidence that bilateral grafting of appropriately treated striatal precursor cells into hippocampi shortly after SE is proficient for greatly reducing the frequency of SRMS on a long-term basis in the chronic epilepsy period. Presence of a large number of GABA-ergic neurons in grafts further suggests that strengthening of the inhibitory control in host hippocampi likely underlies the beneficial effects mediated by grafts.
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Affiliation(s)
- Bharathi Hattiangady
- Department of Surgery (Neurosurgery) Duke University Medical Center, Durham, NC 27710, USA
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157
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Wang JM, Irwin RW, Liu L, Chen S, Brinton RD. Regeneration in a degenerating brain: potential of allopregnanolone as a neuroregenerative agent. Curr Alzheimer Res 2008; 4:510-7. [PMID: 18220513 PMCID: PMC3182411 DOI: 10.2174/156720507783018262] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Confronting the efficacy of a regenerative therapeutic is the degenerative environment that is characterized by neuronal loss, physical plague and glial scar barriers and inflammation. But perhaps more fundamental from a regenerative perspective, are changes in the biochemical milieu of steroid and peptide growth factors, cytokines and neurotransmitter systems. Data from multiple levels of analysis indicate that gonadal steroid hormones and their metabolites can promote neural health whereas their decline or absence are associated with decline in neural health and increased risk of neurodegenerative disease including Alzheimer’s. Among the steroids in decline, is allopregnanolone (APα), a neurosteroid metabolite of progesterone, which was found to be reduced in the serum [1,2] and plasma [3] and brain of aged vs. young subjects [4]. Further, Alzheimer disease (AD) victims showed an even further reduction in plasma and brain levels of APα relative to age-matched neurologically normal controls [1,4,5]. Our earlier work has shown that APα is a neurogenic agent for rodent hippocampal neural progenitors and for human neural progenitor cells derived from the cerebral cortex [6]. Our ongoing research seeks to determine the neurogenic potential of APα in the triple transgenic mouse model of Alzheimer’s disease (3xTgAD) as AD related pathology progresses from imperceptible to mild to severe. Initial analyses suggest that neurogenic potential changes with age in nontransgenic mice and that the neurogenic profile differs between non-transgenic and 3xTgAD mice. Comparative analyses indicate that APα modifies neurogenesis in both non-transgenic and 3xTgAD mice. Preliminary data suggest that APα may modify Alzheimer’s pathology progression. Together the data indicate that APα may maintain the regenerative ability of the brain and modify progression of AD related pathology. Challenges for efficacy of regenerative agents within a degenerative milieu are discussed.
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Affiliation(s)
- Jun Ming Wang
- Department of Pharmacology and Pharmaceutical Sciences and Program in Neuroscience, University of Southern California, School of Pharmacy, 1985 Zonal Avenue, Los Angeles, CA 90089, USA
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158
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Wang JM, Liu L, Irwin RW, Chen S, Brinton RD. Regenerative potential of allopregnanolone. ACTA ACUST UNITED AC 2008; 57:398-409. [DOI: 10.1016/j.brainresrev.2007.08.010] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2007] [Revised: 08/16/2007] [Accepted: 08/25/2007] [Indexed: 01/17/2023]
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159
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Hattiangady B, Rao MS, Shetty AK. Plasticity of hippocampal stem/progenitor cells to enhance neurogenesis in response to kainate-induced injury is lost by middle age. Aging Cell 2008; 7:207-24. [PMID: 18241325 DOI: 10.1111/j.1474-9726.2007.00363.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A remarkable up-regulation of neurogenesis through increased proliferation of neural stem/progenitor cells (NSCs) is a well-known plasticity displayed by the young dentate gyrus (DG) following brain injury. To ascertain whether this plasticity is preserved during aging, we quantified DG neurogenesis in the young adult, middle-aged and aged F344 rats after kainic acid induced hippocampal injury. Measurement of new cells that are added to the dentate granule cell layer (GCL) between post-injury days 4 and 15 using 5'-bromodeoxyuridine labeling revealed an increased addition of new cells in the young DG but not in the middle-aged and aged DG. Quantification of newly born neurons using doublecortin immunostaining also demonstrated a similar trend. Furthermore, the extent of ectopic migration of new neurons into the dentate hilus was dramatically increased in the young DG but was unaltered in the middle-aged and aged DG. However, there was no change in neuronal fate-choice decision of newly born cells following injury in all age groups. Similarly, comparable fractions of new cells that are added to the GCL after injury exhibited 5-month survival and expressed the mature neuronal marker NeuN, regardless of age or injury at the time of their birth. Thus, hippocampal injury does not adequately stimulate NSCs in the middle-aged and aged DG, resulting in no changes in neurogenesis after injury. Interestingly, rates of both neuronal fate-choice decision and long-term survival of newly born cells remain stable with injury in all age groups. These results underscore that the ability of the DG to increase neurogenesis after injury is lost as early as middle age.
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160
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Martin MG, Perga S, Trovò L, Rasola A, Holm P, Rantamäki T, Harkany T, Castrén E, Chiara F, Dotti CG. Cholesterol loss enhances TrkB signaling in hippocampal neurons aging in vitro. Mol Biol Cell 2008; 19:2101-12. [PMID: 18287532 DOI: 10.1091/mbc.e07-09-0897] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Binding of the neurotrophin brain-derived neurotrophic factor (BDNF) to the TrkB receptor is a major survival mechanism during embryonic development. In the aged brain, however, BDNF levels are low, suggesting that if TrkB is to play a role in survival at this stage additional mechanisms must have developed. We here show that TrkB activity is most robust in the hippocampus of 21-d-old BDNF-knockout mice as well as in old, wild-type, and BDNF heterozygous animals. Moreover, robust TrkB activity is evident in old but not young hippocampal neurons differentiating in vitro in the absence of any exogenous neurotrophin and also in neurons from BDNF -/- embryos. Age-associated increase in TrkB activity correlated with a mild yet progressive loss of cholesterol. This, in turn, correlated with increased expression of the cholesterol catabolic enzyme cholesterol 24-hydroxylase. Direct cause-effect, cholesterol loss-high TrkB activity was demonstrated by pharmacological means and by manipulating the levels of cholesterol 24-hydroxylase. Because reduced levels of cholesterol and increased expression of choleseterol-24-hydroxylase were also observed in the hippocampus of aged mice, changes in cellular cholesterol content may be used to modulate receptor activity strength in vivo, autonomously or as a way to complement the natural decay of neurotrophin production.
