1
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Heng V, Zigmond M, Smeyne RJ. Neuroanatomical and neurochemical effects of prolonged social isolation in adult mice. Front Neuroanat 2023; 17:1190291. [PMID: 37662476 PMCID: PMC10471319 DOI: 10.3389/fnana.2023.1190291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 07/31/2023] [Indexed: 09/05/2023] Open
Abstract
Introduction As social animals, our health depends in part on interactions with other human beings. Yet millions suffer from chronic social isolation, including those in nursing/assisted living facilities, people experiencing chronic loneliness as well as those in enforced isolation within our criminal justice system. While many historical studies have examined the effects of early isolation on the brain, few have examined its effects when this condition begins in adulthood. Here, we developed a model of adult isolation using mice (C57BL/6J) born and raised in an enriched environment. Methods From birth until 4 months of age C57BL/6J mice were raised in an enriched environment and then maintained in that environment or moved to social isolation for 1 or 3 months. We then examined neuronal structure and catecholamine and brain derived neurotrophic factor (BDNF) levels from different regions of the brain, comparing animals from social isolation to enriched environment controls. Results We found significant changes in neuronal volume, dendritic length, neuronal complexity, and spine density that were dependent on brain region, sex, and duration of the isolation. Isolation also altered dopamine in the striatum and serotonin levels in the forebrain in a sex-dependent manner, and also reduced levels of BDNF in the motor cortex and hippocampus of male but not female mice. Conclusion These studies show that isolation that begins in adulthood imparts a significant change on the homeostasis of brain structure and chemistry.
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Affiliation(s)
- Vibol Heng
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA, United States
| | - Michael Zigmond
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Richard Jay Smeyne
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA, United States
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2
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Yau SY, Bettio L, Chiu J, Chiu C, Christie BR. Fragile-X Syndrome Is Associated With NMDA Receptor Hypofunction and Reduced Dendritic Complexity in Mature Dentate Granule Cells. Front Mol Neurosci 2019; 11:495. [PMID: 30705620 PMCID: PMC6344420 DOI: 10.3389/fnmol.2018.00495] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 12/27/2018] [Indexed: 12/11/2022] Open
Abstract
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. It is caused by the overexpansion of cytosine-guanine-guanine (CGG) trinucleotide in Fmr1 gene, resulting in complete loss of the fragile X mental retardation protein (FMRP). Previous studies using Fmr1 knockout (Fmr1 KO) mice have suggested that a N-methyl-D-aspartate receptors (NMDAR) hypofunction in the hippocampal dentate gyrus may partly contribute to cognitive impairments in FXS. Since activation of NMDAR plays an important role in dendritic arborization during neuronal development, we examined whether deficits in NMDAR function are associated with alterations in dendritic complexity in the hippocampal dentate region. The dentate granule cell layer (GCL) presents active postnatal neurogenesis, and consists of a heterogenous neuronal population with gradient ages from the superficial to its deep layer. Here, we show that neurons with multiple primary dendrites that reside in the outer GCL of Fmr1 KO mice display significantly smaller NMDAR excitatory post-synaptic currents (EPSCs) and a higher α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) to NMDA ratio in comparison to their wild-type counterparts. These deficits were associated with a significant decrease in dendritic complexity, with both dendritic length and number of intersections being significantly reduced. In contrast, although neurons with a single primary dendrite resided in the inner GCL of Fmr1 KO mice had a trend toward a reduction in NMDAR EPSCs and a higher AMPA/NMDA ratio, no alterations were found in dendritic complexity at this developmental stage. Our data indicate that the loss of FMRP causes NMDAR deficits and reduced dendritic complexity in granule neurons with multiple primary dendrites which are thought to be more mature in the GCL.
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Affiliation(s)
- Suk-Yu Yau
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, BC, Canada
| | - Luis Bettio
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, BC, Canada
| | - Jason Chiu
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, BC, Canada
| | - Christine Chiu
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, BC, Canada
| | - Brian R Christie
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, BC, Canada
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3
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Narducci R, Baroncelli L, Sansevero G, Begenisic T, Prontera C, Sale A, Cenni MC, Berardi N, Maffei L. Early impoverished environment delays the maturation of cerebral cortex. Sci Rep 2018; 8:1187. [PMID: 29352131 PMCID: PMC5775315 DOI: 10.1038/s41598-018-19459-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 12/27/2017] [Indexed: 12/26/2022] Open
Abstract
The influence of exposure to impoverished environments on brain development is unexplored since most studies investigated how environmental impoverishment affects adult brain. To shed light on the impact of early impoverishment on developmental trajectories of the nervous system, we developed a protocol of environmental impoverishment in which dams and pups lived from birth in a condition of reduced sensory-motor stimulation. Focusing on visual system, we measured two indexes of functional development, that is visual acuity, assessed by using Visual Evoked Potentials (VEPs), and VEP latency. In addition, we assessed in the visual cortex levels of Insulin-Like Growth Factor 1 (IGF-1) and myelin maturation, together with the expression of the GABA biosynthetic enzyme GAD67. We found that early impoverishment strongly delays visual acuity and VEP latency development. These functional changes were accompanied by a significant reduction of IGF-1 protein and GAD67 expression, as well as by delayed myelination of nerve fibers, in the visual cortex of impoverished pups. Thus, exposure to impoverished living conditions causes a significant alteration of developmental trajectories leading to a prominent delay of brain maturation. These results underscore the significance of adequate levels of environmental stimulation for the maturation of central nervous system.
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Affiliation(s)
- Roberta Narducci
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy.,Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, Area San Salvi - Pad. 26, I-50135, Florence, Italy
| | - Laura Baroncelli
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy.
