101
|
Mehta B, Snellman J, Chen S, Li W, Zenisek D. Synaptic ribbons influence the size and frequency of miniature-like evoked postsynaptic currents. Neuron 2013; 77:516-27. [PMID: 23395377 DOI: 10.1016/j.neuron.2012.11.024] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2012] [Indexed: 12/27/2022]
Abstract
Nonspiking cells of several sensory systems respond to stimuli with graded changes in neurotransmitter release and possess specialized synaptic ribbons. Here, we show that manipulations to synaptic ribbons caused dramatic effects on mEPSC-like (mlEPSC) amplitude and frequency. Damage to rod-bipolar cell ribbons using fluorophore-assisted light inactivation resulted in the immediate reduction of mlEPSC amplitude and frequency, whereas the first evoked response after damage remained largely intact. The reduction in amplitude could not be recovered by increasing release frequency after ribbon damage. In parallel experiments, we looked at mlEPSCs from cones of hibernating ground squirrels, which exhibit dramatically smaller ribbons than awake animals. Fewer and smaller mlEPSCs were observed postsynaptic to cones from hibernating animals, although depolarized cones were able to generate larger mlEPSCs. Our results indicate that ribbon size may influence mlEPSC frequency and support a role for ribbons in coordinating multivesicular release.
Collapse
Affiliation(s)
- Bhupesh Mehta
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, Sterling Hall of Medicine, Room B147, New Haven, CT 06520, USA
| | | | | | | | | |
Collapse
|
102
|
Kranz K, Paquet-Durand F, Weiler R, Janssen-Bienhold U, Dedek K. Testing for a gap junction-mediated bystander effect in retinitis pigmentosa: secondary cone death is not altered by deletion of connexin36 from cones. PLoS One 2013; 8:e57163. [PMID: 23468924 PMCID: PMC3584123 DOI: 10.1371/journal.pone.0057163] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 01/18/2013] [Indexed: 11/23/2022] Open
Abstract
Retinitis pigmentosa (RP) relates to a group of hereditary neurodegenerative diseases of the retina. On the cellular level, RP results in the primary death of rod photoreceptors, caused by rod-specific mutations, followed by a secondary degeneration of genetically normal cones. Different mechanisms may influence the spread of cell death from one photoreceptor type to the other. As one of these mechanisms a gap junction-mediated bystander effect was proposed, i.e., toxic molecules generated in dying rods and propagating through gap junctions induce the death of healthy cone photoreceptors. We investigated whether disruption of rod-cone coupling can prevent secondary cone death and reduce the spread of degeneration. We tested this hypothesis in two different mouse models for retinal degeneration (rhodopsin knockout and rd1) by crossbreeding them with connexin36-deficient mice as connexin36 represents the gap junction protein on the cone side and lack thereof most likely disrupts rod-cone coupling. Using immunohistochemistry, we compared the progress of cone degeneration between connexin36-deficient mouse mutants and their connexin36-expressing littermates at different ages and assessed the accompanied morphological changes during the onset (rhodopsin knockout) and later stages of secondary cone death (rd1 mutants). Connexin36-deficient mouse mutants showed the same time course of cone degeneration and the same morphological changes in second order neurons as their connexin36-expressing littermates. Thus, our results indicate that disruption of connexin36-mediated rod-cone coupling does not stop, delay or spatially restrict secondary cone degeneration and suggest that the gap junction-mediated bystander effect does not contribute to the progression of RP.
Collapse
Affiliation(s)
- Katharina Kranz
- Department of Neurobiology, University of Oldenburg, Oldenburg, Germany.
| | | | | | | | | |
Collapse
|
103
|
Völgyi B, Kovács-Oller T, Atlasz T, Wilhelm M, Gábriel R. Gap junctional coupling in the vertebrate retina: variations on one theme? Prog Retin Eye Res 2013; 34:1-18. [PMID: 23313713 DOI: 10.1016/j.preteyeres.2012.12.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/18/2012] [Accepted: 12/28/2012] [Indexed: 10/27/2022]
Abstract
Gap junctions connect cells in the bodies of all multicellular organisms, forming either homologous or heterologous (i.e. established between identical or different cell types, respectively) cell-to-cell contacts by utilizing identical (homotypic) or different (heterotypic) connexin protein subunits. Gap junctions in the nervous system serve electrical signaling between neurons, thus they are also called electrical synapses. Such electrical synapses are particularly abundant in the vertebrate retina where they are specialized to form links between neurons as well as glial cells. In this article, we summarize recent findings on retinal cell-to-cell coupling in different vertebrates and identify general features in the light of the evergrowing body of data. In particular, we describe and discuss tracer coupling patterns, connexin proteins, junctional conductances and modulatory processes. This multispecies comparison serves to point out that most features are remarkably conserved across the vertebrate classes, including (i) the cell types connected via electrical synapses; (ii) the connexin makeup and the conductance of each cell-to-cell contact; (iii) the probable function of each gap junction in retinal circuitry; (iv) the fact that gap junctions underlie both electrical and/or tracer coupling between glial cells. These pan-vertebrate features thus demonstrate that retinal gap junctions have changed little during the over 500 million years of vertebrate evolution. Therefore, the fundamental architecture of electrically coupled retinal circuits seems as old as the retina itself, indicating that gap junctions deeply incorporated in retinal wiring from the very beginning of the eye formation of vertebrates. In addition to hard wiring provided by fast synaptic transmitter-releasing neurons and soft wiring contributed by peptidergic, aminergic and purinergic systems, electrical coupling may serve as the 'skeleton' of lateral processing, enabling important functions such as signal averaging and synchronization.
