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Maher EE, Briegel AC, Imtiaz S, Fox MA, Golino H, Erisir A. 3D electron microscopy and volume-based bouton sorting reveal the selectivity of inputs onto geniculate relay cell and interneuron dendrite segments. Front Neuroanat 2023; 17:1150747. [PMID: 37007643 PMCID: PMC10064015 DOI: 10.3389/fnana.2023.1150747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 02/27/2023] [Indexed: 03/19/2023] Open
Abstract
Introduction The visual signals evoked at the retinal ganglion cells are modified and modulated by various synaptic inputs that impinge on lateral geniculate nucleus cells before they are sent to the cortex. The selectivity of geniculate inputs for clustering or forming microcircuits on discrete dendritic segments of geniculate cell types may provide the structural basis for network properties of the geniculate circuitry and differential signal processing through the parallel pathways of vision. In our study, we aimed to reveal the patterns of input selectivity on morphologically discernable relay cell types and interneurons in the mouse lateral geniculate nucleus. Methods We used two sets of Scanning Blockface Electron Microscopy (SBEM) image stacks and Reconstruct software to manually reconstruct of terminal boutons and dendrite segments. First, using an unbiased terminal sampling (UTS) approach and statistical modeling, we identified the criteria for volume-based sorting of geniculate boutons into their putative origins. Geniculate terminal boutons that were sorted in retinal and non-retinal categories based on previously described mitochondrial morphology, could further be sorted into multiple subpopulations based on their bouton volume distributions. Terminals deemed non-retinal based on the morphological criteria consisted of five distinct subpopulations, including small-sized putative corticothalamic and cholinergic boutons, two medium-sized putative GABAergic inputs, and a large-sized bouton type that contains dark mitochondria. Retinal terminals also consisted of four distinct subpopulations. The cutoff criteria for these subpopulations were then applied to datasets of terminals that synapse on reconstructed dendrite segments of relay cells or interneurons. Results Using a network analysis approach, we found an almost complete segregation of retinal and cortical terminals on putative X-type cell dendrite segments characterized by grape-like appendages and triads. On these cells, interneuron appendages intermingle with retinal and other medium size terminals to form triads within glomeruli. In contrast, a second, presumed Y-type cell displayed dendrodendritic puncta adherentia and received all terminal types without a selectivity for synapse location; these were not engaged in triads. Furthermore, the contribution of retinal and cortical synapses received by X-, Y- and interneuron dendrites differed such that over 60% of inputs to interneuron dendrites were from the retina, as opposed to 20% and 7% to X- and Y-type cells, respectively. Conclusion The results underlie differences in network properties of synaptic inputs from distinct origins on geniculate cell types.
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Affiliation(s)
- Erin E Maher
- Department of Psychology, University of Virginia, Charlottesville, VA, United States
| | - Alex C Briegel
- Department of Psychology, University of Virginia, Charlottesville, VA, United States
| | - Shahrozia Imtiaz
- Department of Psychology, University of Virginia, Charlottesville, VA, United States
| | - Michael A Fox
- School of Neuroscience, Virginia Tech, Blacksburg, VA, United States
- Fralin Biomedical Research Institute, Roanoke, VA, United States
| | - Hudson Golino
- Department of Psychology, University of Virginia, Charlottesville, VA, United States
| | - Alev Erisir
- Department of Psychology, University of Virginia, Charlottesville, VA, United States
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Mikhalkin AA, Nikitina NI, Merkulyeva NS. Age-Related Changes in Soma Size of Y Neurons in the Cat Dorsal Lateral Geniculate Nucleus: Dorsoventral and Centroperipheral Gradients. J EVOL BIOCHEM PHYS+ 2022. [DOI: 10.1134/s0022093022060126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Sabbagh U, Govindaiah G, Somaiya RD, Ha RV, Wei JC, Guido W, Fox MA. Diverse GABAergic neurons organize into subtype-specific sublaminae in the ventral lateral geniculate nucleus. J Neurochem 2021; 159:479-497. [PMID: 32497303 PMCID: PMC8210463 DOI: 10.1111/jnc.15101] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/14/2020] [Accepted: 05/19/2020] [Indexed: 12/16/2022]
Abstract
In the visual system, retinal axons convey visual information from the outside world to dozens of distinct retinorecipient brain regions and organize that information at several levels, including either at the level of retinal afferents, cytoarchitecture of intrinsic retinorecipient neurons, or a combination of the two. Two major retinorecipient nuclei which are densely innervated by retinal axons are the dorsal lateral geniculate nucleus, which is important for classical image-forming vision, and ventral LGN (vLGN), which is associated with non-image-forming vision. The neurochemistry, cytoarchitecture, and retinothalamic connectivity in vLGN remain unresolved, raising fundamental questions of how it receives and processes visual information. To shed light on these important questions, used in situ hybridization, immunohistochemistry, and genetic reporter lines to identify and characterize novel neuronal cell types in mouse vLGN. Not only were a high percentage of these cells GABAergic, we discovered transcriptomically distinct GABAergic cell types reside in the two major laminae of vLGN, the retinorecipient, external vLGN (vLGNe) and the non-retinorecipient, internal vLGN (vLGNi). Furthermore, within vLGNe, we identified transcriptionally distinct subtypes of GABAergic cells that are distributed into four adjacent sublaminae. Using trans-synaptic viral tracing and in vitro electrophysiology, we found cells in each these vLGNe sublaminae receive monosynaptic inputs from retina. These results not only identify novel subtypes of GABAergic cells in vLGN, they suggest the subtype-specific laminar distribution of retinorecipient cells in vLGNe may be important for receiving, processing, and transmitting light-derived signals in parallel channels of the subcortical visual system.
