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Puhahn-Schmeiser B, Kleemann T, Jabbarli R, Bock HH, Beck J, Freiman TM. Granule cell dispersion in two mouse models of temporal lobe epilepsy and reeler mice is associated with changes in dendritic orientation and spine distribution. Hippocampus 2022; 32:517-528. [PMID: 35621370 DOI: 10.1002/hipo.23447] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 04/05/2022] [Accepted: 04/11/2022] [Indexed: 11/06/2022]
Abstract
Temporal lobe epilepsy is characterized by hippocampal neuronal death in CA1 and hilus. Dentate gyrus granule cells survive but show dispersion of the compact granule cell layer. This is associated with decrease of the glycoprotein Reelin, which regulates neuron migration and dendrite outgrow. Reelin-deficient (reeler) mice show no layering, their granule cells are dispersed throughout the dentate gyrus. We studied granule cell dendritic orientation and distribution of postsynaptic spines in reeler mice and two mouse models of temporal lobe epilepsy, namely the p35 knockout mice, which show Reelin-independent neuronal migration defects, and mice with unilateral intrahippocampal kainate injection. Granule cells were Golgi-stained and analyzed, using a computerized camera lucida system. Granule cells in naive controls exhibited a vertically oriented dendritic arbor with a small bifurcation angle if positioned proximal to the hilus and a wider dendritic bifurcation angle, if positioned distally. P35 knockout- and kainate-injected mice showed a dispersed granule cell layer, granule cells showed basal dendrites with wider bifurcation angles, which lost position-specific differences. Reeler mice lacked dendritic orientation. P35 knockout- and kainate-injected mice showed increased dendritic spine density in the granule cell layer. Molecular layer dendrites showed a reduced spine density in kainate-injected mice only, whereas in p35 knockouts no reduced spine density was seen. Reeler mice showed a homogenous high spine density. We hypothesize that granule cells migrate in temporal lobe epilepsy, develop new dendrites which show a spread of the dendritic tree, create new spines in areas proximal to mossy fiber sprouting, which is present in p35 knockout- and kainate-injected mice and loose spines on distal dendrites if mossy cell death is present, as it was in kainate-injected mice only. These results are in accordance with findings in epilepsy patients.
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Affiliation(s)
- Barbara Puhahn-Schmeiser
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Freiburg, Freiburg, Germany
| | - Tobias Kleemann
- Department of Gastroenterology and Rheumatology, Carl-Thiem-Hospital, Cottbus, Germany
| | - Ramazan Jabbarli
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Duisburg-Essen, Essen, Germany
| | - Hans H Bock
- Faculty of Medicine, Department of Gastroenterology, Hepatology and Infectiology, Medical Center, University of Duesseldorf, Duesseldorf, Germany
| | - Jürgen Beck
- Faculty of Medicine, Department of Neurosurgery, Medical Center, University of Freiburg, Freiburg, Germany
| | - Thomas M Freiman
- Department of Neurosurgery, University Medical Center Rostock, Rostock, Germany
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Sloviter RS, Lømo T. Updating the lamellar hypothesis of hippocampal organization. Front Neural Circuits 2012; 6:102. [PMID: 23233836 PMCID: PMC3517983 DOI: 10.3389/fncir.2012.00102] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 11/21/2012] [Indexed: 11/13/2022] Open
Abstract
Andersen et al. (1971) proposed that excitatory activity in the entorhinal cortex propagates topographically to the dentate gyrus, and on through a "trisynaptic circuit" lying within transverse hippocampal "slices" or "lamellae." In this way, a relatively simple structure might mediate complex functions in a manner analogous to the way independent piano keys can produce a nearly infinite variety of unique outputs. The lamellar hypothesis derives primary support from the "lamellar" distribution of dentate granule cell axons (the mossy fibers), which innervate dentate hilar neurons and area CA3 pyramidal cells and interneurons within the confines of a thin transverse hippocampal segment. Following the initial formulation of the lamellar hypothesis, anatomical studies revealed that unlike granule cells, hilar mossy cells, CA3 pyramidal cells, and Layer II entorhinal cells all form axonal projections that are more divergent along the longitudinal axis than the clearly "lamellar" mossy fiber pathway. The existence of pathways with "translamellar" distribution patterns has been interpreted, incorrectly in our view, as justifying outright rejection of the lamellar hypothesis (Amaral and Witter, 1989). We suggest that the functional implications of longitudinally projecting axons depend not on whether they exist, but on what they do. The observation that focal granule cell layer discharges normally inhibit, rather than excite, distant granule cells suggests that longitudinal axons in the dentate gyrus may mediate "lateral" inhibition and define lamellar function, rather than undermine it. In this review, we attempt a reconsideration of the evidence that most directly impacts the physiological concept of hippocampal lamellar organization.