| | - Gabriele Sansevero
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy.,Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, Area San Salvi - Pad. 26, I-50135, Florence, Italy
| | - Tatjana Begenisic
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy
| | - Concetta Prontera
- Fondazione G. Monasterio CNR-Regione Toscana, via Moruzzi 1, I-56124, Pisa, Italy
| | - Alessandro Sale
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy
| | - Maria Cristina Cenni
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy
| | - Nicoletta Berardi
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy.,Department of Neuroscience, Psychology, Drug Research and Child Health NEUROFARBA, University of Florence, Area San Salvi - Pad. 26, I-50135, Florence, Italy
| | - Lamberto Maffei
- Institute of Neuroscience, National Research Council (CNR), Via Moruzzi 1, I-56124, Pisa, Italy
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4
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Yau SY, Li A, Tong JB, Bostrom C, Christie BR, Lee TMC, So KF. Chronic corticosterone administration reduces dendritic complexity in mature, but not young granule cells in the rat dentate gyrus. Restor Neurol Neurosci 2018; 34:849-57. [PMID: 27567758 PMCID: PMC5345640 DOI: 10.3233/rnn-160662] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Background: Our previous work has shown that exposure to the stress hormone corticosterone (40 mg/kg CORT) for two weeks induces dendritic atrophy of pyramidal neurons in the hippocampal CA3 region and behavioral deficits. However, it is unclear whether this treatment also affects the dentate gyrus (DG), a subregion of the hippocampus comprising a heterogeneous population of young and mature neurons. Objective: We examined the effect of CORT treatment on the dendritic complexity of mature and young granule cells in the DG. Methods: We utilized a Golgi staining method to investigate the dendritic morphology and spine density of young neurons in the inner granular cell layer (GCL) and mature neurons in the outer GCL in response to CORT application. The expressions of glucocorticoid receptors during neuronal maturation were examined using Western blot analysis in a primary hippocampal neuronal culture. Results: Sholl analysis revealed that CORT treatment decreased the number of intersections and shortened the dendritic length in mature, but not young, granule cells. However, the spine density of mature and young neurons was not affected. Western blot analysis showed a progressive increase in the protein levels of glucocorticoid receptors (GRs) in the cultured primary hippocampal neurons during neuronal maturation. Conclusion: These data suggest that mature neurons are likely more vulnerable to chronic exposure to CORT; this may be due to their higher expression of GRs when compared to younger DG neurons.
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Affiliation(s)
- Suk-Yu Yau
- Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong SAR
| | - Ang Li
- Guangdong-Hong Kong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, China
| | - Jian-Bin Tong
- Department of Anesthesiology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Crystal Bostrom
- Division of Medical Sciences, The University of Victoria, British Columbia, Canada
| | - Brian R Christie
- Division of Medical Sciences, The University of Victoria, British Columbia, Canada
| | - Tatia M C Lee
- State Key Laboratory of Brain and Cognitive Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR.,Laboratory of Neuropsychology, The University of Hong Kong, Hong Kong SAR.,Laboratory of Cognitive Affective Neuroscience, The University of Hong Kong, Hong Kong SAR
| | - Kwok-Fai So
- Guangdong-Hong Kong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, China.,State Key Laboratory of Brain and Cognitive Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR.,Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR.,Co-innovation Center of Neuroregeneration, Jiangsu, China
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5
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Zhang B. Consequences of early adverse rearing experience(EARE) on development: insights from non-human primate studies. Zool Res 2017; 38:7-35. [PMID: 28271667 PMCID: PMC5368383 DOI: 10.13918/j.issn.2095-8137.2017.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 12/30/2016] [Indexed: 12/18/2022] Open
Abstract
Early rearing experiences are important in one's whole life, whereas early adverse rearing experience(EARE) is usually related to various physical and mental disorders in later life. Although there were many studies on human and animals, regarding the effect of EARE on brain development, neuroendocrine systems, as well as the consequential mental disorders and behavioral abnormalities, the underlying mechanisms remain unclear. Due to the close genetic relationship and similarity in social organizations with humans, non-human primate(NHP) studies were performed for over 60 years. Various EARE models were developed to disrupt the early normal interactions between infants and mothers or peers. Those studies provided important insights of EARE induced effects on the physiological and behavioral systems of NHPs across life span, such as social behaviors(including disturbance behavior, social deficiency, sexual behavior, etc), learning and memory ability, brain structural and functional developments(including influences on neurons and glia cells, neuroendocrine systems, e.g., hypothalamic-pituitary-adrenal(HPA) axis, etc). In this review, the effects of EARE and the underlying epigenetic mechanisms were comprehensively summarized and the possibility of rehabilitation was discussed.
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Affiliation(s)
- Bo Zhang
- Yunnan Key Laboratory of Primate Biomedical Research, Kunming Yunnan 650500, China; Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming Yunnan 650500, China; National Institute of Health, Bethesda, Maryland, USA.
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6
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Talani G, Biggio F, Licheri V, Locci V, Biggio G, Sanna E. Isolation Rearing Reduces Neuronal Excitability in Dentate Gyrus Granule Cells of Adolescent C57BL/6J Mice: Role of GABAergic Tonic Currents and Neurosteroids. Front Cell Neurosci 2016; 10:158. [PMID: 27378855 PMCID: PMC4904037 DOI: 10.3389/fncel.2016.00158] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 05/30/2016] [Indexed: 01/03/2023] Open
Abstract
Early-life exposure to stress, by impacting on a brain still under development, is considered a critical factor for the increased vulnerability to psychiatric disorders and abuse of psychotropic substances during adulthood. As previously reported, rearing C57BL/6J weanling mice in social isolation (SI) from their peers for several weeks, a model of prolonged stress, is associated with a decreased plasma and brain levels of neuroactive steroids such as 3α,5α-THP, with a parallel up-regulation of extrasynaptic GABAA receptors (GABAAR) in dentate gyrus (DG) granule cells compared to group-housed (GH) mice. In the present study, together with the SI-induced decrease in plasma concentration of both progesterone and 3α,5α-THP, and an increase in THIP-stimulated GABAergic tonic currents, patch-clamp analysis of DG granule cells revealed a significant decrease in membrane input resistance and action potential (AP) firing rate, in SI compared to GH mice, suggesting that SI exerts an inhibitory action on neuronal excitability of these neurons. Voltage-clamp recordings of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) revealed a SI-associated decrease in frequency as well as a shift from paired-pulse (PP) depression to PP facilitation (PPF) of evoked EPSCs, indicative of a reduced probability of glutamate release. Daily administration of progesterone during isolation reverted the changes in plasma 3α,5α-THP as well as in GABAergic tonic currents and neuronal excitability caused by SI, but it had only a limited effect on the changes in the probability of presynaptic glutamate release. Overall, the results obtained in this work, together with those previously published, indicate that exposure of mice to SI during adolescence reduces neuronal excitability of DG granule cells, an effect that may be linked to the increased GABAergic tonic currents as a consequence of the sustained decrease in plasma and hippocampal levels of neurosteroids. All these changes may be consistent with cognitive deficits observed in animals exposed to such type of prolonged stress.