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Affiliation(s)
- Ubadah Sabbagh
- Center for Neurobiology ResearchFralin Biomedical Research Institute at Virginia Tech CarilionRoanokeVAUSA
- Graduate Program in Translational Biology, Medicine, and HealthVirginia TechBlacksburgVAUSA
| | - Gubbi Govindaiah
- Department of Anatomical Sciences and NeurobiologyUniversity of Louisville School of MedicineLouisvilleKYUSA
| | - Rachana D. Somaiya
- Center for Neurobiology ResearchFralin Biomedical Research Institute at Virginia Tech CarilionRoanokeVAUSA
- Graduate Program in Translational Biology, Medicine, and HealthVirginia TechBlacksburgVAUSA
| | - Ryan V. Ha
- School of NeuroscienceVirginia TechBlacksburgVAUSA
| | - Jessica C. Wei
- NeuroSURFFralin Biomedical Research Institute at Virginia Tech CarilionRoanokeVAUSA
| | - William Guido
- Department of Anatomical Sciences and NeurobiologyUniversity of Louisville School of MedicineLouisvilleKYUSA
| | - Michael A. Fox
- Center for Neurobiology ResearchFralin Biomedical Research Institute at Virginia Tech CarilionRoanokeVAUSA
- School of NeuroscienceVirginia TechBlacksburgVAUSA
- Department of Biological SciencesVirginia TechBlacksburgVAUSA
- Department of PediatricsVirginia Tech Carilion School of MedicineRoanokeVAUSA
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O'Reilly C, Iavarone E, Yi J, Hill SL. Rodent somatosensory thalamocortical circuitry: Neurons, synapses, and connectivity. Neurosci Biobehav Rev 2021; 126:213-235. [PMID: 33766672 DOI: 10.1016/j.neubiorev.2021.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 02/15/2021] [Accepted: 03/14/2021] [Indexed: 01/21/2023]
Abstract
As our understanding of the thalamocortical system deepens, the questions we face become more complex. Their investigation requires the adoption of novel experimental approaches complemented with increasingly sophisticated computational modeling. In this review, we take stock of current data and knowledge about the circuitry of the somatosensory thalamocortical loop in rodents, discussing common principles across modalities and species whenever appropriate. We review the different levels of organization, including the cells, synapses, neuroanatomy, and network connectivity. We provide a complete overview of this system that should be accessible for newcomers to this field while nevertheless being comprehensive enough to serve as a reference for seasoned neuroscientists and computational modelers studying the thalamocortical system. We further highlight key gaps in data and knowledge that constitute pressing targets for future experimental work. Filling these gaps would provide invaluable information for systematically unveiling how this system supports behavioral and cognitive processes.
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Affiliation(s)
- Christian O'Reilly
- Azrieli Centre for Autism Research, Montreal Neurological Institute, McGill University, Montreal, Canada; Ronin Institute, Montclair, NJ, USA; Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland.
| | - Elisabetta Iavarone
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
| | - Jane Yi
- Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Sean L Hill
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland; Department of Psychiatry, University of Toronto, Toronto, Canada; Centre for Addiction and Mental Health, Toronto, Canada.