Collapse
Affiliation(s)
- Béla Völgyi
- Department of Ophthalmology, School of Medicine, New York University, 550 First Avenue, MSB 149, New York, NY 10016, USA.
| | | | | | | | | |
Collapse
|
104
|
Role of melatonin and its receptors in the vertebrate retina. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 300:211-42. [PMID: 23273863 DOI: 10.1016/b978-0-12-405210-9.00006-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Melatonin is a chemical signal of darkness that is produced by retinal photoreceptors and pinealocytes. In the retina, melatonin diffuses from the photoreceptors to bind to specific receptors on a variety of inner retinal neurons to modify their activity. Potential target cells for melatonin in the inner retina are amacrine cells, bipolar cells, horizontal cells, and ganglion cells. Melatonin inhibits the release of dopamine from amacrine cells and increases the light sensitivity of horizontal cells. Melatonin receptor subtypes show differential, cell-specific patterns of expression that are likely to underlie differential functional modulation of specific retinal pathways. Melatonin potentiates rod signals to ON-type bipolar cells, via activation of the melatonin MT2 (Mel1b) receptor, suggesting that melatonin modulates the function of specific retinal circuits based on the differential distribution of its receptors. The selective and differential expression of melatonin receptor subtypes in cone circuits suggest a conserved function for melatonin in enhancing transmission from rods to second-order neurons and thus promote dark adaptation.
Collapse
|
105
|
|
106
|
Chen J, Sampath AP. Structure and Function of Rod and Cone Photoreceptors. Retina 2013. [DOI: 10.1016/b978-1-4557-0737-9.00014-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
107
|
Gollisch T. Features and functions of nonlinear spatial integration by retinal ganglion cells. ACTA ACUST UNITED AC 2012; 107:338-48. [PMID: 23262113 DOI: 10.1016/j.jphysparis.2012.12.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 11/19/2012] [Accepted: 12/04/2012] [Indexed: 11/27/2022]
Abstract
Ganglion cells in the vertebrate retina integrate visual information over their receptive fields. They do so by pooling presynaptic excitatory inputs from typically many bipolar cells, which themselves collect inputs from several photoreceptors. In addition, inhibitory interactions mediated by horizontal cells and amacrine cells modulate the structure of the receptive field. In many models, this spatial integration is assumed to occur in a linear fashion. Yet, it has long been known that spatial integration by retinal ganglion cells also incurs nonlinear phenomena. Moreover, several recent examples have shown that nonlinear spatial integration is tightly connected to specific visual functions performed by different types of retinal ganglion cells. This work discusses these advances in understanding the role of nonlinear spatial integration and reviews recent efforts to quantitatively study the nature and mechanisms underlying spatial nonlinearities. These new insights point towards a critical role of nonlinearities within ganglion cell receptive fields for capturing responses of the cells to natural and behaviorally relevant visual stimuli. In the long run, nonlinear phenomena of spatial integration may also prove important for implementing the actual neural code of retinal neurons when designing visual prostheses for the eye.
Collapse
Affiliation(s)
- Tim Gollisch
- University Medical Center Göttingen, Department of Ophthalmology, Waldweg 33, 37073 Göttingen, Germany.
| |
Collapse
|
108
|
Yang J, Pahng J, Wang GY. Dopamine modulates the off pathway in light-adapted mouse retina. J Neurosci Res 2012; 91:138-50. [PMID: 23023788 DOI: 10.1002/jnr.23137] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 07/24/2012] [Accepted: 08/02/2012] [Indexed: 11/10/2022]
Abstract
DL-2-Amino-4-phosphonobutyric acid (APB) is often used as a tool to block On pathways in studies of interactions between On and Off pathways in retinas. APB is an agonist of mGluR6 receptors and hyperpolarizes the On cone bipolar cells and rod bipolar cells. How APB affects Off responses of retinal ganglion cells (RGCs) in mouse retinas under dark and light adaptation is not clear. The light-evoked excitatory postsynaptic currents (light-evoked EPSCs) from Off and On-Off RGCs cells were recorded using whole-cell patch-clamp recording to assess how APB affects Off responses (light-evoked Off EPSCs) of RGCs in dark- and light-adapted mouse retinas. We found that APB differentially affected Off responses of RGCs in dark- and light-adapted mouse retinas. Under dark adaptation, while the APB-sensitive Off responses were blocked, APB increased the remaining Off responses (mainly from the secondary rod Off pathways) via removal of inhibition from On pathways to Off pathways. Under light adaptation, APB decreased Off responses. Glycinergic and GABAergic antagonists did not prevent the APB-induced reduction of Off responses of RGCs; however, a dopaminergic type 1 receptor (D(1)) blocker (SCH 23390) and a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker (ZD 7288) prevented the APB-induced reduction of Off responses of RGCs under light adaptation. The results indicated afunctional circuit: On cone bipolar cells to Off cone bipolar cells via D(1) receptors and HCN channels.
Collapse
Affiliation(s)
- Jinnan Yang
- Department of Structural and Cellular Biology, School of Medicine, Tulane University, New Orleans, Louisiana 70112, USA
| | | | | |
Collapse
|
109
|
Marc RE, Jones BW, Lauritzen JS, Watt CB, Anderson JR. Building retinal connectomes. Curr Opin Neurobiol 2012; 22:568-74. [PMID: 22498714 PMCID: PMC3415605 DOI: 10.1016/j.conb.2012.03.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 03/19/2012] [Accepted: 03/19/2012] [Indexed: 01/22/2023]
Abstract
Understanding vertebrate vision depends on knowing, in part, the complete network graph of at least one representative retina. Acquiring such graphs is the business of synaptic connectomics, emerging as a practical technology due to improvements in electron imaging platform control, management software for large-scale datasets, and availability of data storage. The optimal strategy for building complete connectomes uses transmission electron imaging with 2 nm or better resolution, molecular tags for cell identification, open-access data volumes for navigation, and annotation with open-source tools to build 3D cell libraries, complete network diagrams and connectivity databases. The first forays into retinal connectomics have shown that even nominally well-studied cells have much richer connection graphs than expected.