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Affiliation(s)
- Mauricio G Martin
- VIB and Department of Human Genetics, Catholic University of Leuven, B-3000 Leuven, Belgium
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161
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Swanson KS, Vester BM, Apanavicius CJ, Kirby NA, Schook LB. Implications of age and diet on canine cerebral cortex transcription. Neurobiol Aging 2008; 30:1314-26. [PMID: 18079023 DOI: 10.1016/j.neurobiolaging.2007.10.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 10/18/2007] [Accepted: 10/27/2007] [Indexed: 01/22/2023]
Abstract
Mechanisms contributing to age-related cognitive decline are poorly defined. Thus, we used canine microarrays to compare gene expression profiles of brain tissue from geriatric and young adult dogs. Cerebral cortex samples were collected from six geriatric (12-year old) and six young adult (1-year old) female beagles after being fed one of two diets (animal protein-based versus plant-protein based) for 12 months. RNA samples were hybridized to Affymetrix GeneChip Canine Genome Arrays. Statistical analyses indicated that the age had the greatest impact on gene expression, with 963 transcripts differentially expressed in geriatric dogs. Although not as robust as age, diet affected mRNA abundance of 140 transcripts. As demonstrated in aged rodents and humans, geriatric dogs had increased expression of genes associated with inflammation, stress response, and calcium homeostasis and decreased expression of genes associated with neuropeptide signaling and synaptic transmission. In addition to its existing strengths, availability of gene sequence information and commercial microarrays make the canine a powerful model for studying the effects of aging on cognitive function.
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Affiliation(s)
- Kelly S Swanson
- Department of Animal Sciences, University of Illinois, 162 Animal Sciences Laboratory, Urbana, IL 61801, USA.
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162
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Bachstetter AD, Pabon MM, Cole MJ, Hudson CE, Sanberg PR, Willing AE, Bickford PC, Gemma C. Peripheral injection of human umbilical cord blood stimulates neurogenesis in the aged rat brain. BMC Neurosci 2008; 9:22. [PMID: 18275610 PMCID: PMC2268935 DOI: 10.1186/1471-2202-9-22] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 02/14/2008] [Indexed: 11/12/2022] Open
Abstract
Background Neurogenesis continues to occur throughout life but dramatically decreases with increasing age. This decrease is mostly related to a decline in proliferative activity as a result of an impoverishment of the microenvironment of the aged brain, including a reduction in trophic factors and increased inflammation. Results We determined that human umbilical cord blood mononuclear cells (UCBMC) given peripherally, by an intravenous injection, could rejuvenate the proliferative activity of the aged neural stem/progenitor cells. This increase in proliferation lasted for at least 15 days after the delivery of the UCBMC. Along with the increase in proliferation following UCBMC treatment, an increase in neurogenesis was also found in the aged animals. The increase in neurogenesis as a result of UCBMC treatment seemed to be due to a decrease in inflammation, as a decrease in the number of activated microglia was found and this decrease correlated with the increase in neurogenesis. Conclusion The results demonstrate that a single intravenous injection of UCBMC in aged rats can significantly improve the microenvironment of the aged hippocampus and rejuvenate the aged neural stem/progenitor cells. Our results raise the possibility of a peripherally administered cell therapy as an effective approach to improve the microenvironment of the aged brain.
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Affiliation(s)
- Adam D Bachstetter
- Department of Molecular Pharmacology and Physiology, University of South Florida, College of Medicine, Tampa, FL 33612, USA.
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163
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Ludlow CL, Hoit J, Kent R, Ramig LO, Shrivastav R, Strand E, Yorkston K, Sapienza CM. Translating principles of neural plasticity into research on speech motor control recovery and rehabilitation. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2008; 51:S240-58. [PMID: 18230849 PMCID: PMC2364711 DOI: 10.1044/1092-4388(2008/019)] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
PURPOSE To review the principles of neural plasticity and make recommendations for research on the neural bases for rehabilitation of neurogenic speech disorders. METHOD A working group in speech motor control and disorders developed this report, which examines the potential relevance of basic research on the brain mechanisms involved in neural plasticity and discusses possible similarities and differences for application to speech motor control disorders. The possible involvement of neural plasticity in changes in speech production in normalcy, development, aging, and neurological diseases and disorders was considered. This report focuses on the appropriate use of functional and structural neuroimaging and the design of feasibility studies aimed at understanding how brain mechanisms are altered by environmental manipulations such as training and stimulation and how these changes might enhance the future development of rehabilitative methods for persons with speech motor control disorders. CONCLUSIONS Increased collaboration with neuroscientists working in clinical research centers addressing human communication disorders might foster research in this area. It is hoped that this article will encourage future research on speech motor control disorders to address the principles of neural plasticity and their application for rehabilitation.
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Affiliation(s)
- Christy L Ludlow
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
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164
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Dhanushkodi A, Shetty AK. Is exposure to enriched environment beneficial for functional post-lesional recovery in temporal lobe epilepsy? Neurosci Biobehav Rev 2007; 32:657-74. [PMID: 18178250 DOI: 10.1016/j.neubiorev.2007.10.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 09/24/2007] [Accepted: 10/29/2007] [Indexed: 01/19/2023]
Abstract
Exposure to enriched environment has been shown to induce robust neuronal plasticity in both intact and injured adult central nervous system, including up-regulation of multiple neurotrophic factors, enhanced neurogenesis in the dentate gyrus of the hippocampus, and improved spatial learning and memory function. Neuronal plasticity, though mostly adaptive and abnormal, also occurs during certain neurodegenerative conditions such as the temporal lobe epilepsy (TLE). The TLE is characterized by hippocampal neurodegeneration, aberrant mossy fiber sprouting, spontaneous recurrent motor seizures, cognitive deficits, and abnormally enhanced neurogenesis during the early phase and dramatically declined neurogenesis during the chronic phase of the disease. As environmental enrichment has been found to be beneficial for treating animal models of Alzheimer's, Parkinson's, and Huntington's diseases, there is considerable interest in determining the efficacy of this strategy for preventing or treating chronic TLE after the initial precipitating brain injury. This review first discusses the proof of principle behind the potential application of the environmental enrichment strategy for preventing or treating TLE after brain injury. The subsequent chapters confer the portrayed beneficial effects of enrichment for functional post-lesional recovery in TLE and the possible complications which may arise from housing epilepsy-prone or epileptic rats in enriched environmental conditions. The final segment discusses studies that are essential for further understanding the efficacy of this approach for preventing or treating TLE.