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Kimura A. Cross-modal modulation of cell activity by sound in first-order visual thalamic nucleus. J Comp Neurol 2020; 528:1917-1941. [PMID: 31983057 DOI: 10.1002/cne.24865] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 12/19/2019] [Accepted: 01/16/2020] [Indexed: 12/16/2022]
Abstract
Cross-modal auditory influence on cell activity in the primary visual cortex emerging at short latencies raises the possibility that the first-order visual thalamic nucleus, which is considered dedicated to unimodal visual processing, could contribute to cross-modal sensory processing, as has been indicated in the auditory and somatosensory systems. To test this hypothesis, the effects of sound stimulation on visual cell activity in the dorsal lateral geniculate nucleus were examined in anesthetized rats, using juxta-cellular recording and labeling techniques. Visual responses evoked by light (white LED) were modulated by sound (noise burst) given simultaneously or 50-400 ms after the light, even though sound stimuli alone did not evoke cell activity. Alterations of visual response were observed in 71% of cells (57/80) with regard to response magnitude, latency, and/or burst spiking. Suppression predominated in response magnitude modulation, but de novo responses were also induced by combined stimulation. Sound affected not only onset responses but also late responses. Late responses were modulated by sound given before or after onset responses. Further, visual responses evoked by the second light stimulation of a double flash with a 150-700 ms interval were also modulated by sound given together with the first light stimulation. In morphological analysis of labeled cells projection cells comparable to X-, Y-, and W-like cells and interneurons were all susceptible to auditory influence. These findings suggest that the first-order visual thalamic nucleus incorporates auditory influence into parallel and complex thalamic visual processing for cross-modal modulation of visual attention and perception.
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Affiliation(s)
- Akihisa Kimura
- Department of Physiology, Wakayama Medical University, Wakayama, Japan
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Kanari L, Dłotko P, Scolamiero M, Levi R, Shillcock J, Hess K, Markram H. A Topological Representation of Branching Neuronal Morphologies. Neuroinformatics 2019; 16:3-13. [PMID: 28975511 PMCID: PMC5797226 DOI: 10.1007/s12021-017-9341-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Many biological systems consist of branching structures that exhibit a wide variety of shapes. Our understanding of their systematic roles is hampered from the start by the lack of a fundamental means of standardizing the description of complex branching patterns, such as those of neuronal trees. To solve this problem, we have invented the Topological Morphology Descriptor (TMD), a method for encoding the spatial structure of any tree as a "barcode", a unique topological signature. As opposed to traditional morphometrics, the TMD couples the topology of the branches with their spatial extents by tracking their topological evolution in 3-dimensional space. We prove that neuronal trees, as well as stochastically generated trees, can be accurately categorized based on their TMD profiles. The TMD retains sufficient global and local information to create an unbiased benchmark test for their categorization and is able to quantify and characterize the structural differences between distinct morphological groups. The use of this mathematically rigorous method will advance our understanding of the anatomy and diversity of branching morphologies.
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Affiliation(s)
- Lida Kanari
- Blue Brain Project-EPFL, Geneva, Switzerland.
| | - Paweł Dłotko
- Department of Mathematics, Swansea University, Swansea, UK
| | - Martina Scolamiero
- Laboratory for Topology and Neuroscience at the Brain Mind Institute, EPFL, Geneva, Switzerland
| | - Ran Levi
- Institute of Mathematics, University of Aberdeen, Aberdeen, UK
| | | | - Kathryn Hess
- Laboratory for Topology and Neuroscience at the Brain Mind Institute, EPFL, Geneva, Switzerland
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Chrobok L, Palus‐Chramiec K, Jeczmien‐Lazur JS, Blasiak T, Lewandowski MH. Gamma and infra-slow oscillations shape neuronal firing in the rat subcortical visual system. J Physiol 2018; 596:2229-2250. [PMID: 29577327 PMCID: PMC5983133 DOI: 10.1113/jp275563] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 03/21/2018] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Neuronal oscillations observed in sensory systems are physiological carriers of information about stimulus features. Rhythm in the infra-slow range, originating from the retina, was previously found in the firing of subcortical visual system nuclei involved in both image and non-image forming functions. The present study shows that the firing of neurons in the lateral geniculate nucleus is also governed by gamma oscillation (∼35 Hz) time-locked to high phase of infra-slow rhythm that codes the intensity of transient light stimulation. We show that both physiological rhythms are synchronized within and between ipsilateral nuclei of the subcortical visual system and are dependent on retinal activity. The present study shows that neurophysiological oscillations characterized by various frequencies not only coexist in the subcortical visual system, but also are subjected to complex interference and synchronization processes. ABSTRACT The physiological function of rhythmic firing in the neuronal networks of sensory systems has been linked with information coding. Also, neuronal oscillations in different frequency bands often change as a signature of brain state or sensory processing. Infra-slow oscillation (ISO) in the neuronal firing dependent on the retinal network has been described previously in the structures of the subcortical visual system. In the present study, we show for the first time that firing of ISO neurons in the lateral geniculate nucleus is also characterized by a harmonic discharge pattern (i.e. action potentials are separated by the intervals governed by fundamental frequency in the gamma range: ∼35 Hz). A similar phenomenon was recently described in the suprachiasmatic nuclei of the hypothalamus: the master biological clock. We found that both gamma and ISO rhythms were synchronized within and between ipsilateral nuclei of the subcortical visual system and were dependent on the retinal activity of the contralateral eye. These oscillatory patterns were differentially influenced by transient and prolonged light stimulation with respect to both frequency change direction and sustainability. The results of the present study show that the firing pattern of neurons in the subcortical visual system is shaped by oscillations from infra-slow and gamma frequency bands that are plausibly generated by the retinal network. Additionally, the results demonstrate that both rhythms are not a distinctive feature of image or non-image forming visual systems but, instead, they comprise two channels carrying distinctive properties of photic information.