Collapse
Affiliation(s)
- Robert E. Marc
- University of Utah School of Medicine, Department of Ophthalmology / John A. Moran Eye Center, 65 Mario Capecchi Dr, Salt Lake City UT 84132
| | - Bryan W. Jones
- University of Utah School of Medicine, Department of Ophthalmology / John A. Moran Eye Center, 65 Mario Capecchi Dr, Salt Lake City UT 84132
| | - J. Scott Lauritzen
- University of Utah School of Medicine, Department of Ophthalmology / John A. Moran Eye Center, 65 Mario Capecchi Dr, Salt Lake City UT 84132
| | - Carl B. Watt
- University of Utah School of Medicine, Department of Ophthalmology / John A. Moran Eye Center, 65 Mario Capecchi Dr, Salt Lake City UT 84132
| | - James R. Anderson
- University of Utah School of Medicine, Department of Ophthalmology / John A. Moran Eye Center, 65 Mario Capecchi Dr, Salt Lake City UT 84132
| |
Collapse
|
110
|
Hartveit E, Veruki ML. Electrical synapses between AII amacrine cells in the retina: Function and modulation. Brain Res 2012; 1487:160-72. [PMID: 22776293 DOI: 10.1016/j.brainres.2012.05.060] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 05/09/2012] [Indexed: 12/24/2022]
Abstract
Adaptation enables the visual system to operate across a large range of background light intensities. There is evidence that one component of this adaptation is mediated by modulation of gap junctions functioning as electrical synapses, thereby tuning and functionally optimizing specific retinal microcircuits and pathways. The AII amacrine cell is an interneuron found in most mammalian retinas and plays a crucial role for processing visual signals in starlight, twilight and daylight. AII amacrine cells are connected to each other by gap junctions, potentially serving as a substrate for signal averaging and noise reduction, and there is evidence that the strength of electrical coupling is modulated by the level of background light. Whereas there is extensive knowledge concerning the retinal microcircuits that involve the AII amacrine cell, it is less clear which signaling pathways and intracellular transduction mechanisms are involved in modulating the junctional conductance between electrically coupled AII amacrine cells. Here we review the current state of knowledge, with a focus on the recent evidence that suggests that the modulatory control involves activity-dependent changes in the phosphorylation of the gap junction channels between AII amacrine cells, potentially linked to their intracellular Ca(2+) dynamics. This article is part of a Special Issue entitled Electrical Synapses.
Collapse
Affiliation(s)
- Espen Hartveit
- University of Bergen, Department of Biomedicine, Bergen, Norway.
| | | |
Collapse
|
111
|
Abstract
Amacrine cells represent the most diverse class of retinal neuron, comprising dozens of distinct cell types. Each type exhibits a unique morphology and generates specific visual computations through its synapses with a subset of excitatory interneurons (bipolar cells), other amacrine cells, and output neurons (ganglion cells). Here, we review the intrinsic and network properties that underlie the function of the most common amacrine cell in the mammalian retina, the AII amacrine cell. The AII connects rod and cone photoreceptor pathways, forming an essential link in the circuit for rod-mediated (scotopic) vision. As such, the AII has become known as the rod-amacrine cell. We, however, now understand that AII function extends to cone-mediated (photopic) vision, and AII function in scotopic and photopic conditions utilizes the same underlying circuit: AIIs are electrically coupled to each other and to the terminals of some types of ON cone bipolar cells. The direction of signal flow, however, varies with illumination. Under photopic conditions, the AII network constitutes a crossover inhibition pathway that allows ON signals to inhibit OFF ganglion cells and contributes to motion sensitivity in certain ganglion cell types. We discuss how the AII's combination of intrinsic and network properties accounts for its unique role in visual processing.
Collapse
|
112
|
Abstract
Amacrine cells are a morphologically and functionally diverse group of inhibitory interneurons. Morphologically, they have been divided into approximately 30 types. Although this diversity is probably important to the fine structure and function of the retinal circuit, the amacrine cells have been more generally divided into two subclasses. Glycinergic narrow-field amacrine cells have dendrites that ramify close to their somas, cross the sublaminae of the inner plexiform layer, and create cross talk between its parallel ON and OFF pathways. GABAergic wide-field amacrine cells have dendrites that stretch long distances from their soma but ramify narrowly within an inner plexiform layer sublamina. These wide-field cells are thought to mediate inhibition within a sublamina and thus within the ON or OFF pathway. The postsynaptic targets of all amacrine cell types include bipolar, ganglion, and other amacrine cells. Almost all amacrine cells use GABA or glycine as their primary neurotransmitter, and their postsynaptic receptor targets include the most common GABA(A), GABA(C), and glycine subunit receptor configurations. This review addresses the diversity of amacrine cells, the postsynaptic receptors on their target cells in the inner plexiform layer of the retina, and some of the inhibitory mechanisms that arise as a result. When possible, the effects of GABAergic and glycinergic inputs on the visually evoked responses of their postsynaptic targets are discussed.