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Affiliation(s)
- Giuseppe Talani
- Institute of Neuroscience, National Research Council of Italy Monserrato, Cagliari, Italy
| | - Francesca Biggio
- Department of Life and Environmental Sciences, Section of Neuroscience and Anthropology, University of Cagliari, Monserrato Italy
| | - Valentina Licheri
- Department of Life and Environmental Sciences, Section of Neuroscience and Anthropology, University of Cagliari, Monserrato Italy
| | - Valentina Locci
- Department of Biomedical Science, University of Sassari Sassari, Italy
| | - Giovanni Biggio
- Institute of Neuroscience, National Research Council of ItalyMonserrato, Cagliari, Italy; Department of Life and Environmental Sciences, Section of Neuroscience and Anthropology, University of Cagliari, MonserratoItaly
| | - Enrico Sanna
- Institute of Neuroscience, National Research Council of ItalyMonserrato, Cagliari, Italy; Department of Life and Environmental Sciences, Section of Neuroscience and Anthropology, University of Cagliari, MonserratoItaly
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7
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Wu KL, Wu CW, Tain YL, Huang LT, Chao YM, Hung CY, Wu JC, Chen SR, Tsai PC, Chan JY. Environmental stimulation rescues maternal high fructose intake-impaired learning and memory in female offspring: Its correlation with redistribution of histone deacetylase 4. Neurobiol Learn Mem 2016; 130:105-17. [DOI: 10.1016/j.nlm.2016.02.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 01/26/2016] [Accepted: 02/05/2016] [Indexed: 12/12/2022]
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8
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Rizzi S, Bianchi P, Guidi S, Ciani E, Bartesaghi R. Impact of environmental enrichment on neurogenesis in the dentate gyrus during the early postnatal period. Brain Res 2011; 1415:23-33. [PMID: 21885039 DOI: 10.1016/j.brainres.2011.08.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 07/25/2011] [Accepted: 08/03/2011] [Indexed: 02/06/2023]
Abstract
Accumulating evidence shows that environmental enrichment increases neurogenesis in the adult hippocampal dentate gyrus. The goal of the current study was to examine the effect of environmental enrichment on hippocampal neurogenesis during early life stages. We used as an animal model the guinea pig, a precocious rodent that is early independent from maternal care. Animals were assigned to either a standard (control) or an enriched environment a few days after birth (P5-P6). Between P14 and P17 animals received one daily bromodeoxyuridine (BrdU) injection, to label dividing cells, and were sacrificed either on P18, to evaluate cell proliferation or on P45, to evaluate cell survival and differentiation. In 18-day old enriched animals, there was a larger number of BrdU-positive cells compared to that found in controls. At P45, enriched animals had more surviving cells and more cells with a neuronal phenotype than controls. Unbiased stereology revealed that enriched animals had more granule cells (+37% at P18 and +31% at P45). Results show that environmental enrichment in the early postnatal period notably increases cell proliferation and survival, with a large increase in the number of neurons forming the granule cell layer. The impact of environmental enrichment in the early postnatal period emphasizes the relevance of extrinsic factors in the modulation of neurogenesis during critical time windows of hippocampal development.
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Affiliation(s)
- Simona Rizzi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40126 Bologna, Italy
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9
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Ali I, Salzberg MR, French C, Jones NC. Electrophysiological insights into the enduring effects of early life stress on the brain. Psychopharmacology (Berl) 2011; 214:155-73. [PMID: 21165736 DOI: 10.1007/s00213-010-2125-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 11/29/2010] [Indexed: 12/31/2022]
Abstract
Increasing evidence links exposure to stress early in life to long-term alterations in brain function, which in turn have been linked to a range of psychiatric and neurological disorders in humans. Electrophysiological approaches to studying these causal pathways have been relatively underexploited. Effects of early life stress on neuronal electrophysiological properties offer a set of potential mechanisms for these susceptibilities, notably in the case of epilepsy. Thus, we review experimental evidence for altered cellular and circuit electrophysiology resulting from exposure to early life stress. Much of this work focuses on limbic long-term potentiation, but other studies address alterations in electrophysiological properties of ion channels, neurotransmitter systems, and the autonomic nervous system. We discuss mechanisms which may mediate these effects, including influences of early life stress on key components of brain synaptic transmission, particularly glutamate, GABA and 5-HT receptors, and influences on neuroplasticity (primarily neurogenesis and synaptic density) and on neuronal network activity. The existing literature, although small, provides strong evidence that early life stress induces enduring, often robust effects on a range of electrophysiological properties, suggesting further study of enduring effects of early life stress employing electrophysiological methods and concepts will be productive in illuminating disease pathophysiology.
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Affiliation(s)
- Idrish Ali
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Melbourne, VIC, Australia
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10
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Zehr JL, Nichols LR, Schulz KM, Sisk CL. Adolescent development of neuron structure in dentate gyrus granule cells of male Syrian hamsters. Dev Neurobiol 2009; 68:1517-26. [PMID: 18792070 DOI: 10.1002/dneu.20675] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Hippocampal function, including spatial cognition and stress responses, matures during adolescence. In addition, hippocampal neuron structure is modified by gonadal steroid hormones, which increase dramatically at this time. This study investigated pubertal changes in dendritic complexity of dentate gyrus neurons. Dendrites, spines, and cell bodies of Golgi-impregnated neurons from the granule cell layer were traced in pre-, mid-, and late-pubertal male Syrian hamsters (21, 35, and 49 days of age). Sholl analysis determined the number of intersections and total dendritic length contained in concentric spheres set at 25-microm increments from the soma. Spine densities were quantified separately in proximal and distal segments of a subset of neurons used for the Sholl analysis. We found that the structure of neurons in the lower, but not upper, blade of the dentate gyrus changed during adolescence. The lower, infrapyramidal blade showed pruning of dendrites close to the cell body and increases in distal dendritic spine densities across adolescence. These data demonstrate that dentate gyrus neurons undergo substantial structural remodeling during adolescence and that patterns of maturation are region specific. Furthermore, these changes in dendrite structure, which alter the electrophysiological properties of granule cells, are likely related to the adolescent development of hippocampal-dependent cognitive functions such as learning and memory, as well as hippocampus-mediated stress responsivity.
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Affiliation(s)
- Julia L Zehr
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA.
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11
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Abstract
The mammalian brain contains a population of neurons that are continuously generated from late embryogenesis through adulthood-after the generation of almost all other neuronal types. This brain region-the hippocampal dentate gyrus-is in a sense, therefore, persistently immature. Postnatal and adult neurogenesis is likely an essential feature of the dentate, which is critical for learning and memory. Protracted neurogenesis after birth would allow the new cells to develop in conjunction with external events-but it may come with a price: while neurogenesis in utero occurs in a protected environment, children and adults are exposed to any number of hazards, such as toxins and infectious agents. Mature neurons might be resistant to such exposures, but new neurons may be vulnerable. Consistent with this prediction, in adult rodents seizures disrupt the integration of newly generated granule cells, whereas mature granule cells are comparatively unaffected. Significantly, abnormally interconnected cells may contribute to epileptogenesis and/or associated cognitive and memory deficits. Finally, studies increasingly indicate that new granule cells are extremely sensitive to a host of endogenous and exogenous factors, raising the possibility that disrupted granule cell integration may be a common feature of many neurological diseases.