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Affiliation(s)
- Anandh Dhanushkodi
- Medical Research and Surgery Services, Veterans Affairs Medical Center, Durham, NC 27705, USA
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165
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Diminished adult neurogenesis in the marmoset brain precedes old age. Proc Natl Acad Sci U S A 2007; 104:17169-73. [PMID: 17940008 DOI: 10.1073/pnas.0708228104] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
With aging there is a decline in the number of newly generated neurons in the dentate gyrus of the hippocampus. In rodents and tree shrews, this age-related decrease in neurogenesis is evident long before the animals become aged. No previous studies have investigated whether primates exhibit a similar decline in hippocampal neurogenesis with aging. To investigate this possibility, young to middle aged adult common marmosets (Callithrix jacchus) were injected with BrdU and perfused 3 weeks later. The number of newly generated cells in the subgranular zone/granule cell layer of the dentate gyrus was significantly lower in older animals and decreased linearly with age. A similar age-related decline in new cells was observed in the subventricular zone but not in the hilar region of the dentate gyrus. These data demonstrate that a substantial decrease in neurogenesis occurs before the onset of old age in the adult marmoset brain, suggesting the possibility that similar alterations occur in the human brain.
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166
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Rai KS, Hattiangady B, Shetty AK. Enhanced production and dendritic growth of new dentate granule cells in the middle-aged hippocampus following intracerebroventricular FGF-2 infusions. Eur J Neurosci 2007; 26:1765-79. [PMID: 17883411 DOI: 10.1111/j.1460-9568.2007.05820.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Declined production and diminished dendritic growth of new dentate granule cells in the middle-aged and aged hippocampus are correlated with diminished concentration of fibroblast growth factor-2 (FGF-2). This study examined whether increased FGF-2 concentration in the milieu boosts both production and dendritic growth of new dentate granule cells in the middle-aged hippocampus. The FGF-2 or vehicle was infused into the posterior lateral ventricle of middle-aged Fischer (F)344 rats for 2 weeks using osmotic minipumps. New cells born during the first 12 days of infusions were labeled via daily intraperitoneal injections of 5'-bromodeoxyuridine (BrdU) and analysed at 10 days after the last BrdU injection. Measurement of BrdU(+) cells revealed a considerably enhanced number of new cells in the subgranular zone (SGZ) and granule cell layer (GCL) of the dentate gyrus (DG) ipsilateral to FGF-2 infusions. Characterization of beta-III tubulin(+) neurons among newly born cells suggested an increased addition of new neurons to the SGZ/GCL ipsilateral to FGF-2 infusions. Quantification of DG neurogenesis at 8 days post-infusions via doublecortin (DCX) immunostaining also revealed the presence of an enhanced DG neurogenesis ipsilateral to FGF-2 infusions. Furthermore, DCX(+) neurons in FGF-2-infused rats exhibited enhanced dendritic growth compared with their counterparts in vehicle-infused rats. Thus, subchronic infusion of FGF-2 is efficacious for stimulating an enhanced DG neurogenesis from neural stem/progenitor cells in the middle-aged hippocampus. As dentate neurogenesis is important for hippocampal-dependent learning and memory and DG long-term potentiation, strategies that maintain increased FGF-2 concentration during ageing may be beneficial for thwarting some of the age-related cognitive impairments.
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Affiliation(s)
- Kiranmai S Rai
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC 27710, USA
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167
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Hebda-Bauer EK, Luo J, Watson SJ, Akil H. Female CREBalphadelta- deficient mice show earlier age-related cognitive deficits than males. Neuroscience 2007; 150:260-72. [PMID: 18029102 DOI: 10.1016/j.neuroscience.2007.09.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Revised: 08/31/2007] [Accepted: 09/11/2007] [Indexed: 11/25/2022]
Abstract
Age-related changes in the hippocampus increase vulnerability to impaired learning and memory. Our goal is to understand how a genetic vulnerability to cognitive impairment can be modified by aging and sex. Mice with a mutation in the cAMP response element binding (CREB) protein gene (CREB(alphadelta-) deficient mice) have a mild cognitive impairment and show test condition-dependent learning and memory deficits. We tested three ages of CREB(alphadelta-) deficient and wild-type (WT) mice in two Morris water maze (MWM) protocols: four trials per day with a 3-5 min inter-trial interval (ITI) (MWM4) and two trials per day with a 1 min ITI (MWM2). All CREB(alphadelta-) deficient mice performed well in the easier MWM4, except for the aged females that performed poorly. In the harder MWM2, young male and female and middle-aged male CREB(alphadelta-) deficient mice performed well, but aged male and all middle-aged and aged female CREB(alphadelta-) deficient mice were impaired. These results show that mice with a genetic vulnerability to impaired learning and memory exhibit increased vulnerability with age that is most apparent among females. Thus, a genetic predisposition to cognitive impairment may render females more vulnerable than males to such deficits with age.
