1
|
Wisner SR, Saha A, Grimes WN, Mizerska K, Kolarik HJ, Wallin J, Diamond JS, Sinha R, Hoon M. Sensory deprivation arrests cellular and synaptic development of the night-vision circuitry in the retina. Curr Biol 2023; 33:4415-4429.e3. [PMID: 37769662 PMCID: PMC10615854 DOI: 10.1016/j.cub.2023.08.087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/10/2023] [Accepted: 08/30/2023] [Indexed: 10/03/2023]
Abstract
Experience regulates synapse formation and function across sensory circuits. How inhibitory synapses in the mammalian retina are sculpted by visual cues remains unclear. By use of a sensory deprivation paradigm, we find that visual cues regulate maturation of two GABA synapse types (GABAA and GABAC receptor synapses), localized across the axon terminals of rod bipolar cells (RBCs)-second-order retinal neurons integral to the night-vision circuit. Lack of visual cues causes GABAA synapses at RBC terminals to retain an immature receptor configuration with slower response profiles and prevents receptor recruitment at GABAC synapses. Additionally, the organizing protein for both these GABA synapses, LRRTM4, is not clustered at dark-reared RBC synapses. Ultrastructurally, the total number of ribbon-output/inhibitory-input synapses across RBC terminals remains unaltered by sensory deprivation, although ribbon synapse output sites are misarranged when the circuit develops without visual cues. Intrinsic electrophysiological properties of RBCs and expression of chloride transporters across RBC terminals are additionally altered by sensory deprivation. Introduction to normal 12-h light-dark housing conditions facilitates maturation of dark-reared RBC GABA synapses and restoration of intrinsic RBC properties, unveiling a new element of light-dependent retinal cellular and synaptic plasticity.
Collapse
Affiliation(s)
- Serena R Wisner
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA; Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI 53705, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Aindrila Saha
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA; Cellular and Molecular Biology Program, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - William N Grimes
- Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kamila Mizerska
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Hannah J Kolarik
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Julie Wallin
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Jeffrey S Diamond
- Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Raunak Sinha
- McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI 53705, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA.
| |
Collapse
|
2
|
Dendro-somatic synaptic inputs to ganglion cells contradict receptive field and connectivity conventions in the mammalian retina. Curr Biol 2022; 32:315-328.e4. [PMID: 34822767 PMCID: PMC8792273 DOI: 10.1016/j.cub.2021.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 10/08/2021] [Accepted: 11/02/2021] [Indexed: 01/26/2023]
Abstract
The morphology of retinal neurons strongly influences their physiological function. Ganglion cell (GC) dendrites ramify in distinct strata of the inner plexiform layer (IPL) so that GCs responding to light increments (ON) or decrements (OFF) receive appropriate excitatory inputs. This vertical stratification prescribes response polarity and ensures consistent connectivity between cell types, whereas the lateral extent of GC dendritic arbors typically dictates receptive field (RF) size. Here, we identify circuitry in mouse retina that contradicts these conventions. AII amacrine cells are interneurons understood to mediate "crossover" inhibition by relaying excitatory input from the ON layer to inhibitory outputs in the OFF layer. Ultrastructural and physiological analyses show, however, that some AIIs deliver powerful inhibition to OFF GC somas and proximal dendrites in the ON layer, rendering the inhibitory RFs of these GCs smaller than their dendritic arbors. This OFF pathway, avoiding entirely the OFF region of the IPL, challenges several tenets of retinal circuitry. These results also indicate that subcellular synaptic organization can vary within a single population of neurons according to their proximity to potential postsynaptic targets.
Collapse
|
3
|
Sinha R, Grimes WN, Wallin J, Ebbinghaus BN, Luu K, Cherry T, Rieke F, Rudolph U, Wong RO, Hoon M. Transient expression of a GABA receptor subunit during early development is critical for inhibitory synapse maturation and function. Curr Biol 2021; 31:4314-4326.e5. [PMID: 34433078 DOI: 10.1016/j.cub.2021.07.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 06/29/2021] [Accepted: 07/23/2021] [Indexed: 10/20/2022]
Abstract
Developing neural circuits, including GABAergic circuits, switch receptor types. But the role of early GABA receptor expression for establishment of functional inhibitory circuits remains unclear. Tracking the development of GABAergic synapses across axon terminals of retinal bipolar cells (BCs), we uncovered a crucial role of early GABAA receptor expression for the formation and function of presynaptic inhibitory synapses. Specifically, early α3-subunit-containing GABAA (GABAAα3) receptors are a key developmental organizer. Before eye opening, GABAAα3 gives way to GABAAα1 at individual BC presynaptic inhibitory synapses. The developmental downregulation of GABAAα3 is independent of GABAAα1 expression. Importantly, lack of early GABAAα3 impairs clustering of GABAAα1 and formation of functional GABAA synapses across mature BC terminals. This impacts the sensitivity of visual responses transmitted through the circuit. Lack of early GABAAα3 also perturbs aggregation of LRRTM4, the organizing protein at GABAergic synapses of rod BC terminals, and their arrangement of output ribbon synapses.