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Affiliation(s)
- Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
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12
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Darmopil S, Petanjek Z, Mohammed AH, Bogdanović N. Environmental enrichment alters dentate granule cell morphology in oldest-old rat. J Cell Mol Med 2008; 13:1845-1856. [PMID: 19175692 DOI: 10.1111/j.1582-4934.2008.00560.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The hippocampus of aged rats shows marked age-related morphological changes that could cause memory deficits. Experimental evidence has established that environmental enrichment attenuates memory deficits in aged rats. We therefore studied whether environmental enrichment produces morphological changes on the dentate granule cells of aged rats. Fifteen male Sprague-Dawley rats, 24 months of age, were randomly distributed in two groups that were housed under standard (n = 7) or enriched (n = 8) environmental conditions for 26 days. Quantitative data of dendritic morphology from dentate gyrus granule cells were obtained on Golgi-Cox stained sections. Environmental enrichment significantly increased the complexity and size of dendritic tree (total number of segments increased by 61% and length by 116%), and spine density (88% increase). There were large interindividual differences within the enriched group, indicating differential individual responses to environmental stimulation. Previous studies in young animals have shown changes produced by environmental enrichment in the morphology of dentate gyrus granule cells. The results of the present study show that environmental enrichment can also produce changes in dentate granule cell morphology in the senescent brain. In conclusion, the hippocampus retains its neuroplastic capacity during aging, and enriched environmental housing conditions can attenuate age-related dendritic regression and synaptic loss, thus preserving memory functions.
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Affiliation(s)
- Sanja Darmopil
- Department for Neurobiology, Caring Science and Society, Division of Clinical Geriatrics, Karolinska Institutet Science Park, Novum Research Park, Stockholm, Sweden.,Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Šalata, Zagreb, Croatia
| | - Zdravko Petanjek
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Šalata, Zagreb, Croatia.,Department of Anatomy, School of Medicine, University of Zagreb, Šalata, Zagreb, Croatia
| | - Abdul H Mohammed
- Department for Neurobiology, Caring Science and Society, Division of Clinical Geriatrics, Karolinska Institutet Science Park, Novum Research Park, Stockholm, Sweden.,School of Social Sciences, Växjö University, Växjö, Sweden
| | - Nenad Bogdanović
- Department for Neurobiology, Caring Science and Society, Division of Clinical Geriatrics, Karolinska Institutet Science Park, Novum Research Park, Stockholm, Sweden.,Wyeth Pharmaceutical, Global Medical Team - Neuroscience, Maidenhead, London, UK
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13
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Bindu B, Alladi PA, Mansooralikhan BM, Srikumar BN, Raju TR, Kutty BM. Short-term exposure to an enriched environment enhances dendritic branching but not brain-derived neurotrophic factor expression in the hippocampus of rats with ventral subicular lesions. Neuroscience 2006; 144:412-23. [PMID: 17097239 DOI: 10.1016/j.neuroscience.2006.09.057] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 09/18/2006] [Accepted: 09/20/2006] [Indexed: 01/08/2023]
Abstract
Environmental enrichment promotes structural and behavioral plasticity in the adult brain. We have evaluated the efficacy of enriched environment on the dendritic morphology and brain-derived neurotrophic factor (BDNF) expression in the hippocampus of ventral subicular-lesioned rats. Bilateral ventral subicular lesion has significantly reduced the dendritic architecture and spine density of hippocampal pyramidal neurons. The lesioned rats exposed to enriched housing for 10 days showed a significant degree of morphological plasticity in terms of enhanced dendritic branching and spine density. However, the BDNF expression in the hippocampus remained unchanged following subicular lesion and following environmental enrichment. We suggest the participation of other neurotrophic factors in mediating the synaptic plasticity events following exposure to environmental enrichment in ventral subicular-lesioned rats.
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Affiliation(s)
- B Bindu
- Department of Neurophysiology, National Institute of Mental Health and Neuro Sciences, Hosur Road, Bangalore, India
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14
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Bartesaghi R, Raffi M, Ciani E. Effect of early isolation on signal transfer in the entorhinal cortex–dentate–hippocampal system. Neuroscience 2006; 137:875-90. [PMID: 16325342 DOI: 10.1016/j.neuroscience.2005.10.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 09/29/2005] [Accepted: 10/18/2005] [Indexed: 11/24/2022]
Abstract
Deprivation of socio-sensory interactions during early life impairs brain function in adulthood. In previous investigations we showed that early isolation severely affects neuron development in several structures of the hippocampal region, including the entorhinal cortex. In the present study we investigated the effects of early isolation on signal processing along the entorhinal cortex-dentate-CA3-CA1 system, a major memory circuit of the hippocampal region. Male and female guinea-pigs were assigned at 6-7 days of age to either a social or an isolated environment. At 90-100 days of age the animals were anesthetized and field potentials were recorded from the entorhinal cortex-dentate-CA3-CA1 circuit, driven by dorsal psalterium commissural volleys. Analysis of the input-output function in the different structures showed that in isolated males there was a small reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in layer II of the entorhinal cortex. No changes occurred in isolated females. In isolated males and females there was a reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in the dentate gyrus, CA3 and CA1, but this effect was larger in males. In isolated males, but not in females, the population spike/population excitatory postsynaptic potential ratio was reduced in all investigated structures, indicating that in males the size of the discharged neuron population was reduced more than due to the decreased input. Results show that isolation reduces the synaptic function in the whole entorhinal cortex-dentate gyrus-CA3-CA1 system. While the entorhinal cortex was moderately impaired, the dentate-hippocampal system was more severely affected. The impairment in the signal transfer along the entorhinal cortex-dentate gyrus-CA3-CA1 system was heavier in males, confirming the larger susceptibility of this sex to early experience. This work provides evidence that malfunctioning of a major hippocampal network may underlie the learning deficits induced by impoverished surroundings during early life.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40126 Bologna, Italy.