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Affiliation(s)
- E K Hebda-Bauer
- Molecular and Behavioral Neuroscience Institute, University of Michigan, 205 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
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168
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Abstract
The demographic changes in the foreseeable future stress the need for research on successful cognitive aging. Advancing age constitutes a primary risk factor for disease of the central nervous system most notably neurodegenerative disorders. The hippocampus is one of the brain regions that is prominently affected by neurodegeneration and functional decline even in what is still considered "normal aging". Plasticity is the basis for how the brain adapts to changes over time. The discovery of adult hippocampal neurogenesis has added a whole new dimension to research on structural plasticity in the adult and aging hippocampus. In this article, we briefly summarize and discuss recent findings on the regulation of adult neurogenesis with relevance to aging. Aging is an important co-variable for many regulatory mechanisms affecting adult neurogenesis but so far, only few studies have specifically addressed this interaction. We hypothesize that adult neurogenesis contributes to a neural reserve, i.e. the maintained potential for structural plasticity that allows compensation in situations of functional losses with aging. As such we propose that adult neurogenesis might contribute to the structural correlates of successful aging.
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Affiliation(s)
- Friederike Klempin
- Volkswagen Research Group at the Department of Experimental Neurology, Charité University Medicine Berlin, Schumannstr. 21-22, 10117 Berlin, Germany
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169
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Kuhn HG, Cooper-Kuhn CM, Boekhoorn K, Lucassen PJ. Changes in neurogenesis in dementia and Alzheimer mouse models: are they functionally relevant? Eur Arch Psychiatry Clin Neurosci 2007; 257:281-9. [PMID: 17639447 DOI: 10.1007/s00406-007-0732-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease and related dementias are devastating disorders that lead to the progressive decline of cognitive functions. Characteristic features are severe brain atrophy, paralleled by accumulation of beta amyloid and neurofibrillary tangles. With the discovery of neurogenesis in the adult brain, the hopes have risen that these neurodegenerative conditions could be overcome, or at least ameliorated, by the generation of new neurons. The location of the adult neurogenic zones in the hippocampus and the lateral ventricle wall, close to corpus callosum and neocortex, indicates strategic positions for potential repair processes. However, we also need to consider that the generation of new neurons is possibly involved in cognitive functions and could, therefore, be influenced by disease pathology. Moreover, aberrant neurogenic mechanisms could even be a part of the pathological events of neurodegenerative diseases. It is the scope of this review to summarize and analyze the recent data from neurogenesis research with respect to Alzheimer's disease and its animal models.
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Affiliation(s)
- H Georg Kuhn
- Center for Brain Repair and Rehabilitation, Institute for Neuroscience and Physiology, Göteborg University, Medicianregatan 11, 40530 Göteborg, Sweden.
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170
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Abstract
Certain regions of the adult brain have the ability for partial self-repair after injury through production of new neurons via activation of neural stem/progenitor cells (NSCs). Nonetheless, there is no evidence yet for pervasive spontaneous replacement of dead neurons by newly formed neurons leading to functional recovery in the injured brain. Consequently, there is enormous interest for stimulating endogenous NSCs in the brain to produce new neurons or for grafting of NSCs isolated and expanded from different brain regions or embryonic stem cells into the injured brain. Temporal lobe epilepsy (TLE), characterized by hyperexcitability in the hippocampus and spontaneous seizures, is a possible clinical target for stem cell-based therapies. This is because these approaches have the potential to curb epileptogenesis and prevent chronic epilepsy development and learning and memory dysfunction after hippocampal damage related to status epilepticus or head injury. Grafting of NSCs may also be useful for restraining seizures during chronic epilepsy. The aim of this review is to evaluate current knowledge and outlook pertaining to stem cell-based therapies for TLE. The first section discusses the behavior of endogenous hippocampal NSCs in human TLE and animal models of TLE and evaluates the role of hippocampal neurogenesis in the pathophysiology and treatment of TLE. The second segment considers the prospects for preventing or suppressing seizures in TLE using exogenously applied stem cells. The final part analyzes problems that remain to be resolved before initiating clinical application of stem cell-based therapies for TLE. Disclosure of potential conflicts of interest is found at the end of this article.
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Affiliation(s)
- Ashok K Shetty
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, North Carolina 27710, USA.
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171
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Pardon MC. Stress and ageing interactions: A paradox in the context of shared etiological and physiopathological processes. ACTA ACUST UNITED AC 2007; 54:251-73. [PMID: 17408561 DOI: 10.1016/j.brainresrev.2007.02.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Revised: 02/15/2007] [Accepted: 02/22/2007] [Indexed: 12/18/2022]
Abstract
Gerontology has made considerable progress in the understanding of the mechanisms underlying the ageing process and age-related neurodegenerative disorders. However, ways to improve quality of life in the elderly remain to be elucidated. It is now clear that stress and the ageing process share a number of underlying mechanisms bound in a very close, if not indissociable, relationship. The ageing process is regulated by the factors underlying the ability to adjust to stress, whilst stress has an influence on the life span and the quality of ageing. In addition, the ability to cope with stress in adulthood predicts life expectancy and quality of life at senescence. The ageing process and stress also share several common mechanisms, particularly in relation to the energy factor. Stress consumes energy and ageing may be considered as a cost of the energy expended to deal with the stressors to which the body is exposed throughout its lifetime. This suggests that the ageing process is associated with and/or a consequence of a long-lasting activation of the major stress responsive systems. However, despite common features, the interaction between stress and the ageing process gives rise to some paradoxes. Stress can either diminish or exacerbate the ageing process just as the ageing process can worsen or counter the effects of stress. There has been little attempt to understand how ageing and stress might interact to promote "successful" or pathological ageing. A key factor in this respect is the individual's ability to adapt to stress. Viewed from this angle, the quality of life of aged subjects may be improved through therapy designed to improve the tolerance to stress.
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Affiliation(s)
- Marie-Christine Pardon
- Institute of Neuroscience, School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK.