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Affiliation(s)
- Robert S Sloviter
- Department of Neurobiology, Morehouse School of Medicine Atlanta, GA, USA
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Asrar S, Kaneko K, Takao K, Negandhi J, Matsui M, Shibasaki K, Miyakawa T, Harrison RV, Jia Z, Salter MW, Tominaga M, Fukumi-Tominaga T. DIP/WISH deficiency enhances synaptic function and performance in the Barnes maze. Mol Brain 2011; 4:39. [PMID: 22018352 PMCID: PMC3208581 DOI: 10.1186/1756-6606-4-39] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 10/21/2011] [Indexed: 01/20/2023] Open
Abstract
Background DIP (diaphanous interacting protein)/WISH (WASP interacting SH3 protein) is a protein involved in cytoskeletal signaling which regulates actin cytoskeleton dynamics and/or microtubules mainly through the activity of Rho-related proteins. Although it is well established that: 1) spine-head volumes change dynamically and reflect the strength of the synapse accompanying long-term functional plasticity of glutamatergic synaptic transmission and 2) actin organization is critically involved in spine formation, the involvement of DIP/WISH in these processes is unknown. Results We found that DIP/WISH-deficient hippocampal CA1 neurons exhibit enhanced long-term potentiation via modulation of both pre- and post-synaptic events. Consistent with these electrophysiological findings, DIP/WISH-deficient mice, particularly at a relatively young age, found the escape hole more rapidly in the Barnes maze test. Conclusions We conclude that DIP/WISH deletion improves performance in the Barnes maze test in mice probably through increased hippocampal long-term potentiation.
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Affiliation(s)
- Suhail Asrar
- Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), Japan
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Volz F, Bock HH, Gierthmuehlen M, Zentner J, Haas CA, Freiman TM. Stereologic estimation of hippocampal GluR2/3- and calretinin-immunoreactive hilar neurons (presumptive mossy cells) in two mouse models of temporal lobe epilepsy. Epilepsia 2011; 52:1579-89. [PMID: 21635231 DOI: 10.1111/j.1528-1167.2011.03086.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Hippocampal mossy cells receive dense innervation from dentate granule cells and, in turn, mossy cells innervate both granule cells and interneurons. Mossy cell loss is thought to trigger granule cell mossy fiber sprouting, which may affect granule cell excitability. The aim of this study was to quantify mossy cell loss in two animal models of temporal lobe epilepsy, and determine whether there exists a relationship between mossy cell loss, mossy fiber sprouting, and granule cell dispersion. METHODS Representative hippocampal sections from p35 knockout mice and mice with unilateral intrahippocampal kainate injection were immunolabeled for GluR2/3, two subunits of the amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor and calretinin to identify mossy cells. Mossy fibers were immunostained against synaptoporin. KEY FINDINGS p35 Knockout mice showed no hilar cell death, but moderate mossy fiber sprouting and granule cell dispersion. In the kainate-injected hippocampus, there was an 80% and 85% reduction of GluR2/3- and GluR2/3/calretinin-positive hilar neurons, respectively, and dense mossy fiber sprouting and significant granule cell dispersion. In the contralateral hippocampus there was a 52% loss of GluR2/3-, but only a 20% loss of GluR2/3-calretinin-immunoreactive presumptive mossy cells, and granule cell dispersion; no mossy fiber sprouting was observed. SIGNIFICANCE These results indicate a probable lack of causality between mossy cell death and mossy fiber sprouting.
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Affiliation(s)
- Florian Volz
- Department of Neurosurgery, University Medical Center, Albert-Ludwigs-University, Freiburg, Germany
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Freiman TM, Eismann-Schweimler J, Frotscher M. Granule cell dispersion in temporal lobe epilepsy is associated with changes in dendritic orientation and spine distribution. Exp Neurol 2011; 229:332-8. [DOI: 10.1016/j.expneurol.2011.02.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 02/16/2011] [Accepted: 02/20/2011] [Indexed: 01/16/2023]
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Norkute A, Hieble A, Braun A, Johann S, Clarner T, Baumgartner W, Beyer C, Kipp M. Cuprizone treatment induces demyelination and astrocytosis in the mouse hippocampus. J Neurosci Res 2009; 87:1343-55. [PMID: 19021291 DOI: 10.1002/jnr.21946] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Memory impairment is outstanding within the spectrum of cognitive deficits in multiple sclerosis (MS) patients. Demyelination has been reported in the hippocampus formation of MS patients. The degree of hippocampus lesions in MS strongly correlates with progression of cognitive dysfunction. Because no appropriate animal model for the study of hippocampus demyelination has been established, we used the cuprizone mouse model to investigated demyelination in young adult and aged mice. The myelin status was analyzed by classical histological staining, immunocytochemistry for proteolipoprotein, and electron microscopy. Oligodendrocyte, astroglial, and microglia markers were studied. Cuprizone intoxication induced an almost complete demyelination of distinct hippocampus subregions to a similar extent in young adult and aged male mice. Demyelination was pronounced in a subset of white and gray matter areas, i.e., the stratum lacunosum moleculare containing the perforant path, medial alveus, stratum pyramidale in the cornu ammonis 2/3 region, and hilus region. Besides demyelination, affected areas displayed hypertrophic and hyperplastic astrocytosis. No significant effect on microglia invasion was detected at any investigated time point (0, 3, 5, and 7 weeks). We conclude that cuprizone-induced demyelination provides an adequate animal model to investigate appropriate therapy strategies for the prevention of hippocampus demyelination.