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Guidi S, Severi S, Ciani E, Bartesaghi R. Sex differences in the hilar mossy cells of the guinea-pig before puberty. Neuroscience 2006; 139:565-76. [PMID: 16458436 DOI: 10.1016/j.neuroscience.2005.12.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 11/17/2005] [Accepted: 12/10/2005] [Indexed: 02/05/2023]
Abstract
Numerous sex differences have been detected in the morphology of the dentate and hippocampal neurons and hippocampus-dependent memory functions. The aim of the present study was to ascertain whether the mossy cells, an interneuron population forming a recurrent excitatory circuit with the dentate granule cells, are sexually dimorphic. The brains of juvenile (15-16 days old) and peripubescent (45-46 days old) male and female guinea-pigs were Golgi-Cox stained. Mossy cells were sampled from the hilus in the septal third of the dentate gyrus and their dendritic tree and somata were analyzed. The analysis was separately conducted on mossy cells with soma located in the portions of the hilus that face the upper blade (upper hilus) and lower blade (lower hilus), respectively. The mossy cells in the upper hilus were found to be sexually dimorphic in both juvenile and peripubescent animals. At both ages females had a larger dendritic tree than males. This difference was due to a greater mean branch length and, in peripubescent animals, also to a greater number of branches. In juvenile males, the spines on the proximal dendrites (thorny excrescences) had a greater density than in females. No differences in spine density were present in peripubescent animals. Unlike the mossy cells in the upper hilus, the mossy cells in the lower hilus showed very few sex differences in juvenile animals and no differences in peripubescent animals. The few differences favored females, that had more proximal branches and a greater spine density on the distal dendrites than males. The results show that the mossy cells of the guinea-pig are sexually dimorphic prior to puberty. Extending a previous investigation, the present data provide evidence that sex differences are mainly confined to the dentate region corresponding to the upper blade and upper hilus. The observed segregation of the sexual dimorphism in the upper blade/upper hilus suggests that this region might underlie the sexual dimorphism in hippocampus-dependent memory functions.
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Affiliation(s)
- S Guidi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40126 Bologna, Italy
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16
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Rizzi S, Bianchi P, Guidi S, Ciani E, Bartesaghi R. Neonatal isolation impairs neurogenesis in thedentate gyrus of the guinea pig. Hippocampus 2006; 17:78-91. [PMID: 17143902 DOI: 10.1002/hipo.20247] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the current study we examined the effects of early isolation rearing on cell proliferation, survival and differentiation in the dentate gyrus of the guinea pig. Animals were assigned to either a standard (control) or an isolated environment a few days after birth (P5-P6), taking advantage of the precocious independence from maternal care of the guinea pig. On P14-P17 animals received one daily bromodeoxyuridine injection, to label dividing cells, and were sacrificed either on P18, to evaluate cell proliferation or on P45, to evaluate cell survival and differentiation. In P18 isolated animals we found a reduced cell proliferation (-35%) compared to controls and a lower expression of brain-derived neurotrophic factor (BDNF). Though in absolute terms P45 isolated animals had less surviving cells, they showed no differences in survival rate and phenotype percent distribution compared to controls. Looking at the location of the new neurons, we found that while in control animals 76% of them had migrated to the granule cell layer, in isolated animals only 55% of the new neurons had reached this layer. Examination of radial glia cells of P18 and P45 animals by vimentin immunohistochemistry showed that in isolated animals radial glia cells were reduced in density and had less and shorter processes. Granule cell count revealed that P45 isolated animals had less (-42%) granule cells than controls. Results show that isolation rearing reduces hippocampal cell proliferation, likely by reducing BDNF expression and hampers migration of the new neurons to the granule cell layer, likely by altering density/morphology of radial glia cells. The large reduction in granule cell number following isolation rearing emphasizes the role of environmental cues as relevant modulators of neurogenesis.
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Affiliation(s)
- Simona Rizzi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Bologna, Italy
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17
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Guidi S, Ciani E, Severi S, Contestabile A, Bartesaghi R. Postnatal neurogenesis in the dentate gyrus of the guinea pig. Hippocampus 2005; 15:285-301. [PMID: 15515010 DOI: 10.1002/hipo.20050] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In all species examined, the dentate gyrus develops over an extended period that begins during gestation and continues up to adulthood. The aim of this study was to investigate the pattern of postnatal cell production in the dentate gyrus of the guinea pig, a rodent whose brain development has features more closely resembling the human condition than the most commonly used rodents (rat and mouse). Animals of different postnatal (P) ages received one or multiple injections of bromodeoxyuridine (BrdU), and the number of labeled cells in the dentate gyrus was counted after time intervals of 24 h or longer. The total granule cell number and the volume of the granule cell layer were evaluated in Nissl-stained brain sections from P1 and P30 animals. P1-P5 animals were treated with MK-801 to analyze the effect of NMDA receptor blockade on cell proliferation. Cell production occurred at a high rate (9,000-13,000 labeled cells 24 h after one injection) from P1 to P20, with a peak at 3-6 days of age, and then slowly declined from P20 to P30. The production of new cells continued in adult animals, although at a much-reduced rate (400 cells 24 h after one injection). About 20% of the labeled cells survived after a 17-day period and most (60%) of these cells had a neuronal phenotype. The total number of granule cells increased over the first postnatal month; in 30-day-old animals, it was 20% greater than in 1-day-old animals. Administration of MK-801 to P1-P5 animals caused an increase in cell proliferation restricted to the dorsal dentate gyrus. The present data show that, although the guinea pig dentate gyrus develops largely before birth, the production of new neurons continues at a high rate during the first postnatal month, leading to a considerable increase in cell number. This developmental pattern, resembling the human and nonhuman primate condition, may make the guinea pig a useful rodent model in developmental studies on dentate gyrus neurogenesis.
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Affiliation(s)
- Sandra Guidi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Bologna, Italy
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Busche A, Bagorda A, Lehmann K, Neddens J, Teuchert-Noodt G. The maturation of the acetylcholine system in the dentate gyrus of gerbils (Meriones unguiculatus) is affected by epigenetic factors. J Neural Transm (Vienna) 2005; 113:113-24. [PMID: 15959847 DOI: 10.1007/s00702-005-0317-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2005] [Accepted: 04/09/2005] [Indexed: 12/31/2022]
Abstract
The current study investigated the influence of impoverished rearing (IR) conditions and a single early methamphetamine challenge (MA; 50 mg/kg i.p.) on day 14 on the postnatal maturation of acetylcholinesterase-positive (AChE+) fibres in the hippocampal dentate gyrus (DG) of gerbils (Meriones unguiculatus). The layer-specific densities of histochemically stained AChE+ fibres were quantified in two planes of the left and right DG in young adults (day 90). Compared to enriched reared (ER) animals, the AChE+ fibre densities turned out to be higher in both the septal and the temporal plane of both hemispheres in saline treated IR and MA treated ER gerbils. The temporal plane was slightly more affected than the septal plane. In IR animals, MA treatment selectively diminished the AChE+ fibre densities in the subgranular layer of both left and right temporal DG. In conclusion, the maturation of AChE+ fibres is vulnerable to both rearing conditions and early MA challenge. The results correlate with our previous studies on the dentate cell proliferation rates and the serotonergic innervation, two parameters which are similarly affected by the experimental design. Thus, disturbances of the ACh system may impair the hippocampal plasticity and hippocampus-related cognitive and emotional function.