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172
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Velísková J, Velísek L. Beta-estradiol increases dentate gyrus inhibition in female rats via augmentation of hilar neuropeptide Y. J Neurosci 2007; 27:6054-63. [PMID: 17537977 PMCID: PMC6672257 DOI: 10.1523/jneurosci.0366-07.2007] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 05/02/2007] [Accepted: 05/05/2007] [Indexed: 11/21/2022] Open
Abstract
The dentate gyrus filters incoming activity into the hippocampus proper. It plays a role in learning and memory and in pathological states such as epilepsy. Some of hilar interneurons of the dentate gyrus express neuropeptide Y (NPY), which modulates granule cell activity. A subpopulation of the NPY-expressing inhibitory interneurons is sensitive to seizure-induced damage. Pretreatment with beta-estradiol in ovariectomized rats protects hilar interneurons against seizure-induced injury, including the NPY-containing damage-sensitive subpopulation. Here, we demonstrate that beta-estradiol enhances NPY expression within the hilar interneurons. In vitro paired-pulse stimulation of the mixed perforant path revealed beta-estradiol-induced augmentation of granule cell network inhibition, which at interstimulus intervals between 200 and 300 ms (corresponding to approximately 3-5 Hz) was NPY sensitive and involved Y1 receptors, whereas it was insensitive to GABA(B) or metabotropic glutamate receptor antagonists. Additionally, beta-estradiol pretreatment attenuated propagation of low-frequency (3.3 or 5 Hz) burst activity through the dentate gyrus. Scavenging endogenous NPY by intracerebroventricular administration of anti-NPY antibody accelerated kainic acid-induced seizure onset and increased seizure-induced neuronal damage in the hilus compared with rats treated with beta-estradiol alone. Together, we show that beta-estradiol upregulates hilar NPY and that this leads to enhancement in dentate gyrus inhibition of incoming frequencies between 3 and 5 Hz. Such frequencies are similar to the discharge frequencies recorded during seizure initiation in some patients with epilepsy. Thus, beta-estradiol-induced NPY-sensitive filtering of 3-5 Hz frequencies may be an important regulator of incoming seizure activity, but it could also serve a physiological purpose in modulating information flow into the hippocampus proper.
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Affiliation(s)
- Jana Velísková
- Saul R. Korey Department of Neurology, Laboratory of Developmental Epilepsy, Albert Einstein College of Medicine and the Einstein/Montefiore Comprehensive Epilepsy Management Center, Bronx, New York 10461, USA.
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173
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Hattiangady B, Shuai B, Cai J, Coksaygan T, Rao MS, Shetty AK. Increased dentate neurogenesis after grafting of glial restricted progenitors or neural stem cells in the aging hippocampus. Stem Cells 2007; 25:2104-17. [PMID: 17510219 DOI: 10.1634/stemcells.2006-0726] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Neurogenesis in the dentate gyrus (DG) declines severely by middle age, potentially because of age-related changes in the DG microenvironment. We hypothesize that providing fresh glial restricted progenitors (GRPs) or neural stem cells (NSCs) to the aging hippocampus via grafting enriches the DG microenvironment and thereby stimulates the production of new granule cells from endogenous NSCs. The GRPs isolated from the spinal cords of embryonic day 13.5 transgenic F344 rats expressing human alkaline phosphatase gene and NSCs isolated from embryonic day 9 caudal neural tubes of Sox-2:EGFP transgenic mice were expanded in vitro and grafted into the hippocampi of middle-aged (12 months old) F344 rats. Both types of grafts survived well, and grafted NSCs in addition migrated to all layers of the hippocampus. Phenotypic characterization revealed that both GRPs and NSCs differentiated predominantly into astrocytes and oligodendrocytic progenitors. Neuronal differentiation of graft-derived cells was mostly absent except in the dentate subgranular zone (SGZ), where some of the migrated NSCs but not GRPs differentiated into neurons. Analyses of the numbers of newly born neurons in the DG using 5'-bromodeoxyuridine and/or doublecortin assays, however, demonstrated considerably increased dentate neurogenesis in animals receiving grafts of GRPs or NSCs in comparison with both naïve controls and animals receiving sham-grafting surgery. Thus, both GRPs and NSCs survive well, differentiate predominantly into glia, and stimulate the endogenous NSCs in the SGZ to produce more new dentate granule cells following grafting into the aging hippocampus. Grafting of GRPs or NSCs therefore provides an attractive approach for improving neurogenesis in the aging hippocampus. Disclosure of potential conflicts of interest is found at the end of this article.
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174
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Mora F, Segovia G, del Arco A. Aging, plasticity and environmental enrichment: structural changes and neurotransmitter dynamics in several areas of the brain. ACTA ACUST UNITED AC 2007; 55:78-88. [PMID: 17561265 DOI: 10.1016/j.brainresrev.2007.03.011] [Citation(s) in RCA: 281] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 03/19/2007] [Accepted: 03/19/2007] [Indexed: 12/11/2022]
Abstract
Cajal was probably the first neurobiologist to suggest that plasticity of nerve cells almost completely disappeared during aging. However, we know today that neural plasticity is still present in the brain during aging. In this review we suggest that aging is a physiological process that occurs asynchronously in different areas of the brain and that the rate of that process is modulated by environmental factors and related to the neuronal-synaptic-molecular substrates of each area. We review here some of the most recent results on aging of the brain in relation to the plastic changes that occur in young and aged animals as a result of living in an enriched environment. We highlight the results from our own laboratory on the dynamics of neurotransmitters in different areas of the brain. Specifically we review first the effects of aging on neurons, dendrites, synapses, and also on molecular and functional plasticity. Second, the effects of environmental enrichment on the brain of young and aged animals. And third the effects of an enriched environment on the age-related changes in neurogenesis and in the extracellular concentrations of glutamate and GABA in hippocampus, and on dopamine, acetylcholine, glutamate and GABA under a situation of acute mild stress in the prefrontal cortex.
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Affiliation(s)
- Francisco Mora
- Department of Physiology, Faculty of Medicine, Universidad Complutense, Ciudad Universitaria, s/n, 28040 Madrid, Spain.