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Affiliation(s)
- Lukasz Chrobok
- Department of Neurophysiology and ChronobiologyInstitute of Zoology and Biomedical ResearchJagiellonian University in KrakowKrakowPoland
| | - Katarzyna Palus‐Chramiec
- Department of Neurophysiology and ChronobiologyInstitute of Zoology and Biomedical ResearchJagiellonian University in KrakowKrakowPoland
| | - Jagoda Stanislawa Jeczmien‐Lazur
- Department of Neurophysiology and ChronobiologyInstitute of Zoology and Biomedical ResearchJagiellonian University in KrakowKrakowPoland
| | - Tomasz Blasiak
- Department of Neurophysiology and ChronobiologyInstitute of Zoology and Biomedical ResearchJagiellonian University in KrakowKrakowPoland
| | - Marian Henryk Lewandowski
- Department of Neurophysiology and ChronobiologyInstitute of Zoology and Biomedical ResearchJagiellonian University in KrakowKrakowPoland
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Chrobok L, Palus-Chramiec K, Chrzanowska A, Kepczynski M, Lewandowski MH. Multiple excitatory actions of orexins upon thalamo-cortical neurons in dorsal lateral geniculate nucleus - implications for vision modulation by arousal. Sci Rep 2017; 7:7713. [PMID: 28794459 PMCID: PMC5550457 DOI: 10.1038/s41598-017-08202-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 07/06/2017] [Indexed: 01/08/2023] Open
Abstract
The orexinergic system of the lateral hypothalamus plays a crucial role in maintaining wakefulness and mediating arousal in a circadian time-dependent manner. Due to the extensive connections of orexinergic neurons, both orexins (OXA and OXB) exert mainly excitatory effects upon remote brain areas, including the thalamus. The dorsal lateral geniculate nucleus (DLG) is a relay thalamic centre for the visual system. Its thalamo-cortical (TC) neurons convey photic information from the retina to the primary visual cortex. The present study shows that orexins are powerful modulators of neuronal activity in the DLG. OXA directly depolarised the majority of neurons tested, acting predominately on postsynaptic OX2 receptors. Moreover, OXA was found to increase excitability and enhance neuronal responses to both glutamate and γ-aminobutyric acid (GABA). Mechanistic studies showed the involvement of voltage-gated calcium currents and GIRK channels in the observed depolarisations. Immunohistochemical staining showed sparse orexinergic innervation of the DLG during the light phase, with increased density at night. We hypothesise that the depolarising effects of orexins upon DLG neurons may facilitate signal transmission through the visual thalamo-cortical pathway during behavioural arousal. Thus, the action of orexin on DLG TC neurons may underlie the circadian/behavioural modulation of vision.
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Affiliation(s)
- Lukasz Chrobok
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Katarzyna Palus-Chramiec
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Anna Chrzanowska
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Mariusz Kepczynski
- Faculty of Chemistry, Jagiellonian University in Krakow, Ingardena 3 Street, 30-060, Krakow, Poland
| | - Marian Henryk Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland.