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Affiliation(s)
- A Busche
- Department of Neuroanatomy, Faculty of Biology, University of Bielefeld, Germany
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Gomez-Pinilla F, Vaynman S. A “deficient environment” in prenatal life may compromise systems important for cognitive function by affecting BDNF in the hippocampus. Exp Neurol 2005; 192:235-43. [PMID: 15755541 DOI: 10.1016/j.expneurol.2004.12.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 11/09/2004] [Accepted: 12/01/2004] [Indexed: 10/25/2022]
Abstract
The intrauterine environment has the capacity to mold the prenatal nervous system. Particularly, recent findings show that an adverse prenatal environment produces structural defects of the hippocampus, a critical area sub-serving learning and memory functions. These structural changes are accompanied by a disruption in the normal expression pattern of brain-derived neurotrophic factor (BDNF) and its cognate tyrosine kinase B (TrkB) receptor. The important role that the BDNF system plays in neural modeling and learning and memory processes suggests that fetal exposure to unfavorable intrauterine conditions may compromise proper cognitive function in adult life. These findings have implications for disorders that involve a dysfunction in the BDNF system and are accompanied by cognitive deficits.
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Affiliation(s)
- F Gomez-Pinilla
- Division of Neurosurgery, Department of Physiology Science, UCLA, 621 Charles E. Young Dr, Los Angeles, CA 90095, USA.
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Severi S, Guidi S, Ciani E, Bartesaghi R. Sex differences in the stereological parameters of the hippocampal dentate gyrus of the guinea-pig before puberty. Neuroscience 2005; 132:375-87. [PMID: 15802190 DOI: 10.1016/j.neuroscience.2004.12.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2004] [Indexed: 01/21/2023]
Abstract
Studies in rats and mice have shown several sex-dependent functional and structural differences in the hippocampal region, a brain structure playing a key role in learning and memory. The aim of the present study was to establish whether sex differences exist prior to puberty in the stereological parameters of the dentate gyrus in the guinea-pig, a long-gestation rodent, whose brain is at a more advanced stage of maturation at birth than the rat and mouse. The number of granule cells and volumes of the granule cell layer, molecular layer and hilus were evaluated in Nissl-stained brains of neonatal (15-16 days old) and peripubescent (45-46 days old) guinea-pigs. Based on a pilot study, the optical disector method was preferred to the optical fractionator method to estimate cell number. For volume (Vref) estimation with the Cavalieri principle, contour tracing was preferred to the point counting method, as the latter appeared to underestimate volumes. The results showed that neonatal males had more granule cells than females in both the dorsal and ventral dentate gyrus and a larger volume in all layers. Peripubescent males had a larger volume of the granule cell layer than females in both the dorsal and ventral dentate gyrus, more granule cells in the ventral dentate gyrus, a larger volume of the hilus in both the dorsal and ventral dentate gyrus and a larger volume of the molecular layer in the ventral dentate gyrus. The results show that sex differences are present in the guinea-pig dentate gyrus prior to puberty and go in the same direction at both investigated ages, with males exhibiting more granule cells and larger volumes than females. The widespread distribution of these sex differences suggests that in the guinea-pig, similarly to other rodents, hippocampus-dependent functions may be sexually dimorphic.
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Affiliation(s)
- S Severi
- Dipartimento di Fisiologia, Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40126 Bologna, Italy
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21
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Abstract
Previous work showed that isolation rearing produces remarkable changes in the dendritic pattern and soma of the principal neurons in the dentate gyrus and hippocampal fields CA3 and CA1 of the guinea-pig. The aim of the present study was to obtain information about the effects of early postnatal isolation on neuron morphology in field CA2, the "resistant sector" of the hippocampal formation. Male and female guinea-pigs were assigned at 6-7 days of age to either a control (social) or an isolated environment where they remained for 80-90 days. The apical and basal dendritic trees and the soma of CA2 pyramidal neurons were analyzed and quantified in Golgi-stained brains. The results showed that in both males and females early isolation caused no effects on the length and dendritic branching density of the apical tree of field CA2 pyramidal neurons. In males but not in females isolation caused a spine density reduction in the inner apical tree. Isolation notably influenced the morphology of the basal tree, but in males only. Isolated males exhibited a significant reduction in the length of the basal tree and number of dendritic branches accompanied by a reduction in spine density. The comparison of animals reared in the same environment showed that in the control environment males had more apical and basal dendritic branches and a larger neuron soma than females. In the isolated environment the sex differences in the apical tree disappeared and those in the basal tree changed direction.The results demonstrate structural changes in field CA2 pyramidal neurons following neonatal isolation, with a specific reactivity to environment of the basal tree of males. The dendritic atrophy in field CA2 of isolated males is in line with previous evidence that males react to isolation mainly with dendritic atrophy, though field CA2 neurons appear to be less damaged than those of the other hippocampal fields. This is in line with the resistance of this field to neurodegeneration. The absence of structural changes in field CA2 of isolated females confirms, once again, that males are more liable to be endangered by early isolation than females.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40127, Bologna, Italy.
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22
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Bartesaghi R. Effect of early isolation on the synaptic function in the dentate gyrus and field CA1 of the guinea pig. Hippocampus 2004; 14:482-98. [PMID: 15224984 DOI: 10.1002/hipo.10201] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We previously reported that neonatal isolation shapes neuron morphology remarkably in the dentate gyrus and hippocampus of the guinea pig, a precocial rodent whose brain is at an advanced stage of maturation at birth. The aim of the present work was to investigate the effects of early isolation on the physiology of the hippocampal trisynaptic circuit. Male and female guinea pigs were assigned at 6-7 days of age to either a social or an isolated environment. After 90-100 days, the animals were anesthetized and electrophysiological experiments were carried out. The monosynaptic response evoked by medial perforant path stimulation in the dentate gyrus (DG) and the following response trisynaptically evoked in field CA1 by the DG-CA3 system were evaluated with several stimulus protocols: (1) current source-density (CSD) analysis; (2) input/output function; (3) paired-pulse potentiation (PPP); and (4) long-term potentiation (LTP). Isolated animals exhibited a reduction in the magnitude of the current sinks in the middle molecular layer and granule cell layer of the DG and in the input/output function of the granule cell population excitatory postsynaptic potential (EPSP) and population spike (PS) over a wide range of stimuli. The latter effect was larger in males. The ratio between the PS and EPSP of the granule cells was reduced in isolated compared to control males, but the opposite occurred in females. Isolation affected PPP of the granule cell response in males only, causing a larger facilitation of the PS. No isolation-related effects were found in the magnitude of the LTP of the DG response in either sex. Isolated animals exhibited a reduction in the current sinks in stratum radiatum and stratum pyramidale of field CA1 and in the input/output function of the EPSP and PS of field CA1. These effects were larger in males. The results show that early isolation causes a reduction in the synaptic function of the DG-CA3-CA1 system, driven by perforant path volleys. The isolation-induced impairment in signal processing along the hippocampal network suggests that the outcome of early isolation may be an impairment in the memory functions in which the entorhinal-hippocampal system plays a key role.