Collapse
Affiliation(s)
- Raunak Sinha
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - William N Grimes
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA; National Institute of Neurological Disease and Stroke, NIH, Bethesda, MD, USA
| | - Julie Wallin
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Briana N Ebbinghaus
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Kelsey Luu
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA, USA
| | - Timothy Cherry
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA, USA; Department of Pediatrics, University of Washington-Seattle and the Brotman Baty Institute for Precision Medicine, Seattle, WA, USA
| | - Fred Rieke
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA
| | - Uwe Rudolph
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Mrinalini Hoon
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA.
| |
Collapse
|
4
|
Nagy J, Ebbinghaus B, Hoon M, Sinha R. GABA A presynaptic inhibition regulates the gain and kinetics of retinal output neurons. eLife 2021; 10:60994. [PMID: 33904401 PMCID: PMC8110304 DOI: 10.7554/elife.60994] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 04/06/2021] [Indexed: 12/16/2022] Open
Abstract
Output signals of neural circuits, including the retina, are shaped by a combination of excitatory and inhibitory signals. Inhibitory signals can act presynaptically on axon terminals to control neurotransmitter release and regulate circuit function. However, it has been difficult to study the role of presynaptic inhibition in most neural circuits due to lack of cell type-specific and receptor type-specific perturbations. In this study, we used a transgenic approach to selectively eliminate GABAA inhibitory receptors from select types of second-order neurons - bipolar cells - in mouse retina and examined how this affects the light response properties of the well-characterized ON alpha ganglion cell retinal circuit. Selective loss of GABAA receptor-mediated presynaptic inhibition causes an enhanced sensitivity and slower kinetics of light-evoked responses from ON alpha ganglion cells thus highlighting the role of presynaptic inhibition in gain control and temporal filtering of sensory signals in a key neural circuit in the mammalian retina.
Collapse
Affiliation(s)
- Jenna Nagy
- Department of Neuroscience, University of WisconsinMadisonUnited States
- McPherson Eye Research Institute, University of WisconsinMadisonUnited States
- Cellular and Molecular Pathology Training Program, University of WisconsinMadisonUnited States
| | - Briana Ebbinghaus
- McPherson Eye Research Institute, University of WisconsinMadisonUnited States
- Department of Ophthalmology and Visual Sciences, University of WisconsinMadisonUnited States
- Neuroscience Training Program, University of WisconsinMadisonUnited States
| | - Mrinalini Hoon
- Department of Neuroscience, University of WisconsinMadisonUnited States
- McPherson Eye Research Institute, University of WisconsinMadisonUnited States
- Department of Ophthalmology and Visual Sciences, University of WisconsinMadisonUnited States
| | - Raunak Sinha
- Department of Neuroscience, University of WisconsinMadisonUnited States
- McPherson Eye Research Institute, University of WisconsinMadisonUnited States
- Department of Ophthalmology and Visual Sciences, University of WisconsinMadisonUnited States
| |
Collapse
|
5
|
Sawant A, Ebbinghaus BN, Bleckert A, Gamlin C, Yu WQ, Berson D, Rudolph U, Sinha R, Hoon M. Organization and emergence of a mixed GABA-glycine retinal circuit that provides inhibition to mouse ON-sustained alpha retinal ganglion cells. Cell Rep 2021; 34:108858. [PMID: 33730586 PMCID: PMC8030271 DOI: 10.1016/j.celrep.2021.108858] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 12/07/2020] [Accepted: 02/19/2021] [Indexed: 12/04/2022] Open
Abstract
In the retina, amacrine interneurons inhibit retinal ganglion cell (RGC) dendrites to shape retinal output. Amacrine cells typically use either GABA or glycine to exert synaptic inhibition. Here, we combined transgenic tools with immunohistochemistry, electrophysiology, and 3D electron microscopy to determine the composition and organization of inhibitory synapses across the dendritic arbor of a well-characterized RGC type in the mouse retina: the ON-sustained alpha RGC. We find mixed GABA-glycine receptor synapses across this RGC type, unveiling the existence of "mixed" inhibitory synapses in the retinal circuit. Presynaptic amacrine boutons with dual release sites are apposed to ON-sustained alpha RGC postsynapses. We further reveal the sequence of postsynaptic assembly for these mixed synapses: GABA receptors precede glycine receptors, and a lack of early GABA receptor expression impedes the recruitment of glycine receptors. Together our findings uncover the organization and developmental profile of an additional motif of inhibition in the mammalian retina.