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175
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Tchantchou F, Xu Y, Wu Y, Christen Y, Luo Y. EGb 761 enhances adult hippocampal neurogenesis and phosphorylation of CREB in transgenic mouse model of Alzheimer's disease. FASEB J 2007; 21:2400-8. [PMID: 17356006 DOI: 10.1096/fj.06-7649com] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Standardized Ginkgo biloba extract EGb 761 exhibits beneficial effects to patients with Alzheimer's disease (AD). It was previously demonstrated that EGb 761 inhibits amyloid beta (Abeta) oligomerization in vitro, protects neuronal cells against Abeta toxicity, and improves cognitive defects in a mouse model of AD (Tg 2576). In this study, the neurogenic potential of EGb 761 and its effect on cAMP response element binding protein (CREB) were examined in a double transgenic mouse model (TgAPP/PS1). EGb 761 significantly increases cell proliferation in the hippocampus of both young (6 months) and old (22 months) TgAPP/PS1 mice, and the total number of neuronal precursor cells in vitro in a dose-dependent manner. Furthermore, Abeta oligomers inhibit phosphorylation of CREB and cell proliferation in the hippocampus of TgAPP/PS1 mice. Administration of EGb 761 reduces Abeta oligomers and restores CREB phosphorylation in the hippocampus of these mice. The present findings suggest that 1) enhanced neurogenesis by EGb 761 may be mediated by activation of CREB, 2) stimulation of neurogenesis by EGb 761 may contribute to its beneficial effects in AD patients and improved cognitive functions in the mouse model of AD, and 3) EGb 761 has therapeutic potential for the prevention and improved treatment of AD.
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Affiliation(s)
- Flaubert Tchantchou
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA
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176
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Spritzer MD, Galea LAM. Testosterone and dihydrotestosterone, but not estradiol, enhance survival of new hippocampal neurons in adult male rats. Dev Neurobiol 2007; 67:1321-33. [PMID: 17638384 DOI: 10.1002/dneu.20457] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Past research suggested that androgens may play a role in the regulation of adult neurogenesis within the dentate gyrus. We tested this hypothesis by manipulating androgen levels in male rats. Castrated or sham castrated male rats were injected with 5-Bromo-2'deoxyuridine (BrdU). BrdU-labeled cells in the dentate gryus were visualized and phenotyped (neural or glial) using immunohistochemistry. Castrated males showed a significant decrease in 30-day cell survival within the dentate gyrus but there was no significant change in cell proliferation relative to control males, indicating that androgens positively affect cell survival, but not cell proliferation. To examine the role of testosterone on hippocampal cell survival, males were injected with testosterone s.c. for 30 days starting the day after BrdU injection. Higher doses (0.5 and 1.0 mg/kg) but not a lower dose (0.25 mg/kg) of testosterone resulted in a significant increase in neurogenesis relative to controls. We next tested the role of testosterone's two major metabolites, dihydrotestosterone (DHT), and estradiol, upon neurogenesis. Thirty days of injections of DHT (0.25 and 0.50 mg/kg) but not estradiol (0.010 and 0.020 mg/kg) resulted in a significant increase in hippocampal neurogenesis. These results suggest that testosterone enhances hippocampal neurogenesis via increased cell survival in the dentate gyrus through an androgen-dependent mechanism.
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Affiliation(s)
- Mark D Spritzer
- Department of Psychology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
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177
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Patrylo PR, Williamson A. The effects of aging on dentate circuitry and function. PROGRESS IN BRAIN RESEARCH 2007; 163:679-96. [PMID: 17765745 DOI: 10.1016/s0079-6123(07)63037-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The central nervous system (CNS) undergoes a variety of anatomic, physiologic, and behavioral changes during aging. One region that has received a great deal of attention is the hippocampal formation due to the increased incidence of impaired spatial learning and memory with age. The hippocampal formation is also highly susceptible to Alzheimer's disease, ischemia/hypoxia, and seizure generation, the three most common aging-related neurological disorders. While data reveal that the dentate gyrus plays a key role in hippocampal function and dysfunction, the majority of electrophysiological studies that have examined the effects of age on the hippocampal formation have focused on CA3 and CA1. We perceive this to be an oversight and consequently will highlight data in this review which demonstrate an age-related disruption in dentate circuitry and function, and propose that these changes contribute to the decline in hippocampal-dependent behavior seen with "normal" aging.
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Affiliation(s)
- Peter R Patrylo
- Department of Physiology, Southern Illinois University School of Medicine Carbondale, IL 62901, USA.
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178
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Rao MS, Hattiangady B, Shetty AK. The window and mechanisms of major age-related decline in the production of new neurons within the dentate gyrus of the hippocampus. Aging Cell 2006; 5:545-58. [PMID: 17129216 DOI: 10.1111/j.1474-9726.2006.00243.x] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
While it is well known that production of new neurons from neural stem/progenitor cells (NSC) in the dentate gyrus (DG) diminishes greatly by middle age, the phases and mechanisms of major age-related decline in DG neurogenesis are largely unknown. To address these issues, we first assessed DG neurogenesis in multiple age groups of Fischer 344 rats via quantification of doublecortin-immunopositive (DCX+) neurons and then measured the production, neuronal differentiation and initial survival of new cells in the subgranular zone (SGZ) of 4-, 12- and 24-month-old rats using four injections (one every sixth hour) of 5'-bromodeoxyuridine (BrdU), and BrdU-DCX dual immunostaining. Furthermore, we quantified the numbers of proliferating cells in the SGZ of these rats using Ki67 immunostaining. Numbers of DCX+ neurons were stable at 4-7.5 months of age but decreased progressively at 7.5-9 months (41% decline), 9-10.5 months (39% decline), and 10.5-12 months (34% decline) of age. Analyses of BrdU(+) cells at 6 h after the last BrdU injection revealed a 71-78% decline in the production of new cells per day between 4-month-old rats and 12- or 24-month-old rats. Numbers of proliferating Ki67+ cells (putative NSCs) in the SGZ also exhibited similar (72-85%) decline during this period. However, the extent of both neuronal differentiation (75-81%) and initial 12-day survival (67-74%) of newly born cells was similar in all age groups. Additional analyses of dendritic growth of 12-day-old neurons revealed that newly born neurons in the aging DG exhibit diminished dendritic growth compared with their age-matched counterparts in the young DG. Thus, major decreases in DG neurogenesis occur at 7.5-12 months of age in Fischer 344 rats. Decreased production of new cells due to proliferation of far fewer NSCs in the SGZ mainly underlies this decline.