Collapse
|
113
|
Cangiano L, Asteriti S, Cervetto L, Gargini C. The photovoltage of rods and cones in the dark-adapted mouse retina. J Physiol 2012; 590:3841-55. [PMID: 22641773 DOI: 10.1113/jphysiol.2011.226878] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Research on photoreceptors has led to important insights into how light signals are detected and processed in the outer retina. Most information about photoreceptor function, however, comes from lower vertebrates. The large majority of mammalian studies are based on suction pipette recordings of outer segment currents, a technique that doesn't allow examination of phenomena occurring downstream of phototransduction. Only a small number of whole-cell recordings have been made, mainly in the macaque. Due to the growing importance of the mouse in vision research, we have optimized a retinal slice preparation that allows the reliable collection of perforated-patch recordings from light responding rods and cones. Unexpectedly, the frequency of cone recordings was much higher than their numeric proportion of ∼3%. This allowed us to obtain direct functional evidence suggestive of rod–cone coupling in the mouse. Moreover, rods had considerably larger single photon responses than previously published for mammals (3.44 mV, SD 1.37, n = 19 at 24°C; 2.46 mV, SD 1.08, n = 10 at 36°C), and a relatively high signal/noise ratio (6.4, SD 1.8 at 24°C; 6.8, SD 2.8 at 36°C). Both findings imply a more favourable transmission at the rod–rod bipolar cell synapse. Accordingly, relatively few photoisomerizations were sufficient to elicit a half-maximal response (6.7, SD 2.7, n = 5 at 24°C; 10.6, SD 1.7, n = 3 at 36°C), leading to a narrow linear response range. Our study demonstrates new features of mammalian photoreceptors and opens the way for further investigations into photoreceptor function using retinas from mutant mouse models.
Collapse
Affiliation(s)
- Lorenzo Cangiano
- Department of Physiological Sciences, University of Pisa, Via San Zeno 31, I-56123 Pisa, Italy.
| | | | | | | |
Collapse
|
114
|
Abstract
Vision is the most important of the senses for humans, and the retina is the first stage in the processing of light signals in the visual system. In the retina, highly specialized light-sensing neurons, the rod and cone photoreceptors, convert light into neural signals. These signals are extensively processed and filtered in the subsequent retinal network before transmitted to the higher visual centres in the brain, where the perception of viewed objects and scenes is finally constructed. A key feature of signal processing in the mammalian retina is parallel processing. Visual information is segregated in parallel pathways already at the rod and cone photoreceptor terminals, which provide multiple output synapses for the faithful encoding and transfer of the visual signals to the post-receptoral retinal network. This review aims at highlighting the current knowledge about the structural and functional pre- and post-synaptic specializations of rod and cone photoreceptor ribbon synapses, which belong to the most complex chemical synapses in the central nervous system.
Collapse
Affiliation(s)
- H Regus-Leidig
- Animal Physiology, Department of Biology, University of Erlangen-Nuremberg, Germany
| | | |
Collapse
|
115
|
Puthussery T, Gayet-Primo J, Taylor WR, Haverkamp S. Immunohistochemical identification and synaptic inputs to the diffuse bipolar cell type DB1 in macaque retina. J Comp Neurol 2012; 519:3640-56. [PMID: 22006647 DOI: 10.1002/cne.22756] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detailed analysis of the synaptic inputs to the primate DB1 bipolar cell has been precluded by the absence of a suitable immunohistochemical marker. Here we demonstrate that antibodies for the EF-hand calcium-binding protein, secretagogin, strongly label the DB1 bipolar cell as well as a mixed population of GABAergic amacrine cells in the macaque retina. Using secretagogin as a marker, we show that the DB1 bipolar makes synaptic contact with both L/M as well as S-cone photoreceptors and only minimal contact with rod photoreceptors. Electron microscopy showed that the DB1 bipolar makes flat contacts at both triad-associated and nontriad-associated positions on the cone pedicle. Double labeling with various glutamate receptor subunit antibodies failed to conclusively determine the subunit composition of the glutamate receptors on DB1 bipolar cells. In the IPL, DB1 bipolar cell axon terminals expressed the glycine receptor, GlyRα1, at sites of contact with AII amacrine cells, suggesting that these cells receive input from the rod pathway.
Collapse
Affiliation(s)
- Theresa Puthussery
- Casey Eye Institute, Department of Ophthalmology, Oregon Health and Sciences University, Portland, Oregon 97239, USA.
| | | | | | | |
Collapse
|
116
|
Shi Z, Jervis D, Nickerson PEB, Chow RL. Requirement for the paired-like homeodomain transcription factor VSX1 in type 3a mouse retinal bipolar cell terminal differentiation. J Comp Neurol 2012; 520:117-29. [PMID: 21674500 DOI: 10.1002/cne.22697] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Retinal bipolar cells make up a class of at least 11 distinct interneurons that have been classified through morphological and molecular approaches. Previous work has shown that the paired-like homeodomain transcription factor Vsx1 is essential for the proper development of a subset of these interneurons. In Vsx1-null mice, bipolar cells are properly specified but exhibit terminal differentiation defects characterized by reduced expression of OFF bipolar cell markers and defects in OFF visual signaling. Here, we further examined the role of Vsx1 in OFF bipolar cells using recently identified cell-type-specific markers. In contrast to its previously characterized expression in type 2 OFF bipolar cells, Vsx1 expression was not detected in type 3 OFF bipolar cells, by either immunohistological or transgenic reporter labeling approaches. This observation was unexpected given previous findings that Cabp5 immunolabeling of type 3 bipolar cell axon terminals is reduced in Vsx1-null mice. However, we observed reduced levels of the type 3a bipolar cell marker hyperpolarization-activated and cyclic nucleotide-gated channel 4 (HCN4) in Vsx1-null mice, which is consistent with a requirement for Vsx1 in type 3 bipolar cell differentiation. In contrast, expression of the type 3b bipolar cell marker regulatory subunit RII-beta of protein kinase A was unchanged. Despite the absence of Vsx1 in mature type 3 bipolar cells, colabeling of Vsx1 and HCN4 was observed at postnatal stages. These findings reveal a role for Vsx1 in type 3a bipolar cells and suggest that Vsx1 function is required transiently in this cell type during the postnatal period.