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Affiliation(s)
- Renata Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Bologna, Italy.
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Bartesaghi R, Raffi M, Severi S. Effects of early isolation on layer II neurons in the entorhinal cortex of the guinea pig. Neuroscience 2003; 120:721-32. [PMID: 12895512 DOI: 10.1016/s0306-4522(03)00354-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies showed that early environmental conditions severely affect the morphology of the granule cells in the hippocampal dentate gyrus and pyramidal neurons in fields CA3 and CA1. The aim of the present study was to determine whether early isolation affects neuron morphology in layer II of the entorhinal cortex, from which the perforant path to the dentate gyrus and CA3 takes its origin. Male and female guinea pigs were assigned at 6-7 days of age to either a control (social) or an isolated environment where they remained for 80-90 days. The brains were Golgi-Cox stained and neurons were sampled from layer II of the entorhinal cortex. Morphometric analysis was carried out on star cells, the most abundant neuron population. Isolated males had star cells with less dendritic branches, a shorter dendritic length and a smaller dendritic spine density than control males. In contrast, isolated females had more dendritic branches than control females, though this difference was of small magnitude. While isolated males had star cells with a smaller soma than control males, isolated females had a soma larger than control females. In both environments sex differences were found in the star cell morphology. In the control environment males had more dendritic branches, a greater dendritic length, a larger soma but a smaller spine density than females. In the isolated environment males had less branches, a shorter dendritic length, a smaller spine density and a smaller soma than females. The results indicate that early isolation affects the structure of the star cells in the entorhinal cortex and that males and females react to isolation in an opposite manner. A similar sexually dimorphic response to early isolation was previously observed in the dentate gyrus and fields CA3 and CA1. The presence of widespread effects of isolation in the entorhinal cortex and numerous hippocampal structures suggests that the outcome of early isolation might be a change in learning and memory functions requiring the hippocampal region.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40127 Bologna, Italy.
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Bartesaghi R, Guidi S, Severi S, Contestabile A, Ciani E. Sex differences in the hippocampal dentate gyrus of the guinea-pig before puberty. Neuroscience 2003; 121:327-39. [PMID: 14521992 DOI: 10.1016/s0306-4522(03)00434-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The aim of the present research was to ascertain the presence of sex differences in the hippocampal dentate gyrus of the guinea-pig, a long-gestation rodent which gives birth to mature young and whose brain is at a more advanced stage of maturation at birth than that of the rat and mouse. The brains of neonatal (15-16 days old) and prepubescent (45-46 days old) male and female guinea pigs were Golgi-Cox stained. Granule cells were sampled from the upper (suprapyramidal) and lower (infrapyramidal) blade of the septal dentate gyrus and their dendritic tree and soma were measured. The analysis was conducted separately on granule cells with soma in the superficial (superficial granule cells) and deep (deep granule cells) half of the granule cell layer. Numerous sex differences were found in the upper blade of the dentate gyrus. Neonatal males had more dendritic branches than females in the innermost dendritic tree of both superficial and deep granule cells, but females had more branches over the middle/outer dendritic tree and a longer dendritic length. In prepubescent animals, the sex difference in the middle dendritic tree of the superficial granule cells changed direction, with males having more branches than females. In the deep granule cells, the sex differences were similar to those in neonatal animals. In both granule cell types, the dendritic length was similar in the two sexes. While no sex differences were found in dendritic spine density in neonatal animals, in prepubescent animals spine density was greater in females. In the lower blade the granule cells showed very few sex differences in both neonatal and prepubescent animals. This study shows wide dynamically changing sex differences in the granule cells located in the upper blade of the septal dentate gyrus, but almost no differences in the lower blade. These results demonstrate that sex differences are not ubiquitous in the dentate gyrus and suggest that the lower blade, unlike the upper blade, might be involved in non-sexually dimorphic behaviors.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta San Donato 2, I-40127 Bologna, Italy.
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25
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Bartesaghi R, Severi S, Guidi S. Effects of early environment on pyramidal neuron morphology in field CA1 of the guinea-pig. Neuroscience 2003; 116:715-32. [PMID: 12573714 DOI: 10.1016/s0306-4522(02)00753-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We previously demonstrated that early isolation has profound effects on the morphology of the dentate granule cells and field CA3 pyramidal neurons. Aim of the present study was to analyze the effects of early environment on the morphology of field CA1 pyramidal neurons, the third element of the hippocampal trisynaptic circuit. The dendritic trees and the soma of field CA1 pyramidal neurons were quantified in Golgi-stained brains of guinea-pigs of both sexes raised in either a social or an isolated environment. Based on the different pattern of the apical dendritic tree two major classes of CA1 pyramidal neurons were recognized (monotufted neurons and bitufted neurons). In males isolation induced in both neuron types a decrease in the number of low order apical branches but in the apical tree of the monotufted neurons isolation induced an increase in the number of intermediate order branches and dendritic length. In isolated females the apical tree of the monotufted neurons showed a very scarce atrophy. In contrast, the apical tree of the bitufted neurons from isolated females showed a decrease in the number of low and intermediate order branches and dendritic length. In isolated males the basal tree of the bitufted neurons had a large decrease in the total number of branches and dendritic length. In contrast, in isolated females the basal tree of both neuron types showed an increase in the number of low order branches. In males but not in females isolation caused a reduction in the soma dimensions of both neuron types. No isolation-induced changes were observed in dendritic spine density in either the apical or basal dendrites. The results demonstrate remarkable structural changes in CA1 pyramidal neurons following early isolation and a different reactivity to environment of the two CA1 pyramidal neuron types, their apical and basal trees and the two sexes. The neuroanatomical changes caused by isolation in field CA1 and in the two other elements of the trisynaptic circuit are likely to be associated with changes in the physiology of the hippocampal formation and in cognitive processes such as learning and memory in which the hippocampal formation plays a pivotal role.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Italy.