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Affiliation(s)
- Muddanna S Rao
- Department of Surgery (Division of Neurosurgery), Duke University Medical Center, Durham, NC 27710, USA
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179
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Hattiangady B, Shetty AK. Aging does not alter the number or phenotype of putative stem/progenitor cells in the neurogenic region of the hippocampus. Neurobiol Aging 2006; 29:129-47. [PMID: 17092610 PMCID: PMC3612500 DOI: 10.1016/j.neurobiolaging.2006.09.015] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 08/09/2006] [Accepted: 09/13/2006] [Indexed: 12/20/2022]
Abstract
To investigate whether dramatically waned dentate neurogenesis during aging is linked to diminution in neural stem/progenitor cell (NSC) number, we counted cells immunopositive for Sox-2 (a putative marker of NSCs) in the subgranular zone (SGZ) of young, middle-aged and aged F344 rats. The young SGZ comprised approximately 50,000 Sox-2+ cells and this amount did not diminish with aging. Quantity of GFAP+ cells and vimentin+ radial glia also remained stable during aging in this region. Besides, in all age groups, analogous fractions of Sox-2+ cells expressed GFAP (astrocytes/NSCs), NG-2 (oligodendrocyte-progenitors/NSCs), vimentin (radial glia), S-100beta (astrocytes) and doublecortin (new neurons). Nevertheless, analyses of Sox-2+ cells with proliferative markers insinuated an increased quiescence of NSCs with aging. Moreover, the volume of rat-endothelial-cell-antigen-1+ capillaries (vascular-niches) within the SGZ exhibited an age-related decline, resulting in an increased expanse between NSCs and capillaries. Thus, decreased dentate neurogenesis during aging is not attributable to altered number or phenotype of NSCs. Instead, it appears to be an outcome of increased quiescence of NSCs due to changes in NSC milieu.
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Affiliation(s)
- Bharathi Hattiangady
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC 27710, United States
- Medical Research and Surgery Services, Veterans Affairs Medical Center, Durham, NC 27705, United States
| | - Ashok K. Shetty
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC 27710, United States
- Medical Research and Surgery Services, Veterans Affairs Medical Center, Durham, NC 27705, United States
- Corresponding author at: Division of Neurosurgery, DUMC Box 3807, Duke University Medical Center, Durham, NC 27710, United States. Tel.: +1 919 286 0411x7096; fax: +1 919 286 4662., (A.K. Shetty)
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180
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Gallagher M, Colantuoni C, Eichenbaum H, Haberman RP, Rapp PR, Tanila H, Wilson IA. Individual differences in neurocognitive aging of the medial temporal lobe. AGE (DORDRECHT, NETHERLANDS) 2006; 28:221-33. [PMID: 22253491 PMCID: PMC3259151 DOI: 10.1007/s11357-006-9017-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 09/18/2006] [Accepted: 09/19/2006] [Indexed: 05/28/2023]
Abstract
A wide spectrum of outcomes in the cognitive effects of aging is routinely observed in studies of the elderly. Individual differences in neurocognitive aging are also a characteristic of other species, such as rodents and non-human primates. In particular, investigations at behavioral, brain systems, cellular and molecular levels of analysis have provided much information on the basis for individual differences in neurocognitive aging among healthy outbred rats. These findings are likely to be relevant to an understanding of the effects of aging on the brain, apart from neurodegenerative conditions, such as Alzheimer's disease, which do not naturally occur in rodents. Here we review and integrate those findings in a model supporting the concept that certain features of cognitive decline are caused by distributed alterations in the medial temporal lobe, which alter the information processing functions of the hippocampal formation. An additional emerging concept from this research is that preserved abilities at older ages may depend on adaptive changes in the hippocampal system that distinguish successful aging.
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Affiliation(s)
- Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Krieger School of Arts and Sciences, 103 Ames Hall, 3400 North Charles Street, Baltimore, MD 21218 USA
| | - Carlo Colantuoni
- Department of Biostatistics, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD USA
- Clinical Brain Disorders Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD USA
| | | | - Rebecca P. Haberman
- Department of Psychological and Brain Sciences, Johns Hopkins University, Krieger School of Arts and Sciences, Baltimore, MD USA
| | - Peter R. Rapp
- Mount Sinai School of Medicine, Neurobiology of Aging Laboratories, New York, NY USA
| | - Heikki Tanila
- Department of Neuroscience and Neurology, University of Kuopio, Kuopio, Finland
| | - Iain A. Wilson
- Division of Neuroscience, University of Edinburgh, Edinburgh, Scotland UK
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181
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Hwang IK, Yoo KY, Jung BK, Cho JH, Kim DH, Kang TC, Kwon YG, Kim YS, Won MH. Correlations between neuronal loss, decrease of memory, and decrease expression of brain-derived neurotrophic factor in the gerbil hippocampus during normal aging. Exp Neurol 2006; 201:75-83. [PMID: 16678162 DOI: 10.1016/j.expneurol.2006.02.129] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 02/19/2006] [Accepted: 02/21/2006] [Indexed: 11/28/2022]
Abstract
It is known that the hippocampus has vital functions in learning and memory, behavioral regulation, and activity-dependent synaptic plasticity, and that the hippocampus contains high levels of brain-derived neurotrophic factor (BDNF). In the present study, we followed age-dependent changes of BDNF immunoreactivity and protein level in the gerbil hippocampus to identify the correlation between BDNF and aging. BDNF immunoreactivity and its protein level significantly increased at postnatal month (PM) 12 in the hippocampus and thereafter reduced. At PM 24, BDNF immunoreactivity in the hippocampal CA1 region and dentate gyrus was similar to that in the PM 1 group, whereas BDNF immunoreactivity in the CA2/3 region at PM 24 was higher than that at PM 1. In the PM 24 group, an age-related neuronal loss and the decrease of reference and working memory were observed. In conclusion, our results suggest that observed reduction in BDNF and reference memory may be associated with age-dependent neuronal loss in the hippocampal CA1 region.