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Affiliation(s)
- Akvile Norkute
- Institute of Neuroanatomy, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
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Frotscher M, Zhao S, Förster E. Development of cell and fiber layers in the dentate gyrus. PROGRESS IN BRAIN RESEARCH 2007; 163:133-42. [PMID: 17765715 DOI: 10.1016/s0079-6123(07)63007-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
This chapter deals with the laminated organization of the dentate gyrus, particularly with the molecular signals controlling its development. First, sites of granule cell generation, their modes and routes of migration are described. This is followed by an analysis of the molecular determinants governing the formation of a tightly packed granule cell layer that is normal in rodents and primates. Reelin, a protein of the extracellular matrix, plays an important role for the proper migration and lamination of the granule cells during development and for the maintenance of a laminated dentate gyrus in adulthood. Granule cell positioning is crucial for the laminated termination of commissural/associational fibers to the dentate gyrus, suggesting that the granule cells carry positional signals for these fibers. In contrast, not signals of the target cells but molecules of the extracellular matrix, such as hyaluronan, underlie the layer-specific termination of fibers from the entorhinal cortex. The molecular determinants controlling axonal pathfinding and target recognition of the profusely terminating cholinergic and GABAergic subcortical afferents still need to be elucidated.
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Affiliation(s)
- Michael Frotscher
- Institute of Anatomy and Cell Biology, University of Freiburg, Albertstr. 17, D-79104 Freiburg, Germany.
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Ribak CE, Shapiro LA. Ultrastructure and synaptic connectivity of cell types in the adult rat dentate gyrus. PROGRESS IN BRAIN RESEARCH 2007; 163:155-66. [PMID: 17765717 DOI: 10.1016/s0079-6123(07)63009-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The rat hippocampal dentate gyrus is an extensively studied structural component of the limbic system. It is the first station in the classical tri-synaptic circuit of the hippocampus in that its major input arises from the entorhinal cortex via the perforant pathway. The second part of this circuit arises from the projection cells of the dentate gyrus, the granule cells, which send their axons to the pyramidal cells of CA3. Within the dentate gyrus, there also is an extensive inhibitory network of cells that are involved in synchronizing the rhythmic firing of the granule cells. This chapter provides a review of the ultrastructural features and synaptic connectivity of both projection cells and local circuit neurons in the dentate gyrus.
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Affiliation(s)
- Charles E Ribak
- Department of Anatomy & Neurobiology, University of California at Irvine, Irvine, CA 92697-1275, USA.
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La técnica de impregnación argéntica de Golgi. Conmemoración del centenario del premio nobel de Medicina (1906) compartido por Camillo Golgi y Santiago Ramón y Cajal. BIOMEDICA 2006. [DOI: 10.7705/biomedica.v26i4.315] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Fahrner A, Kann G, Flubacher A, Heinrich C, Freiman TM, Zentner J, Frotscher M, Haas CA. Granule cell dispersion is not accompanied by enhanced neurogenesis in temporal lobe epilepsy patients. Exp Neurol 2006; 203:320-32. [PMID: 17049346 DOI: 10.1016/j.expneurol.2006.08.023] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 08/07/2006] [Accepted: 08/15/2006] [Indexed: 10/24/2022]
Abstract
Granule cell dispersion (GCD) in the dentate gyrus is a frequent feature of Ammon's horn sclerosis (AHS) which is often associated with temporal lobe epilepsy (TLE). It has been hypothesized that GCD may be caused by an abnormal migration of newly born granule cells. To test this hypothesis, we used markers of proliferation and neurogenesis and immunocytochemical methods as well as quantitative Western blot and real-time RT-PCR analyses in surgically resected hippocampi from TLE patients and controls. Below the age of 1 year, Ki-67-immunopositive nuclei were detected in the subgranular zone of the dentate gyrus, but not in the dentate of TLE patients independent of age. The expression of the proliferation marker minichromosome maintenance protein 2 (mcm2) and of doublecortin (DCX) decreased significantly with age in controls and in TLE patients, but the expression of both proteins was independent of the degree of AHS and GCD. Quantitative real-time RT-PCR confirmed these findings at the level of gene expression. In contrast, immunocytochemistry for glial fibrillary acidic protein (GFAP) and vimentin as well as Golgi staining revealed a radially aligned glial network in the region of GCD. GFAP-positive fiber length significantly increased with the severity of GCD. These results indicate that epileptic activity does not stimulate neurogenesis in the human dentate gyrus and that GCD probably does not result from a malpositioning of newly generated granule cells, but rather from an abnormal migration of mature granule cells along a radial glial scaffold.