Collapse
Affiliation(s)
- Zhiwei Shi
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | | | | | | |
Collapse
|
117
|
Pang JJ, Gao F, Paul DL, Wu SM. Rod, M-cone and M/S-cone inputs to hyperpolarizing bipolar cells in the mouse retina. J Physiol 2012; 590:845-54. [PMID: 22219344 PMCID: PMC3381314 DOI: 10.1113/jphysiol.2011.224113] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2011] [Accepted: 12/27/2011] [Indexed: 11/08/2022] Open
Abstract
Bipolar cells are the central neurons of the retina that convey visual signals from rod and cone photoreceptors in the outer retina to higher-order neurons in the inner retina and the brain. Early anatomical studies have suggested that there are four types of cone hyperpolarizing (OFF) bipolar cells (HBCs) in the mouse retina, but no light responses have been systematically examined. By analysing light-evoked cation and chloride currents (I(C) and I(Cl)) from over 50 morphologically identified HBCs in the dark-adapted wildtype and connexin36 knockout (Cx36(-/-)) mouse retinas, we identified three types of HBCs, each with distinct light responses and morphological characteristics. The HBC(R/MC)s with axon terminals ramifying between 0% and 30% of the inner plexiform layer (IPL) receive mixed inputs from rods and M-cones, the HBC(MC)s with axon terminals ramifying between 10% and 50% of the IPL receive inputs primarily from M-cones, and the HBC(M/SC)s with axon terminals ramifying between 25% and 50% of IPL receive inputs primarily from cones with mixed M- and S-cone pigments. Moreover, we found that HBC(R/MC)s in the Cx36(-/-) mice exhibit light responses very similar to the wildtype HBC(R/MC)s, suggesting that the mixed rod-cone inputs are not mediated by connexin36-dependent rod-cone coupling, but rather by direct synaptic contacts from rods and M-cones. This study constitutes the first systematic investigation that correlates light response characteristics and axonal morphology of HBCs in dark-adapted mouse retina, and contributes to recently emerging evidence that revises the traditional view that mammalian HBCs only contact cone photoreceptors.
Collapse
Affiliation(s)
- Ji-Jie Pang
- Cullen Eye Institute, Baylor College of Medicine, One Baylor Plaza, NC-205, Houston, TX 77030, USA
| | | | | | | |
Collapse
|
118
|
Arman AC, Sampath AP. Dark-adapted response threshold of OFF ganglion cells is not set by OFF bipolar cells in the mouse retina. J Neurophysiol 2012; 107:2649-59. [PMID: 22338022 DOI: 10.1152/jn.01202.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nervous system frequently integrates parallel streams of information to encode a broad range of stimulus strengths. In mammalian retina it is generally believed that signals generated by rod and cone photoreceptors converge onto cone bipolar cells prior to reaching the retinal output, the ganglion cells. Near absolute visual threshold a specialized mammalian retinal circuit, the rod bipolar pathway, pools signals from many rods and converges on depolarizing (AII) amacrine cells. However, whether subsequent signal flow to OFF ganglion cells requires OFF cone bipolar cells near visual threshold remains unclear. Glycinergic synapses between AII amacrine cells and OFF cone bipolar cells are believed to relay subsequently rod-driven signals to OFF ganglion cells. However, AII amacrine cells also make glycinergic synapses directly with OFF ganglion cells. To determine the route for signal flow near visual threshold, we measured the effect of the glycine receptor antagonist strychnine on response threshold in fully dark-adapted retinal cells. As shown previously, we found that response threshold for OFF ganglion cells was elevated by strychnine. Surprisingly, strychnine did not elevate response threshold in any subclass of OFF cone bipolar cell. Instead, in every OFF cone bipolar subclass strychnine suppressed tonic glycinergic inhibition without altering response threshold. Consistent with this lack of influence of strychnine, we found that the dominant input to OFF cone bipolar cells in darkness was excitatory and the response threshold of the excitatory input varied by subclass. Thus, in the dark-adapted mouse retina, the high absolute sensitivity of OFF ganglion cells cannot be explained by signal transmission through OFF cone bipolar cells.
Collapse
Affiliation(s)
- A Cyrus Arman
- Neurosciences Graduate Program, Department of Physiology and Biophysics, USC Keck School of Medicine, Los Angeles, CA, USA
| | | |
Collapse
|
119
|
Cembrowski MS, Logan SM, Tian M, Jia L, Li W, Kath WL, Riecke H, Singer JH. The mechanisms of repetitive spike generation in an axonless retinal interneuron. Cell Rep 2012; 1:155-66. [PMID: 22832164 DOI: 10.1016/j.celrep.2011.12.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 12/14/2011] [Accepted: 12/21/2011] [Indexed: 11/19/2022] Open
Abstract
Several types of retinal interneurons exhibit spikes but lack axons. One such neuron is the AII amacrine cell, in which spikes recorded at the soma exhibit small amplitudes (<10 mV) and broad time courses (>5 ms). Here, we used electrophysiological recordings and computational analysis to examine the mechanisms underlying this atypical spiking. We found that somatic spikes likely represent large, brief action potential-like events initiated in a single, electrotonically distal dendritic compartment. In this same compartment, spiking undergoes slow modulation, likely by an M-type K conductance. The structural correlate of this compartment is a thin neurite that extends from the primary dendritic tree: local application of TTX to this neurite, or excision of it, eliminates spiking. Thus, the physiology of the axonless AII is much more complex than would be anticipated from morphological descriptions and somatic recordings; in particular, the AII possesses a single dendritic structure that controls its firing pattern.