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Monavarfeshani A, Sabbagh U, Fox MA. Not a one-trick pony: Diverse connectivity and functions of the rodent lateral geniculate complex. Vis Neurosci 2017; 34:E012. [PMID: 28965517 PMCID: PMC5755970 DOI: 10.1017/s0952523817000098] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Often mislabeled as a simple relay of sensory information, the thalamus is a complicated structure with diverse functions. This diversity is exemplified by roles visual thalamus plays in processing and transmitting light-derived stimuli. Such light-derived signals are transmitted to the thalamus by retinal ganglion cells (RGCs), the sole projection neurons of the retina. Axons from RGCs innervate more than ten distinct nuclei within thalamus, including those of the lateral geniculate complex. Nuclei within the lateral geniculate complex of nocturnal rodents, which include the dorsal lateral geniculate nucleus (dLGN), ventral lateral geniculate nucleus (vLGN), and intergeniculate leaflet (IGL), are each densely innervated by retinal projections, yet, exhibit distinct cytoarchitecture and connectivity. These features suggest that each nucleus within this complex plays a unique role in processing and transmitting light-derived signals. Here, we review the diverse cytoarchitecture and connectivity of these nuclei in nocturnal rodents, in an effort to highlight roles for dLGN in vision and for vLGN and IGL in visuomotor, vestibular, ocular, and circadian function.
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Affiliation(s)
- Aboozar Monavarfeshani
- Developmental and Translational Neurobiology Center,Virginia Tech Carilion Research Institute,Roanoke,Virginia
| | - Ubadah Sabbagh
- Developmental and Translational Neurobiology Center,Virginia Tech Carilion Research Institute,Roanoke,Virginia
| | - Michael A Fox
- Developmental and Translational Neurobiology Center,Virginia Tech Carilion Research Institute,Roanoke,Virginia
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Morgan JL, Berger DR, Wetzel AW, Lichtman JW. The Fuzzy Logic of Network Connectivity in Mouse Visual Thalamus. Cell 2016; 165:192-206. [PMID: 27015312 DOI: 10.1016/j.cell.2016.02.033] [Citation(s) in RCA: 152] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/11/2015] [Accepted: 02/12/2016] [Indexed: 11/17/2022]
Abstract
In an attempt to chart parallel sensory streams passing through the visual thalamus, we acquired a 100-trillion-voxel electron microscopy (EM) dataset and identified cohorts of retinal ganglion cell axons (RGCs) that innervated each of a diverse group of postsynaptic thalamocortical neurons (TCs). Tracing branches of these axons revealed the set of TCs innervated by each RGC cohort. Instead of finding separate sensory pathways, we found a single large network that could not be easily subdivided because individual RGCs innervated different kinds of TCs and different kinds of RGCs co-innervated individual TCs. We did find conspicuous network subdivisions organized on the basis of dendritic rather than neuronal properties. This work argues that, in the thalamus, neural circuits are not based on a canonical set of connections between intrinsically different neuronal types but, rather, may arise by experience-based mixing of different kinds of inputs onto individual postsynaptic cells.
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Affiliation(s)
- Josh Lyskowski Morgan
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA.
| | - Daniel Raimund Berger
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | | | - Jeff William Lichtman
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA.
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Liu M, Guo L, Salt TE, Cordeiro MF. Dendritic changes in rat visual pathway associated with experimental ocular hypertension. Curr Eye Res 2014; 39:953-63. [PMID: 24754236 DOI: 10.3109/02713683.2014.884594] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
PURPOSE Increasing evidence shows that structural changes in dendrites play an important role in neuronal degenerative processes. The aims of this study were to characterize and delineate morphological changes of dendrites in retinal ganglion cells (RGCs) and their central target neurons in the superior colliculus (SC) and lateral geniculate nucleus (LGN) in experimental rat glaucoma. METHODS Chronic ocular hypertension (OHT) was surgically induced in rats and animals were sacrificed at 1, 4, 8, 16 and 32 weeks following IOP elevation. Animals without IOP elevation served as normal control. Dendritic morphology of neurons was visualized by ex vivo DiI labelling using confocal microscopy and dendritic length and number was quantified using Image J. RESULTS We found significant dendritic shrinkage (p < 0.001) and loss (p < 0.001) in RGCs and neurons in the SC and LGN in OHT animals compared to age-matched controls. Analysis of the temporal morphological profiles among them revealed the RGCs to have the earliest changes compared to the SC and LGN although the most prominent changes occurred in the SC. CONCLUSION Our study has demonstrated that OHT results in dendritic changes of the neurons throughout the visual pathways, from RGCs to SC cells and LGN cells, suggesting that both the retina and the brain should be targeted when considering diagnosis and therapeutic strategies for glaucoma.