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Affiliation(s)
- Alexander Fahrner
- Experimental Epilepsy Group, Neurocenter, University of Freiburg, Breisacher Strasse 64, D-79106 Freiburg, Germany
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Schmitt O, Pakura M, Aach T, Hömke L, Böhme M, Bock S, Preusse S. Analysis of nerve fibers and their distribution in histologic sections of the human brain. Microsc Res Tech 2004; 63:220-43. [PMID: 14988920 DOI: 10.1002/jemt.20033] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The field of quantitative analysis and subsequent mapping of the cerebral cortex has developed rapidly. New powerful tools have been applied to investigate large regions of complex folded gyrencephalic cortices in order to detect structural transition regions that might partition different cortical fields of disjunct neuronal functions. We have developed a new mapping approach based on axoarchitectonics, a method of cortical visualization that previously has been used only indirectly with regard to myeloarchitectonics. Myeloarchitectonic visualization has the disadvantage of producing strong agglomerative effects of closely neighbored nerve fibers. Therefore, single and neurofunctional-relevant parameters such as axonal branchings, axon areas, and axon numbers have not been determinable with satisfying precision. As a result, different staining techniques had to be explored in order to achieve a suitable histologic staining for axon visualization. The best results were obtained after modifying the Naoumenko-Feigin staining for axons. From these contrast-rich stained histologic sections, videomicroscopic digital image tiles were generated and analyzed using a new fiber analysis framework. Finally, the analysis of histologic images provided topologic ordered parameters of axons that were transferred into parameter maps. The axon parameter maps were analyzed further via a recently developed traverse generating algorithm that calculated test lines oriented perpendicular to the cortical surface and white matter border. The gray value coded parameters of the parameter maps were then transferred into profile arrays. These profile arrays were statistically analyzed by a reliable excess mass approach we recently developed. We found that specific axonal parameters are preferentially distributed throughout granular and agranular types of cortex. Furthermore, our new procedure detected transition regions originally defined by changes of cytoarchitectonic layering. Statistically significant inhomogeneities of the distribution of certain axon quantities were shown to indicate a subparcellation of areas 4 and 6. The quantification techniques established here for the analysis of spatial axon distributions within larger regions of the cerebral cortex are suitable to detect inhomogeneities of laminar axon patterns. Hence, these techniques can be recommended for systematic and observer-supported cortical area mapping and parcellation studies.
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Affiliation(s)
- O Schmitt
- Institute of Anatomy, University of Rostock, D-18055 Rostock, Germany.
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Deller T, Korte M, Chabanis S, Drakew A, Schwegler H, Stefani GG, Zuniga A, Schwarz K, Bonhoeffer T, Zeller R, Frotscher M, Mundel P. Synaptopodin-deficient mice lack a spine apparatus and show deficits in synaptic plasticity. Proc Natl Acad Sci U S A 2003; 100:10494-9. [PMID: 12928494 PMCID: PMC193589 DOI: 10.1073/pnas.1832384100] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2003] [Indexed: 11/18/2022] Open
Abstract
The spine apparatus is a cellular organelle that is present in many dendritic spines of excitatory neurons in the mammalian forebrain. Despite its discovery >40 years ago, the function of the spine apparatus is still unknown although calcium buffering functions as well as roles in synaptic plasticity have been proposed. We have recently shown that the 100-kDa protein synaptopodin is associated with the spine apparatus. Here, we now report that mice homozygous for a targeted deletion of the synaptopodin gene completely lack spine apparatuses. Interestingly, this absence of the spine apparatus is accompanied by a reduction in hippocampal long-term potentiation (LTP) in the CA1 region of the hippocampus and by an impairment of spatial learning in the radial arm maze test. This genetic analysis points to a role of the spine apparatus in synaptic plasticity.
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Affiliation(s)
- Thomas Deller
- Institute of Anatomy, University of Freiburg, P.O. Box 111, D-79001 Freiburg, Germany
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Abstract
Ramon y Cajal proclaimed in 1928 that "once development was ended, the founts of growth and regeneration of the axons and dendrites dried up irrevocably. In the adult centers the nerve paths are something fixed, ended and immutable. Everything must die, nothing may be regenerated. It is for the science of the future to change, if possible, this harsh decree." (Ramon y Cajal, 1928). In large part, despite the extensive knowledge gained since then, the latter directive has not yet been achieved by 'modern' science. Although we know now that Ramon y Cajal's observation on CNS plasticity is largely true (for lower brain and primary cortical structures), there are mechanisms for recovery from CNS injury. These mechanisms, however, may contribute to the vulnerability to neurodegenerative disease. They may also be exploited therapeutically to help alleviate the suffering from neurodegenerative conditions.
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Affiliation(s)
- Bruce Teter
- Department of Medicine, University of California Los Angeles, California and Veteran's Affairs-Greater Los Angeles Healthcare System, Sepulveda, California 91343, USA
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Förster E, Tielsch A, Saum B, Weiss KH, Johanssen C, Graus-Porta D, Müller U, Frotscher M. Reelin, Disabled 1, and beta 1 integrins are required for the formation of the radial glial scaffold in the hippocampus. Proc Natl Acad Sci U S A 2002; 99:13178-83. [PMID: 12244214 PMCID: PMC130606 DOI: 10.1073/pnas.202035899] [Citation(s) in RCA: 212] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2002] [Indexed: 11/18/2022] Open
Abstract
The extracellular matrix molecule Reelin is required for the correct positioning of neurons during the development of the forebrain. However, the mechanism of Reelin action on neuronal migration is poorly understood. Reelin is assumed to act on neurons directly, but it may also affect the differentiation of glial cells necessary for neuronal migration. Here we show that a regular glial scaffold fails to form in vivo in the dentate gyrus of mice deficient of Reelin or Disabled 1, a neuronal adaptor protein in the Reelin signaling pathway. A subset of these defects is observed in mice that lack beta(1)-class integrins, known to bind Reelin. Moreover, recombinant Reelin induced branching of glial processes in vitro. Our data suggest that Reelin affects glial differentiation via Disabled 1 and beta(1)-class integrin-dependent signaling pathways.
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Affiliation(s)
- Eckart Förster
- Anatomisches Institut, Universität Freiburg, P.O. Box 111, D-79001 Freiburg, Germany.