Collapse
Affiliation(s)
- Mark S Cembrowski
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA.
| | | | | | | | | | | | | | | |
Collapse
|
120
|
Abstract
AbstractFeedback is a ubiquitous feature of neural circuits in the mammalian central nervous system (CNS). Analogous to pure electronic circuits, neuronal feedback provides either a positive or negative influence on the output of upstream components/neurons. Although the particulars (i.e., connectivity, physiological encoding/processing/signaling) of circuits in higher areas of the brain are often unclear, the inner retina proves an excellent model for studying both the anatomy and physiology of feedback circuits within the functional context of visual processing. Inner retinal feedback to bipolar cells is almost entirely mediated by a single class of interneurons, the amacrine cells. Although this might sound like a simple circuit arrangement with an equally simple function, anatomical, molecular, and functional evidence suggest that amacrine cells represent an extremely diverse class of CNS interneurons that contribute to a variety of retinal processes. In this review, I classify the amacrine cells according to their anatomical output synapses and target cell(s) (i.e., bipolar cells, ganglion cells, and/or amacrine cells) and discuss specifically our current understandings of amacrine cell-mediated feedback and output to bipolar cells on the synaptic, cellular, and circuit levels, while drawing connections to visual processing.
Collapse
|
121
|
Pang JJ, Gao F, Wu SM. Physiological characterization and functional heterogeneity of narrow-field mammalian amacrine cells. J Physiol 2011; 590:223-34. [PMID: 22083601 DOI: 10.1113/jphysiol.2011.222141] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Light-evoked responses of 106 morphologically identified narrow-field amacrine cells (ACs) were studied in dark-adapted mouse retinal slices. Forty-five cells exhibit AIIAC morphology, 55% of which show characteristic AIIAC physiological properties (AIIAC1s) and the remaining 45% display different physiological responses, suggesting that AIIACs are functionally heterogeneous. Moreover, we found that 42 cells exhibit morphology that resembles the seven morphological types of glycine-positive ACs (GlyAC1-7) reported in the rat retina, and for the first time assigned light response and function properties to these morphological types of glycinergic ACs in the mouse retina. In addition, five narrow-field ACs exhibited morphology resembling that of the GlyAC5 or GlyAC7 but with different physiological responses (GlyAC5(#) and GlyAC7(#)). Therefore, the eight morphological types of narrow-field ACs exhibit 12 classes of physiological responses. Furthermore, we found ACs whose physiological responses were indistinguishable from those of GlyAC3 or GlyAC4s but with different morphology (GlyAC3* or GlyAC4*). These observations suggest that although the majority of narrow-field mammalian ACs forms discrete functional groups that correlate with their morphology, a significant number of these cells with similar morphology do not display the same light responses, and some with similar light responses do not exhibit the same morphology.
Collapse
Affiliation(s)
- Ji-Jie Pang
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | |
Collapse
|
122
|
Modulation of rod photoreceptor output by HCN1 channels is essential for regular mesopic cone vision. Nat Commun 2011; 2:532. [PMID: 22068599 DOI: 10.1038/ncomms1540] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 10/10/2011] [Indexed: 11/08/2022] Open
Abstract
Retinal photoreceptors permit visual perception over a wide range of lighting conditions. Rods work best in dim, and cones in bright environments, with considerable functional overlap at intermediate (mesopic) light levels. At many sites in the outer and inner retina where rod and cone signals interact, gap junctions, particularly those containing Connexin36, have been identified. However, little is known about the dynamic processes associated with the convergence of rod and cone system signals into ON- and OFF-pathways. Here we show that proper cone vision under mesopic conditions requires rapid adaptational feedback modulation of rod output via hyperpolarization-activated and cyclic nucleotide-gated channels 1. When these channels are absent, sustained rod responses following bright light exposure saturate the retinal network, resulting in a loss of downstream cone signalling. By specific genetic and pharmacological ablation of key signal processing components, regular cone signalling can be restored, thereby identifying the sites involved in functional rod-cone interactions.
Collapse
|
123
|
Freeman DK, Jeng JS, Kelly SK, Hartveit E, Fried SI. Calcium channel dynamics limit synaptic release in response to prosthetic stimulation with sinusoidal waveforms. J Neural Eng 2011; 8:046005. [PMID: 21628768 PMCID: PMC3152377 DOI: 10.1088/1741-2560/8/4/046005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Extracellular electric stimulation with sinusoidal waveforms has been shown to allow preferential activation of individual types of retinal neurons by varying stimulus frequency. It is important to understand the mechanisms underlying this frequency dependence as a step toward improving methods of preferential activation. In order to elucidate these mechanisms, we implemented a morphologically realistic model of a retinal bipolar cell and measured the response to extracellular stimulation with sinusoidal waveforms. We compared the frequency response of a passive membrane model to the kinetics of voltage-gated calcium channels that mediate synaptic release. The passive electrical properties of the membrane exhibited lowpass filtering with a relatively high cutoff frequency (nominal value = 717 Hz). This cutoff frequency was dependent on intra-axonal resistance, with shorter and wider axons yielding higher cutoff frequencies. However, we found that the cutoff frequency of bipolar cell synaptic release was primarily limited by the relatively slow opening kinetics of L- and T-type calcium channels. The cutoff frequency of calcium currents depended nonlinearly on stimulus amplitude, but remained lower than the cutoff frequency of the passive membrane model for a large range of membrane potential fluctuations. These results suggest that while it may be possible to modulate the membrane potential of bipolar cells over a wide range of stimulus frequencies, synaptic release will only be initiated at the lower end of this range.