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Affiliation(s)
- Meng Liu
- Glaucoma and Retinal Neurodegeneration Research Group, UCL Institute of Ophthalmology , London , United Kingdom
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Hendrickson ML, Ling C, Kalil RE. Degeneration of axotomized projection neurons in the rat dLGN: temporal progression of events and their mitigation by a single administration of FGF2. PLoS One 2012; 7:e46918. [PMID: 23144793 PMCID: PMC3489851 DOI: 10.1371/journal.pone.0046918] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 09/06/2012] [Indexed: 12/13/2022] Open
Abstract
Removal of visual cortex in the rat axotomizes projection neurons in the dorsal lateral geniculate nucleus (dLGN), leading to cytological and structural changes and apoptosis. Biotinylated dextran amine was injected into the visual cortex to label dLGN projection neurons retrogradely prior to removing the cortex in order to quantify the changes in the dendritic morphology of these neurons that precede cell death. At 12 hours after axotomy we observed a loss of appendages and the formation of varicosities in the dendrites of projection neurons. During the next 7 days, the total number of dendrites and the cross-sectional areas of the dendritic arbors of projection neurons declined to about 40% and 20% of normal, respectively. The response of dLGN projection neurons to axotomy was asynchronous, but the sequence of structural changes in individual neurons was similar; namely, disruption of dendrites began within hours followed by cell soma atrophy and nuclear condensation that commenced after the loss of secondary dendrites had occurred. However, a single administration of fibroblast growth factor-2 (FGF2), which mitigates injury-induced neuronal cell death in the dLGN when given at the time of axotomy, markedly reduced the dendritic degeneration of projection neurons. At 3 and 7 days after axotomy the number of surviving dendrites of dLGN projection neurons in FGF-2 treated rats was approximately 50% greater than in untreated rats, and the cross-sectional areas of dendritic arbors were approximately 60% and 50% larger. Caspase-3 activity in axotomized dLGN projection neurons was determined by immunostaining for fractin (fractin-IR), an actin cleavage product produced exclusively by activated caspase-3. Fractin-IR was seen in some dLGN projection neurons at 36 hours survival, and it increased slightly by 3 days. A marked increase in reactivity was seen by 7 days, with the entire dLGN filled with dense fractin-IR in neuronal cell somas and dendrites.
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Affiliation(s)
- Michael L. Hendrickson
- W.M. Keck Laboratory for Biological Imaging, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Changying Ling
- Department of Surgery, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ronald E. Kalil
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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Ling C, Hendrickson ML, Kalil RE. Resolving the detailed structure of cortical and thalamic neurons in the adult rat brain with refined biotinylated dextran amine labeling. PLoS One 2012; 7:e45886. [PMID: 23144777 PMCID: PMC3489877 DOI: 10.1371/journal.pone.0045886] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 08/23/2012] [Indexed: 02/07/2023] Open
Abstract
Biotinylated dextran amine (BDA) has been used frequently for both anterograde and retrograde pathway tracing in the central nervous system. Typically, BDA labels axons and cell somas in sufficient detail to identify their topographical location accurately. However, BDA labeling often has proved to be inadequate to resolve the fine structural details of axon arbors or the dendrites of neurons at a distance from the site of BDA injection. To overcome this limitation, we varied several experimental parameters associated with the BDA labeling of neurons in the adult rat brain in order to improve the sensitivity of the method. Specifically, we compared the effect on labeling sensitivity of: (a) using 3,000 or 10,000 MW BDA; (b) injecting different volumes of BDA; (c) co-injecting BDA with NMDA; and (d) employing various post-injection survival times. Following the extracellular injection of BDA into the visual cortex, labeled cells and axons were observed in both cortical and thalamic areas of all animals studied. However, the detailed morphology of axon arbors and distal dendrites was evident only under optimal conditions for BDA labeling that take into account the: molecular weight of the BDA used, concentration and volume of BDA injected, post-injection survival time, and toning of the resolved BDA with gold and silver. In these instances, anterogradely labeled axons and retrogradely labeled dendrites were resolved in fine detail, approximating that which can be achieved with intracellularly injected compounds such as biocytin or fluorescent dyes.
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Affiliation(s)
- Changying Ling
- Department of Surgery, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Michael L. Hendrickson
- W.M. Keck Laboratory for Biological Imaging, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ronald E. Kalil
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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