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Drakew A, Deller T, Heimrich B, Gebhardt C, Del Turco D, Tielsch A, Förster E, Herz J, Frotscher M. Dentate granule cells in reeler mutants and VLDLR and ApoER2 knockout mice. Exp Neurol 2002; 176:12-24. [PMID: 12093079 DOI: 10.1006/exnr.2002.7918] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have studied the organization and cellular differentiation of dentate granule cells and their axons, the mossy fibers, in reeler mutant mice lacking reelin and in mutants lacking the reelin receptors very low density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2). We show that granule cells in reeler mice do not form a densely packed granular layer, but are loosely distributed throughout the hilar region. Immunolabeling for calbindin and calretinin revealed that the sharp border between dentate granule cells and hilar mossy cells is completely lost in reeler mice. ApoER2/VLDLR double-knockout mice copy the reeler phenotype. Mice deficient only in VLDLR showed minor alterations of dentate organization; migration defects were more prominent in ApoER2 knockout mice. Tracing of the mossy fibers with Phaseolus vulgaris leukoagglutinin and calbindin immunolabeling revealed an irregular broad projection in reeler mice and ApoER2/VLDLR double knockouts, likely caused by the irregular wide distribution of granule cell somata. Mutants lacking only one of the lipoprotein receptors showed only minor changes in the mossy fiber projection. In all mutants, mossy fibers respected the CA3-CA1 border. Retrograde labeling with DiI showed that malpositioned granule cells also projected as normal to the CA3 region. These results indicate that ( 1 ) reelin signaling via ApoER2 and VLDLR is required for the normal positioning of dentate granule cells and (2) the reelin signaling pathway is not involved in pathfinding and target recognition of granule cell axons.
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Affiliation(s)
- Alexander Drakew
- Institute of Anatomy, University of Freiburg, Albertstrasse 17, Freiburg, D-79104, Germany
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Drakew A, Frotscher M, Heimrich B. Blockade of neuronal activity alters spine maturation of dentate granule cells but not their dendritic arborization. Neuroscience 1999; 94:767-74. [PMID: 10579567 DOI: 10.1016/s0306-4522(99)00378-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Organotypic co-cultures of the entorhinal cortex and hippocampus were examined to determine the role of the entorhinal fibers in the dendritic development and formation of spines of dentate granule cells. Quantitative analysis of Golgi-impregnated granule cells in single hippocampal cultures and co-cultures with the entorhinal cortex revealed that the presence of entorhinal fibers promoted the elongation and differentiation of the target granule cell dendrites. This was accompanied by an increase in the total number of spines. The contribution of neuronal activity to this afferent-mediated dendritic development was tested by chronic application of the sodium channel blocker tetrodotoxin for 20 days in vitro. Tracing with biocytin showed that the formation of the entorhinohippocampal pathway was unaffected by the blockade of neuronal activity. The dendritic arbor of cultured granule cells and the number of dendritic spines did not differ between tetrodotoxin-treated slices and untreated controls. However, there was a significant increase in the relative number of filiform spines on granule cell dendrites in tetrodotoxin-treated co-cultures. Such filiform spines are a characteristic feature of immature neurons. These results suggest the cooperation of two mechanisms in the dendritic development of dentate granule cells: the specific afferent-mediated dendritic arborization and the activity-dependent maturation of spines.
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Affiliation(s)
- A Drakew
- Institute of Anatomy, University of Freiburg, Germany
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Teter B, Xu PT, Gilbert JR, Roses AD, Galasko D, Cole GM. Human apolipoprotein E isoform-specific differences in neuronal sprouting in organotypic hippocampal culture. J Neurochem 1999; 73:2613-6. [PMID: 10582625 DOI: 10.1046/j.1471-4159.1999.0732613.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The apolipoprotein E (ApoE) epsilon4 allele is a major risk factor for neurodegenerative conditions, including Alzheimer's disease. A role for ApoE is implicated in regeneration of synaptic circuitry after neural injury. In the in vitro mouse organotypic hippocampal slice culture system, we previously showed that cultures derived from ApoE-knockout mice are defective in mossy fiber sprouting into the dentate gyrus molecular layer. This sprouting defect was rescued in cultures from transgenic mice expressing ApoE3 under the control of the human promoter and in ApoE-knockout cultures treated with ApoE3-conditioned media. Although the ApoE3 transgene fully restored sprouting, ApoE4 restored sprouting to only 58% of ApoE3 levels. These data indicate that ApoE isoform-specific effects on neuroregeneration may contribute to its genetic risk for Alzheimer's disease.