Collapse
Affiliation(s)
- Abhilash Sawant
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA
| | - Briana N Ebbinghaus
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Adam Bleckert
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Clare Gamlin
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - Wan-Qing Yu
- Department of Biological Structure, University of Washington, Seattle, WA, USA
| | - David Berson
- Department of Neuroscience, Brown University, Providence, RI, USA
| | - Uwe Rudolph
- Department of Comparative Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Champaign, IL, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Champaign, IL, USA
| | - Raunak Sinha
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA
| | - Mrinalini Hoon
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, USA; McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI, USA.
| |
Collapse
|
6
|
Ly C, Shimizu AJ, Vargas MV, Duim WC, Wender PA, Olson DE. Bryostatin 1 Promotes Synaptogenesis and Reduces Dendritic Spine Density in Cortical Cultures through a PKC-Dependent Mechanism. ACS Chem Neurosci 2020; 11:1545-1554. [PMID: 32437156 PMCID: PMC7332236 DOI: 10.1021/acschemneuro.0c00175] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The marine natural product bryostatin 1 has demonstrated procognitive and antidepressant effects in animals and has been entered into human clinical trials for treating Alzheimer's disease (AD). The ability of bryostatin 1 to enhance learning and memory has largely been attributed to its effects on the structure and function of hippocampal neurons. However, relatively little is known about how bryostatin 1 influences the morphology of cortical neurons, key cells that also support learning and memory processes and are negatively impacted in AD. Here, we use a combination of carefully designed chemical probes and pharmacological inhibitors to establish that bryostatin 1 increases cortical synaptogenesis while decreasing dendritic spine density in a protein kinase C (PKC)-dependent manner. The effects of bryostatin 1 on cortical neurons are distinct from those induced by neural plasticity-promoting psychoplastogens such as ketamine. Compounds capable of increasing synaptic density with concomitant loss of immature dendritic spines may represent a unique pharmacological strategy for enhancing memory by improving signal-to-noise ratio in the central nervous system.
Collapse
Affiliation(s)
- Calvin Ly
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Akira J Shimizu
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305, United States
| | - Maxemiliano V Vargas
- Neuroscience Graduate Program, University of California, Davis, 1544 Newton Ct, Davis, California 95618, United States
| | - Whitney C Duim
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Paul A Wender
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305, United States.,Chemical and Systems Biology, Stanford University, 269 Campus Drive, Stanford, California 94305, United States
| | - David E Olson
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States.,Department of Biochemistry & Molecular Medicine, School of Medicine, University of California, Davis, 2700 Stockton Blvd, Suite 2102, Sacramento, California 95817, United States.,Center for Neuroscience, University of California, Davis, 1544 Newton Ct, Davis, California 95618, United States
| |
Collapse
|
7
|
Gamlin CR, Zhang C, Dyer MA, Wong ROL. Distinct Developmental Mechanisms Act Independently to Shape Biased Synaptic Divergence from an Inhibitory Neuron. Curr Biol 2020; 30:1258-1268.e2. [PMID: 32109390 DOI: 10.1016/j.cub.2020.01.080] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/19/2019] [Accepted: 01/28/2020] [Indexed: 12/19/2022]
Abstract
Neurons often contact more than one postsynaptic partner type and display stereotypic patterns of synaptic divergence. Such synaptic patterns usually involve some partners receiving more synapses than others. The developmental strategies generating "biased" synaptic distributions remain largely unknown. To gain insight, we took advantage of a compact circuit in the vertebrate retina, whereby the AII amacrine cell (AII AC) provides inhibition onto cone bipolar cell (BC) axons and retinal ganglion cell (RGC) dendrites, but makes the majority of its synapses with the BCs. Using light and electron microscopy, we reconstructed the morphology and connectivity of mouse retinal AII ACs across postnatal development. We found that AII ACs do not elaborate their presynaptic structures, the lobular appendages, until BCs differentiate about a week after RGCs are present. Lobular appendages are present in mutant mice lacking BCs, implying that although synchronized with BC axonal differentiation, presynaptic differentiation of the AII ACs is not dependent on cues from BCs. With maturation, AII ACs maintain a constant number of synapses with RGCs, preferentially increase synaptogenesis with BCs, and eliminate synapses with wide-field amacrine cells. Thus, AII ACs undergo partner type-specific changes in connectivity to attain their mature pattern of synaptic divergence. Moreover, AII ACs contact non-BCs to the same extent in bipolarless retinas, indicating that AII ACs establish partner-type-specific connectivity using diverse mechanisms that operate in parallel but independently.