Collapse
Affiliation(s)
- Daniel K Freeman
- Center for Innovative Visual Rehabilitation, Boston VA Healthcare System, 150 South Huntington Ave, Boston, MA 02130, USA
| | | | | | | | | |
Collapse
|
124
|
Acute destruction of the synaptic ribbon reveals a role for the ribbon in vesicle priming. Nat Neurosci 2011; 14:1135-41. [PMID: 21785435 PMCID: PMC3171202 DOI: 10.1038/nn.2870] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 05/25/2011] [Indexed: 11/08/2022]
Abstract
In vision, balance and hearing, sensory receptor cells translate sensory stimuli into electrical signals whose amplitude is graded with stimulus intensity. The output synapses of these sensory neurons must provide fast signaling to follow rapidly changing stimuli while also transmitting graded information covering a wide range of stimulus intensity and must be able to sustain this signaling for long time periods. To meet these demands, specialized machinery for transmitter release, the synaptic ribbon, has evolved at the synaptic outputs of these neurons. We found that acute disruption of synaptic ribbons by photodamage to the ribbon markedly reduced both sustained and transient components of neurotransmitter release in mouse bipolar cells and salamander cones without affecting the ultrastructure of the ribbon or its ability to localize synaptic vesicles to the active zone. Our results indicate that ribbons mediate both slow and fast signaling at sensory synapses and support an additional role for the synaptic ribbon in priming vesicles for exocytosis at active zones.
Collapse
|
125
|
Pahlberg J, Sampath AP. Visual threshold is set by linear and nonlinear mechanisms in the retina that mitigate noise: how neural circuits in the retina improve the signal-to-noise ratio of the single-photon response. Bioessays 2011; 33:438-47. [PMID: 21472740 DOI: 10.1002/bies.201100014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In sensory biology, a major outstanding question is how sensory receptor cells minimize noise while maximizing signal to set the detection threshold. This optimization could be problematic because the origin of both the signals and the limiting noise in most sensory systems is believed to lie in stimulus transduction. Signal processing in receptor cells can improve the signal-to-noise ratio. However, neural circuits can further optimize the detection threshold by pooling signals from sensory receptor cells and processing them using a combination of linear and nonlinear filtering mechanisms. In the visual system, noise limiting light detection has been assumed to arise from stimulus transduction in rod photoreceptors. In this context, the evolutionary optimization of the signal-to-noise ratio in the retina has proven critical in allowing visual sensitivity to approach the limits set by the quantal nature of light. Here, we discuss how noise in the mammalian retina is mitigated to allow for highly sensitive night vision.
Collapse
Affiliation(s)
- Johan Pahlberg
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA, USA.
| | | |
Collapse
|
126
|
Heikkinen H, Vinberg F, Nymark S, Koskelainen A. Mesopic background lights enhance dark-adapted cone ERG flash responses in the intact mouse retina: a possible role for gap junctional decoupling. J Neurophysiol 2011; 105:2309-18. [PMID: 21389302 DOI: 10.1152/jn.00536.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The cone-driven flash responses of mouse electroretinogram (ERG) increase as much as twofold over the course of several minutes during adaptation to a rod-compressing background light. The origins of this phenomenon were investigated in the present work by recording preflash-isolated (M-)cone flash responses ex vivo in darkness and during application of various steady background lights. In this protocol, the cone stimulating flash was preceded by a preflash that maintains rods under saturation (hyperpolarized) to allow selective stimulation of the cones at varying background light levels. The light-induced growth was found to represent true enhancement of cone flash responses with respect to their dark-adapted state. It developed within minutes, and its overall magnitude was a graded function of the background light intensity. The threshold intensity of cone response growth was observed with lights in the low mesopic luminance region, at which rod responses are partly compressed. Maximal effect was reached at intensities sufficient to suppress ∼ 90% of the rod responses. Light-induced enhancement of the cone photoresponses was not sensitive to antagonists and agonists of glutamatergic transmission. However, applying gap junction blockers to the dark-adapted retina produced qualitatively similar changes in the cone flash responses as did background light and prevented further growth during subsequent light-adaptation. These results are consistent with the idea that cone ERG photoresponses are suppressed in the dark-adapted mouse retina by gap junctional coupling between rods and cones. This coupling would then be gradually and reversibly removed by mesopic background lights, allowing larger functional range for the cone light responses.
Collapse
Affiliation(s)
- H Heikkinen
- Aalto University School of Science, Department of Biomedical Engineering and Computational Science, PO Box 12200, FI-00076 Aalto, Finland.
| | | | | | | |
Collapse
|
127
|
Brown TM, Allen AE, Wynne J, Paul DL, Piggins HD, Lucas RJ. Visual responses in the lateral geniculate evoked by Cx36-independent rod pathways. Vision Res 2011; 51:280-7. [PMID: 20709095 PMCID: PMC3741614 DOI: 10.1016/j.visres.2010.08.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 08/09/2010] [Accepted: 08/09/2010] [Indexed: 11/26/2022]
Abstract
Emerging evidence indicates rods can communicate with retinal ganglion cells (RGCs) via pathways that do not involve gap-junctions. Here we investigated the significance of such pathways for central visual responses, using mice lacking a key gap junction protein (Cx36(-/-)) and carrying a mutation that disrupts cone phototransduction (Gnat2(cpfl3)). Electrophysiological recordings spanning the lateral geniculate revealed rod-mediated ON and OFF visual responses in virtually every cell from all major anatomical sub-compartments of this nucleus. Hence, we demonstrate that one or more classes of RGC receive input from Cx36-independent rod pathways and drive extensive ON and OFF responses across the visual thalamus.