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Affiliation(s)
- B Teter
- Veterans Administration Medical Center, Sepulveda, California 91343, USA
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Teter B, Harris-White ME, Frautschy SA, Cole GM. Role of apolipoprotein E and estrogen in mossy fiber sprouting in hippocampal slice cultures. Neuroscience 1999; 91:1009-16. [PMID: 10391478 DOI: 10.1016/s0306-4522(98)00630-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A role for apolipoprotein E is implicated in regeneration of synaptic circuitry after neural injury. The in vitro mouse organotypic hippocampal slice culture system shows Timm's stained mossy fiber sprouting into the dentate gyrus molecular layer in response to deafferentation of the entorhinal cortex. We show that cultures derived from apolipoprotein E knockout mice are defective in this sprouting response; specifically, they show no sprouting in the dorsal region of the dentate gyrus, yet retain sprouting in the ventral region. Dorsal but not ventral sprouting in cultures from C57B1/6J mice is increased 75% by treatment with 100 pM 17beta-estradiol; this response is blocked by both progesterone and tamoxifen. These results show that neuronal sprouting is increased by estrogen in the same region where sprouting is dependent on apolipoprotein E. Sprouting may be stimulated by estrogen through its up-regulation of apolipoprotein E expression leading to increased recycling of membrane lipids for use by sprouting neurons. Estrogen and apolipoprotein E may therefore interact in their modulation of both Alzheimer's disease risk and recovery from CNS injury.
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Affiliation(s)
- B Teter
- Greater Los Angeles Veteran's Healthcare System, Sepulveda, and Department of Medicine, University of California, Los Angeles, 91343, USA
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19
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Zamanillo D, Sprengel R, Hvalby O, Jensen V, Burnashev N, Rozov A, Kaiser KM, Köster HJ, Borchardt T, Worley P, Lübke J, Frotscher M, Kelly PH, Sommer B, Andersen P, Seeburg PH, Sakmann B. Importance of AMPA receptors for hippocampal synaptic plasticity but not for spatial learning. Science 1999; 284:1805-11. [PMID: 10364547 DOI: 10.1126/science.284.5421.1805] [Citation(s) in RCA: 612] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Gene-targeted mice lacking the L-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor subunit GluR-A exhibited normal development, life expectancy, and fine structure of neuronal dendrites and synapses. In hippocampal CA1 pyramidal neurons, GluR-A-/- mice showed a reduction in functional AMPA receptors, with the remaining receptors preferentially targeted to synapses. Thus, the CA1 soma-patch currents were strongly reduced, but glutamatergic synaptic currents were unaltered; and evoked dendritic and spinous Ca2+ transients, Ca2+-dependent gene activation, and hippocampal field potentials were as in the wild type. In adult GluR-A-/- mice, associative long-term potentiation (LTP) was absent in CA3 to CA1 synapses, but spatial learning in the water maze was not impaired. The results suggest that CA1 hippocampal LTP is controlled by the number or subunit composition of AMPA receptors and show a dichotomy between LTP in CA1 and acquisition of spatial memory.
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Affiliation(s)
- D Zamanillo
- Department of Molecular Neuroscience, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
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20
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Zarei MM, Radcliffe KA, Chen D, Patrick JW, Dani JA. Distributions of nicotinic acetylcholine receptor alpha7 and beta2 subunits on cultured hippocampal neurons. Neuroscience 1999; 88:755-64. [PMID: 10363815 DOI: 10.1016/s0306-4522(98)00246-2] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The hippocampus receives cholinergic afferents and expresses neuronal nicotinic acetylcholine receptors. In particular, the alpha7 and beta2 nicotinic subunits are highly expressed in the hippocampus. There has been controversy about the location, distribution and roles of neuronal nicotinic acetylcholine receptors [Role L. W. and Berg D. K. (1996) Neuron 16, 1077-1085; Wonnacott S. (1997) Trends Neurosci. 20, 92-98]. Using immunocytochemistry and patch-clamp techniques, we examined the density and distribution of nicotinic receptors on rat hippocampal neurons in primary tissue culture. The density and distribution of alpha7 subunits change with days in culture. Before 10 days in culture, alpha7 expression, monitored immunocytochemically, is low and nicotinic currents are small or absent. In older cultures, about two-thirds of the neurons express nicotinic currents, and alpha7 appears in small patches on the soma and out along the neuronal processes. These patches of alpha7 subunits on the surface of the neuronal processes often co-localize with the presynaptic marker, synaptotagmin. The other most common nicotinic subunit, beta2, stays confined mainly to the soma and proximal processes, and beta2 is distributed more uniformly and is not specifically localized at presynaptic areas. The two subunits, alpha7 and beta2, have different expression patterns on the surface of the cultured hippocampal neurons. Taken together with previous physiological studies, the results indicate that alpha7 subunits can be found at presynaptic terminals, and at these locations, these calcium-permeable channels may influence transmitter release.
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Affiliation(s)
- M M Zarei
- Division of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
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21
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Abstract
Recent immunoelectron microscopic studies have revealed a low frequency of synaptic membrane differentiations on ACh (ChAT-immunostained) axon terminals (boutons or varicosities) in adult rat cerebral cortex, hippocampus and neostriatum, suggesting that, besides synaptic transmission, diffuse transmission by ACh prevails in many regions of the CNS. Cytological analysis of the immediate micro-environment of these ACh terminals, as well as currently available immunocytochemical data on the cellular and subcellular distribution of ACh receptors, is congruent with this view. At least in brain regions densely innervated by ACh neurons, a further aspect of the diffuse transmission paradigm is envisaged: the existence of an ambient level of ACh in the extracellular space, to which all tissue elements would be permanently exposed. Recent experimental data on the various molecular forms of AChE and their presumptive role at the neuromuscular junction support this hypothesis. As in the peripheral nervous system, degradation of ACh by the prevalent G4 form of AChE in the CNS would primarily serve to keep the extrasynaptic, ambient level of ACh within physiological limits, rather than totally eliminate ACh from synaptic clefts. Long-lasting and widespread electrophysiological effects imputable to ACh in the CNS might be explained in this manner. The notions of diffuse transmission and of an ambient level of ACh in the CNS could also be of clinical relevance, in accounting for the production and nature of certain cholinergic deficits and the efficacy of substitution therapies.