Collapse
Affiliation(s)
- Clare R Gamlin
- Department of Biological Structure, University of Washington, NE Pacific Street, Seattle, WA 98195, USA
| | - Chi Zhang
- Department of Biological Structure, University of Washington, NE Pacific Street, Seattle, WA 98195, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude's Children Research Hospital, Danny Thomas Place, Memphis, TN 38105, USA
| | - Rachel O L Wong
- Department of Biological Structure, University of Washington, NE Pacific Street, Seattle, WA 98195, USA.
| |
Collapse
|
8
|
LRRTM4: A Novel Regulator of Presynaptic Inhibition and Ribbon Synapse Arrangements of Retinal Bipolar Cells. Neuron 2020; 105:1007-1017.e5. [PMID: 31974009 DOI: 10.1016/j.neuron.2019.12.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 10/17/2019] [Accepted: 12/23/2019] [Indexed: 12/16/2022]
Abstract
LRRTM4 is a transsynaptic adhesion protein regulating glutamatergic synapse assembly on dendrites of central neurons. In the mouse retina, we find that LRRTM4 is enriched at GABAergic synapses on axon terminals of rod bipolar cells (RBCs). Knockout of LRRTM4 reduces RBC axonal GABAA and GABAC receptor clustering and disrupts presynaptic inhibition onto RBC terminals. LRRTM4 removal also perturbs the stereotyped output synapse arrangement at RBC terminals. Synaptic ribbons are normally apposed to two distinct postsynaptic "dyad" partners, but in the absence of LRRTM4, "monad" and "triad" arrangements are also formed. RBCs from retinas deficient in GABA release also demonstrate dyad mis-arrangements but maintain LRRTM4 expression, suggesting that defects in dyad organization in the LRRTM4 knockout could originate from reduced GABA receptor function. LRRTM4 is thus a key synapse organizing molecule at RBC terminals, where it regulates function of GABAergic synapses and assembly of RBC synaptic dyads.
Collapse
|
9
|
Automated Macro Approach to Quantify Synapse Density in 2D Confocal Images from Fixed Immunolabeled Neural Tissue Sections. Methods Mol Biol 2019. [PMID: 31432476 DOI: 10.1007/978-1-4939-9686-5_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2023]
Abstract
This chapter describes an ImageJ/Fiji automated macro approach to estimate synapse densities in 2D fluorescence confocal microscopy images. The main step-by-step imaging workflow is explained, including example macro language scripts that perform all steps automatically for multiple images. Such tool provides a straightforward method for exploratory synapse screenings where hundreds to thousands of images need to be analyzed in order to render significant statistical information. The method can be adapted to any particular set of images where fixed brain slices have been immunolabeled against validated presynaptic and postsynaptic markers.
Collapse
|
10
|
Hartveit E, Zandt BJ, Madsen E, Castilho Á, Mørkve SH, Veruki ML. AMPA receptors at ribbon synapses in the mammalian retina: kinetic models and molecular identity. Brain Struct Funct 2017; 223:769-804. [PMID: 28936725 DOI: 10.1007/s00429-017-1520-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 09/10/2017] [Indexed: 10/24/2022]
Abstract
In chemical synapses, neurotransmitter molecules released from presynaptic vesicles activate populations of postsynaptic receptors that vary in functional properties depending on their subunit composition. Differential expression and localization of specific receptor subunits are thought to play fundamental roles in signal processing, but our understanding of how that expression is adapted to the signal processing in individual synapses and microcircuits is limited. At ribbon synapses, glutamate release is independent of action potentials and characterized by a high and rapidly changing rate of release. Adequately translating such presynaptic signals into postsynaptic electrical signals poses a considerable challenge for the receptor channels in these synapses. Here, we investigated the functional properties of AMPA receptors of AII amacrine cells in rat retina that receive input at spatially segregated ribbon synapses from OFF-cone and rod bipolar cells. Using patch-clamp recording from outside-out patches, we measured the concentration dependence of response amplitude and steady-state desensitization, the single-channel conductance and the maximum open probability. The GluA4 subunit seems critical for the functional properties of AMPA receptors in AII amacrines and immunocytochemical labeling suggested that GluA4 is located at synapses made by both OFF-cone bipolar cells and rod bipolar cells. Finally, we used a series of experimental observables to develop kinetic models for AII amacrine AMPA receptors and subsequently used the models to explore the behavior of the receptors and responses generated by glutamate concentration profiles mimicking those occurring in synapses. These models will facilitate future in silico modeling of synaptic signaling and processing in AII amacrine cells.
Collapse
Affiliation(s)
- Espen Hartveit
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Bas-Jan Zandt
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.,Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL), Geneva, Switzerland
| | - Eirik Madsen
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.,Department of Radiology, Førde Central Hospital, Førde, Norway
| | - Áurea Castilho
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
| | - Svein Harald Mørkve
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.,Department of Neurosurgery, Haukeland University Hospital, Bergen, Norway.,Department of Radiology, Haukeland University Hospital, Bergen, Norway
| | - Margaret Lin Veruki
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| |
Collapse
|