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Affiliation(s)
- In Koo Hwang
- Department of Anatomy, College of Medicine, Hallym University, Chunchon 200-702, South Korea
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182
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Lynch G, Rex CS, Gall CM. Synaptic plasticity in early aging. Ageing Res Rev 2006; 5:255-80. [PMID: 16935034 DOI: 10.1016/j.arr.2006.03.008] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Accepted: 03/30/2006] [Indexed: 01/25/2023]
Abstract
Studies of how aging affects brain plasticity have largely focused on old animals. However, deterioration of memory begins well in advance of old age in animals, including humans; the present review is concerned with the possibility that changes in synaptic plasticity, as found in the long-term potentiation (LTP) effect, are responsible for this. Recent results indicate that impairments to LTP are in fact present by early middle age in rats but only in certain dendritic domains. The search for the origins of these early aging effects necessarily involves ongoing analyses of how LTP is induced, expressed, and stabilized. Such work points to the conclusion that cellular mechanisms responsible for LTP are redundant and modulated both positively and negatively by factors released during induction of potentiation. Tests for causes of the localized failure of LTP during early aging suggest that the problem lies in excessive activity of a negative modulator. The view of LTP as having redundant and modulated substrates also suggests a number of approaches for reversing age-related losses. Particular attention will be given to the idea that induction of brain-derived neurotrophic factor, an extremely potent positive modulator, can be used to provide long periods of normal plasticity with very brief pharmacological interventions. The review concludes with a consideration of how the selective, regional deficits in LTP found in early middle age might be related to the global phenomenon of brain aging.
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Affiliation(s)
- Gary Lynch
- Department of Psychiatry and Human Behavior, Gillespie Neuroscience Research Facility, University of California at Irvine, Irvine, CA 92697, USA.
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183
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Rao MS, Hattiangady B, Reddy DS, Shetty AK. Hippocampal neurodegeneration, spontaneous seizures, and mossy fiber sprouting in the F344 rat model of temporal lobe epilepsy. J Neurosci Res 2006; 83:1088-105. [PMID: 16493685 DOI: 10.1002/jnr.20802] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The links among the extent of hippocampal neurodegeneration, the frequency of spontaneous recurrent motor seizures (SRMS), and the degree of aberrant mossy fiber sprouting (MFS) in temporal lobe epilepsy (TLE) are a subject of contention because of variable findings in different animal models and human studies. To understand these issues further, we quantified these parameters at 3-5 months after graded injections of low doses of kainic acid (KA) in adult F344 rats. KA was administered every 1 hr for 4 hr, for a cumulative dose of 10.5 mg/kg bw, to induce continuous stages III-V motor seizures for >3 hr. At 4 days post-KA, the majority of rats (77%) exhibited moderate bilateral neurodegeneration in different regions of the hippocampus; however, 23% of rats exhibited massive neurodegeneration in all hippocampal regions. All KA-treated rats displayed robust SRMS at 3 months post-KA, and the severity of SRMS increased over time. Analyses of surviving neurons at 5 months post-KA revealed two subgroups of rats, one with moderate hippocampal injury (HI; 55% of rats) and another with widespread HI (45%). Rats with widespread HI exhibited greater loss of CA3 pyramidal neurons and robust aberrant MFS than rats with moderate HI. However, the frequency of SRMS (approximately 3/hr) was comparable between rats with moderate and widespread HI. Thus, in comparison with TLE model using Sprague-Dawley rats (Hellier et al. [1998] Epilepsy Res. 31:73-84), a much lower cumulative dose of KA leads to robust chronic epilepsy in F344 rats. Furthermore, the occurrence of SRMS in this model is always associated with considerable bilateral hippocampal neurodegeneration and aberrant MFS. However, more extensive hippocampal CA3 cell loss and aberrant MFS do not appear to increase the frequency of SRMS. Because most of the features are consistent with mesial TLE in humans, the F344 model appears ideal for testing the efficacy of potential treatment strategies for mesial TLE.
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Affiliation(s)
- Muddanna S Rao
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, North Carolina 27710, USA
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184
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Rex CS, Lauterborn JC, Lin CY, Kramár EA, Rogers GA, Gall CM, Lynch G. Restoration of long-term potentiation in middle-aged hippocampus after induction of brain-derived neurotrophic factor. J Neurophysiol 2006; 96:677-85. [PMID: 16707719 PMCID: PMC1554892 DOI: 10.1152/jn.00336.2006] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Restoration of neuronal viability and synaptic plasticity through increased trophic support is widely regarded as a potential therapy for the cognitive declines that characterize aging. Previous studies have shown that in the hippocampal CA1 basal dendritic field deficits in the stabilization of long-term potentiation (LTP) are evident by middle age. The present study tested whether increasing endogenous brain-derived neurotrophic factor (BDNF) could reverse this age-related change. We report here that in middle-aged (8- to 10-mo-old) rats, in vivo treatments with a positive AMPA-type glutamate receptor modulator both increase BDNF protein levels in the cortical telencephalon and restore stabilization of basal dendritic LTP as assessed in acute hippocampal slices 18 h after the last drug treatment. These effects were not attributed to enhanced synaptic transmission or to facilitation of burst responses used to induce LTP. Increasing extracellular levels of BDNF by exogenous application to slices of middle-aged rats was also sufficient to rescue the stabilization of basal dendritic LTP. Finally, otherwise stable LTP in ampakine-treated middle-aged rats can be eliminated by infusion of the extracellular BDNF scavenger TrkB-Fc. Together these results indicate that increases in endogenous BDNF signaling can offset deficits in the postinduction processes that stabilize LTP.
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Affiliation(s)
- Christopher S Rex
- Department of Neurobiology and Behavior, University of California at Irvine, 92697-4292, USA
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185
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Abstract
Everyone ages, but only some will develop a neurodegenerative disorder in the process. Disease might occur when cells fail to respond adaptively to age-related increases in oxidative, metabolic and ionic stress, thereby resulting in the accumulation of damaged proteins, DNA and membranes. Determinants of neuronal vulnerability might include cell size and location, metabolism of disease-specific proteins and a repertoire of signal transduction pathways and stress resistance mechanisms. Emerging evidence on protein interaction networks that monitor and respond to the normal ageing process suggests that successful neural ageing is possible for most people, but also cautions that cures for neurodegenerative disorders are unlikely in the near future.
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Affiliation(s)
- Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224-6825, USA.
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