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Affiliation(s)
- L Descarries
- Département de physiologie, Faculté de médecine, Université de Montréal, QC, Canada.
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22
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Albuquerque EX, Pereira EF, Alkondon M, Schrattenholz A, Maelicke A. Nicotinic acetylcholine receptors on hippocampal neurons: distribution on the neuronal surface and modulation of receptor activity. J Recept Signal Transduct Res 1997; 17:243-66. [PMID: 9029494 DOI: 10.3109/10799899709036607] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The recent development of a technique that uses infrared microscopy for the visualization of well-defined areas on the surface of neurons, and a computerized system of micromanipulators led to the discovery that functional nicotinic acetylcholine receptors (nAChRs) are expressed at higher density on the dendrites than on the soma of rat hippocampal neurons. The finding that the expression of alpha-bungarotoxin-sensitive, alpha 7-bearing, nAChRs and dihydro-beta-erythroidine-sensitive, alpha 4 beta 2 nAChRs tends to increase along the dendritic length suggests that these receptors may be highly involved in the integration of synaptic functions in hippocampal neurons. The present report also discusses the finding that ligands such as the anticholinesterase galanthamine can modulate the nAChR activity by binding to a novel receptor site, and that 5-hydroxytryptamine (5-HT) may serve as an endogenous ligand for this site. The ability of 5-HT to modulate the nAChR function in vivo supports the concept that the overall CNS function is determined not only by the neuronal network established by the neuronal wiring, but also by a chemical network established by the ability of a single substance to act as the primary neurotransmitter in one system and as a co-transmitter in another system.
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Affiliation(s)
- E X Albuquerque
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201, USA
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23
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Martínez A, Lübke J, Del Río JA, Soriano E, Frotscher M. Regional variability and postsynaptic targets of chandelier cells in the hippocampal formation of the rat. J Comp Neurol 1996; 376:28-44. [PMID: 8946282 DOI: 10.1002/(sici)1096-9861(19961202)376:1<28::aid-cne2>3.0.co;2-q] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chandelier cells are specialized cortical GABAergic neurons that establish synaptic contacts exclusively with the axon initial segments of principal neurons. They are found in all regions of the hippocampal formation. Here we describe their morphological features in the hilus and in regions CA1 and CA3 by using Golgi/electron microscopy. Attempts were also made to identify the target neurons of chandelier cells in the hilus and entorhinal cortex. Golgi-impregnated chandelier cells display a complex axonal arbor in CA1, with many collaterals forming strings of boutons. The axon plexuses of such cells are less developed in CA3, whereas those in the hilus cover the entire region, although single collaterals are rather simple, with only a few boutons. The dendrites of chandelier cells in CA1 and CA3 have an orientation similar to that of pyramidal cell dendrites and are thus likely to be activated by the same afferent fiber systems. The hilar chandelier cells do not give rise to dendrites invading the molecular layer. Thus, these cells may not receive a dense input from the entorhinal cortex but may be driven by the abundant mossy fiber collaterals in the hilar region. In the CA1 and CA3 regions, the axons of chandelier cells contact the axon initial segments of pyramidal cells. In the hilar region, gold-toned boutons were found to impinge on the initial segments of neurons displaying characteristics of mossy cells. This notion was substantiated by electron microscopic analysis of mossy cells identified by intracellular injection of Lucifer yellow. Those cells regularly showed numerous symmetric synapses on their axon initial segments. Entorhinohippocampal projection cells, identified by injection of horseradish peroxidase into the hippocampus, were found to be preferential targets of chandelier cells in the entorhinal cortex. Our data point to regional variations in chandelier cell morphology and connectivity and indicate that chandelier cells are a principal component of inhibitory mechanisms in all stations of the main excitatory pathway of the hippocampal formation.