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26
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Dieni S, Rees S. Dendritic morphology is altered in hippocampal neurons following prenatal compromise. JOURNAL OF NEUROBIOLOGY 2003; 55:41-52. [PMID: 12605458 DOI: 10.1002/neu.10194] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Chronic placental insufficiency (CPI), a known cause of intrauterine growth restriction, can lead to structural alterations in the developing brain that might underlie postnatal neurological deficits. We have previously demonstrated significant reductions in the volumes of hippocampal neuropil layers in fetal guinea pig brains following experimentally induced growth restriction. To determine the components of the neuropil affected in the brains of growth restricted (GR) fetuses, the dendritic morphology of CA1 pyramidal neurons and dentate granule cells was examined. CPI was induced by unilateral uterine artery ligation in pregnant guinea pigs at midgestation (term approximately 67 days). Hippocampi from control and GR fetuses were stained using the Rapid Golgi technique and the growth and branching of the dendritic arbors were quantified using the Sholl method. In addition, the density of dendritic spines was determined on the apical arbors of each population. In GR brains (n = 7) compared to controls (n = 7), there was a reduction in dendritic elongation (p < 0.005) and an alteration in the branch point distribution in CA1 basal arbors, and a reduction both in the outgrowth (p < 0.05) and branch point number (p < 0.05) of CA1 apical arbors. Dentate granule cells from GR brains also demonstrated reduced dendritic outgrowth (p < 0.05). There was an increase in dendritic spine density in both neuronal populations; this might be due either to altered synaptic pruning or as a compensatory mechanism for reduced dendritic length. These findings demonstrate that a chronic prenatal insult causes selective changes in the morphology of hippocampal cell dendrites and may lead to alterations in hippocampal function in the postnatal period.
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Affiliation(s)
- Sandra Dieni
- Department of Anatomy and Cell Biology, University of Melbourne, Parkville, 3010, Victoria, Australia.
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Huang LT, Holmes GL, Lai MC, Hung PL, Wang CL, Wang TJ, Yang CH, Liou CW, Yang SN. Maternal deprivation stress exacerbates cognitive deficits in immature rats with recurrent seizures. Epilepsia 2002; 43:1141-8. [PMID: 12366727 DOI: 10.1046/j.1528-1157.2002.14602.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Maternal deprivation is stressful for the neonate. The aim of this study was to investigate the short- and long-term effects of maternal separation on recurrent seizures in the developing brain. METHODS Rats were divided into four groups according to whether the rat pups were treated with maternal deprivation from postnatal day 2 (P2) to P9 or neonatal seizures induced by intraperitoneal (i.p.) injection of pentylenetetrazol (PTZ) from P10 to P14. Rats in the control group received saline i.p. injection from P10 to P14; rats in the isolation group underwent daily separation from their dams from P2 to P9; rats in the PTZ-treated group were subjected to PTZ-induced recurrent seizures from P10 to P14; rats in the isolation plus PTZ-treated group were subjected to maternal deprivation from P2 to P7 followed by serial seizures from P10 to P14. In addition, subsets of rats at P15 were killed and the brains assessed for acute neuronal degeneration. Visual-spatial memory test using the Morris water maze task was performed at P80. After testing, the hippocampus was evaluated for histologic lesions and cyclic adenosine monophosphate (cAMP)-responsive element-binding protein phosphorylation at serine-133 (pCREBSer-133), an important transcription factor underlying learning and memory. RESULTS All rats given PTZ developed recurrent seizures. After PTZ administration, rats with a history of maternal deprivation had more intense impairment than did rats with maternal deprivation and neonatal seizures than those without deprivation. Neuronal degeneration was most prominent in the rats exposed to maternal deprivation plus recurrent seizures. Rats receiving maternal deprivation or PTZ-induced recurrent seizures exhibited only spatial deficits, but no morphologic changes in the hippocampus. However, rats with maternal deprivation plus PTZ-induced recurrent seizures exhibited worse visual-spatial learning compared with rats with either isolation or PTZ-induced recurrent seizures alone. The levels of pCREBSer-133 may play a role in the decrease in the hippocampus from the rats subjected to maternal deprivation and/or PTZ-induced recurrent seizures, as compared with rats exposed to vehicle-control saline. These results indicate that repeated maternal deprivation can exacerbate long-term cognitive deficits resulting from neonatal seizures. In addition, impaired phosphorylation of CREBSer-133. CONCLUSIONS Repeated maternal deprivation stress has synergistic effects with recurrent seizures in inducing neurologic damage in the developing brain.
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Affiliation(s)
- Li-Tung Huang
- Department of Pediatrics and Neurology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan
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Bartesaghi R, Severi S. Effects of early environment on field CA3a pyramidal neuron morphology in the guinea-pig. Neuroscience 2002; 110:475-88. [PMID: 11906787 DOI: 10.1016/s0306-4522(01)00469-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There is evidence that early environmental conditions have profound effects on the morphology of the dentate granule cells. The aim of the present study was to obtain information about the effects of early environment on neuron morphology in the hippocampal field CA3, a structure closely linked to the dentate gyrus. The dendritic trees and the somata of field CA3a pyramidal neurons were quantified in Golgi-stained brains of guinea-pigs of both sexes raised in either a social or an isolated environment. Two pyramidal neuron types were found in CA3a, characterized by either a long or a short shaft. Environment affected the apical tree of the long-shaft neurons only in males and that of the short-shaft neurons in both sexes. In isolated males the long-shaft neurons had a decrease in the number of dendritic intersections (62-82%), branching points (76%) and length (71%) in the middle third of the apical tree. The short-shaft neurons had a decrease in the number of intersections at two distal levels only in both isolated males (26, 83%) and females (77, 82%). The shaft spine density was affected by environment in the long-shaft neurons of males only, with a density increase (110%) in isolated males. In both sexes the basal tree of only the long-shaft neurons was affected by environment. Isolated males had a decrease in the number of dendritic intersections (65-88%), primary dendrites (80%) and dendritic length (88%) and isolated females had a decrease in the number of intersections (51-89%), branching points (77%) and dendritic length (85%). The soma major axis of only the long-shaft neurons was affected by environment with a reduction in isolated males (90%) but an increase in isolated females (111%). These results demonstrate dendritic atrophy of CA3a pyramidal neurons following early isolation and a different reactivity to environment of the two CA3a pyramidal neuron types, their apical and basal trees and the two sexes. The dendritic atrophy of CA3a neurons caused by isolation is likely to be associated with an impairment in the physiology of the hippocampal formation and in the forms of memory in which the hippocampal formation plays a major role.
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Affiliation(s)
- R Bartesaghi
- Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza di Porta S. Donato 2, I-40127, Bologna, Italy.
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