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Affiliation(s)
- A Martínez
- Department of Animal and Plant Cell Biology, Faculty of Biology, University of Barcelona, Spain
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24
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Albuquerque EX, Pereira EF, Bonfante-Cabarcas R, Marchioro M, Matsubayashi H, Alkondon M, Maelicke A. Nicotinic acetylcholine receptors on hippocampal neurons: cell compartment-specific expression and modulatory control of channel activity. PROGRESS IN BRAIN RESEARCH 1996; 109:111-24. [PMID: 9009698 DOI: 10.1016/s0079-6123(08)62093-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- E X Albuquerque
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201, USA
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25
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Frotscher M, Zafirov S, Heimrich B. Development of identified neuronal types and of specific synaptic connections in slice cultures of rat hippocampus. Prog Neurobiol 1995; 45:vii-xxviii. [PMID: 7624484 DOI: 10.1016/0301-0082(95)90872-h] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- M Frotscher
- Institute of Anatomy, University of Freiburg, Germany
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26
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Frotscher M, Zafirov S, Heimrich B. Development of identified neuronal types and of specific synaptic connections in slice cultures of rat hippocampus. Prog Neurobiol 1995; 45:143-64. [PMID: 7598766 DOI: 10.1016/0301-0082(94)00040-o] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- M Frotscher
- Institute of Anatomy, University of Freiburg, Germany
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27
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Linke R, Soriano E, Frotscher M. Transient dendritic appendages on differentiating septohippocampal neurons are not the sites of synaptogenesis. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1994; 83:67-78. [PMID: 7697872 DOI: 10.1016/0165-3806(94)90180-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The factors which determine the final shape and synaptic connections of a neuronal phenotype are largely unknown. In adult animals, a large number of projection neurons, e.g. cortical pyramidal neurons, bear spines which, in the case of pyramidal cells, are postsynaptic elements of mainly asymmetric synapses. In contrast, mature septohippocampal neurons do not bear spines. During maturation, however, septohippocampal projection neurons develop a variety of dendritic appendages. Because the appearance of these processes falls into the period of synaptogenesis, it has been hypothesized that these transient appendages may be the site of synaptogenesis. Here we have investigated whether these transient dendritic appendages are the site of initial synaptic contacts of septohippocampal neurons. Septohippocampal projection neurons in late embryonic and early postnatal rats were identified by retrograde tracing with the carbocyanine dye DiI or biocytin. Subsequently, selected cells were processed for electron microscopy. Serial thin sections through identified dendritic appendages did not reveal synaptic contacts with presynaptic boutons but immature to mature synapses were always found on dendritic shafts or somata. Often, synapses are located close to the appendages. These data indicate that the transient appendages are not the place where ingrowing afferent fibers make their synapses. The available information about transient dendritic appendages suggests, that they may be involved in short-term contacts with ingrowing axons, without being themselves the final site of the synaptic contact.
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Affiliation(s)
- R Linke
- Institute of Anatomy, University of Freiburg, Germany
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28
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Zafirov S, Heimrich B, Frotscher M. Dendritic development of dentate granule cells in the absence of their specific extrinsic afferents. J Comp Neurol 1994; 345:472-80. [PMID: 7929913 DOI: 10.1002/cne.903450312] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Dendrites and spines are postsynaptic structures that develop in association with presynaptic fibers. Recent studies have shown that granule cells of the fascia dentata survive in slice cultures and differentiate in a manner known from in situ studies. However, all extrinsic afferent fibers are absent under culture conditions. In the present study, we study whether dendrites and spines of granule cells in slice cultures differentiate normally, although they are not contacted by their normal layer-specific afferents. Slices of hippocampus were prepared from rat pups at the day of birth. After 5, 10, 15, and 20 days of incubation, granule cells in these cultures were Golgi impregnated. For comparison, perfusion-fixed hippocampal sections of 5-, 10-, 15-, and 20-day-old rats were impregnated the same way. Our results show that the total density of spines on granule cell dendrites in culture increased as in perfusion-fixed animals. However, after 20 days of incubation, the absolute number of dendritic spines on cultured neurons was reduced because of a reduction of peripheral dendrites. This reduction was accompanied by an increase in the number of stem dendrites originating from the perikaryon. The density of spines on these proximal dendrites was larger in cultured granule cells than in controls. Our results suggest that the lack of major extrinsic (entorhinal) afferents that normally terminate on peripheral granule cell dendrites causes retraction of these dendrites. At the same time, there is growth of proximal dendritic portions. Proximal dendrites are targets of associational fibers, which are known to sprout under these culture conditions.
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Affiliation(s)
- S Zafirov
- Institute of Anatomy, University of Freiburg, Germany
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29
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Jorritsma-Byham B, Witter MP, Wouterlood FG. Combined anterograde tracing with biotinylated dextran-amine, retrograde tracing with fast blue and intracellular filling of neurons with lucifer yellow: an electron microscopic method. J Neurosci Methods 1994; 52:153-60. [PMID: 7526083 DOI: 10.1016/0165-0270(94)90124-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In order to determine the presence of synaptic connectivity between fibres originating from a specific source and neurones with a known morphology and known fibre projection, we have introduced a method for electron microscopy that combines three techniques: retrograde fluorescent tracing, anterograde tracing using biotinylated dextran-amine and intracellular injection of Lucifer Yellow (LY) in lightly fixed brain slices. Neurones in the rat entorhinal cortex that project to the infralimbic cortex and that might be in synaptic contact with fibres originating in the dorsal subiculum served as a model. After surgical application of the tracers and a survival period enabling transport, the brain was fixed and vibratome slices 300 microns thick were prepared in which retrogradely labelled cells were intracellularly injected with LY. This substance and the transported biotinylated dextran-amine were converted into different electron-dense labels. First, LY immunocytochemistry was conducted, then followed by silver-gold enhancement of the immunoprecipitate. Subsequently, the tissue sections were treated with an avidin-biotin-horseradish peroxidase complex and subjected to a diaminobenzidine-peroxide reaction. This protocol resulted in labelling of biotinylated dextran-amine-positive fibres and terminals that could easily be differentiated from the LY-positive neuronal elements and also showed well preserved ultrastructural detail.
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Affiliation(s)
- B Jorritsma-Byham
- Graduate School of Neurosciences Amsterdam, Research Institute Neurosciences Vrije Universiteit, Faculty of Medicine, Amsterdam, The Netherlands
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