Collapse
Affiliation(s)
- Timothy M Brown
- Faculty of Life Sciences, University of Manchester, Manchester, UK.
| | | | | | | | | | | |
Collapse
|
128
|
Abstract
PURPOSE To investigate changes in cytokine levels in tears of type 2 diabetics with or without retinopathy. METHODS Tears were collected from 15 type 2 diabetics without retinopathy (DNR), 15 patients with retinopathy (DR), and 15 age and gender matched non-diabetic controls. Tear concentrations of 27 cytokines were measured by multiplex bead immunoassay. Cytokine differences between groups, ratios of type-1 T helper (Th1)/type-2 T helper (Th2) cytokines and anti-angiogenic/pro-angiogenic cytokines were analyzed statistically. RESULTS The most abundant cytokine detected in tears was interferon-induced protein-10 (IP-10). In comparison with controls, IP-10 and monocyte chemoattracant protein-1 (MCP-1) levels were significantly elevated in DR (p=0.016 and 0.036, respectively) and DNR groups (p=0.021 and 0.026, respectively). Interleukin-1 (IL-1) receptor antagonist (IL-1ra) levels were significantly increased in DNR (p=0.016). Th1/Th2 cytokines interferon-gamma (IFN-γ)/IL-5 and IL-2/IL-5 ratios were significantly increased in DR compared to controls (p=0.037 and 0.031, respectively). Anti-angiogenic/angiogenic cytokines IFN-γ/MCP-1 and IL-4/MCP-1 ratios in DR and DNR were significantly decreased compared to controls (p<0.05). IL-4/IL-8 and IL-12p70/IL-8 ratios were also significantly decreased in DR compared to controls (p=0.02 and 0.045, respectively). No significant correlation was demonstrated between tear cytokine concentrations and glycosylated hemoglobin (HbA1c) or fasting plasma glucose (FPG). CONCLUSIONS Diabetic tears exhibited elevated levels of IP-10 and MCP-1. The Th1/Th2 cytokine balance may shift to a predominantly Th1 state in DR patients. Pro-angiogenic cytokines are more highly represented than anti-angiogenic cytokines in the tears of diabetic patients.
Collapse
|
129
|
Abstract
In the retina, rod bipolar (RBP) cells synapse with many rods, and suppression of rod outer segment and synaptic noise is necessary for their detection of rod single-photon responses (SPRs). Depending on the rods' signal-to-noise ratio (SNR), the suppression mechanism will likely eliminate some SPRs as well, resulting in decreased quantum efficiency. We examined this synapse in rabbit, where 100 rods converge onto each RBP. Suction electrode recordings showed that rabbit rod SPRs were difficult to distinguish from noise (independent SNR estimates were 2.3 and 2.8). Nonlinear transmission from rods to RBPs improved response detection (SNR = 8.7), but a large portion of the rod SPRs was discarded. For the dimmest flashes, the loss approached 90%. Despite the high rejection ratio, noise of two distinct types was apparent in the RBP traces: low-amplitude rumblings and discrete events that resembled the SPR. The SPR-like event frequency suggests that they result from thermal isomerizations of rhodopsin, which occurred at the rate 0.033/s/rod. The presence of low-amplitude noise is explained by a sigmoidal input-output relationship at the rod-RBP synapse and the input of noisy rods. The rabbit rod SNR and RBP quantum efficiency are the lowest yet reported, suggesting that the quantum efficiency of the rod-RBP synapse may depend on the SNR in rods. These results point to the possibility that fewer photoisomerizations are discarded for species such as primate, which has a higher rod SNR.
Collapse
|
130
|
Abstract
The general principles of retinal organization are now well known. It may seem surprising that retinal organization in the primate, which has a complex visual behavioral repertoire, appears relatively simple. In this review, we primarily consider retinal structure and function in primate species. Photoreceptor distribution and connectivity are considered as are connectivity in the outer and inner retina. One key issue is the specificity of retinal connections; we suggest that the retina shows connectional specificity but this is seldom complete, and we consider here the functional consequences of imprecise wiring. Finally, we consider how retinal systems can be linked to psychophysical descriptions of different channels, chromatic and luminance, which are proposed to exist in the primate visual system.
Collapse
Affiliation(s)
- Barry B Lee
- SUNY College of Optometry, New York 10036, USA.
| | | | | |
Collapse
|
131
|
Bergholz R, Staks T, Rüther K. Effects of the AMPA antagonist ZK 200775 on visual function: a randomized controlled trial. PLoS One 2010; 5:e12111. [PMID: 20711429 PMCID: PMC2920815 DOI: 10.1371/journal.pone.0012111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Accepted: 06/10/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND ZK 200775 is an antagonist at the alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor and had earned attention as a possible neuroprotective agent in cerebral ischemia. Probands receiving the agent within phase I trials reported on an alteration of visual perception. In this trial, the effects of ZK 200775 on the visual system were analyzed in detail. METHODOLOGY In a randomised controlled trial we examined eyes and vision before and after the intravenous administration of two different doses of ZK 200775 and placebo. There were 3 groups of 6 probands each: Group 1 recieved 0.03 mg/kg/h, group 2 0.75 mg/kg/h of ZK 200775, the control group received 0.9% sodium chloride solution. Probands were healthy males aged between 57 and 69 years. The following methods were applied: clinical examination, visual acuity, ophthalmoscopy, colour vision, rod absolute threshold, central visual field, pattern-reversal visual evoked potentials (pVEP), ON-OFF and full-field electroretinogram (ERG). PRINCIPAL FINDINGS No effect of ZK 200775 was seen on eye position or motility, stereopsis, pupillary function or central visual field testing. Visual acuity and dark vision deteriorated significantly in both treated groups. Color vision was most remarkably impaired. The dark-adapted ERG revealed a reduction of oscillatory potentials (OP) and partly of the a- and b-wave, furthermore an alteration of b-wave morphology and an insignificantly elevated b/a-ratio. Cone-ERG modalities showed decreased amplitudes and delayed implicit times. In the ON-OFF ERG the ON-answer amplitudes increased whereas the peak times of the OFF-answer were reduced. The pattern VEP exhibited lower amplitudes and prolonged peak times. CONCLUSIONS The AMPA receptor blockade led to a strong impairment of typical OFF-pathway functions like color vision and the cone ERG. On the other hand the ON-pathway as measured by dark vision and the scotopic ERG was affected as well. This further elucidates the interdependence of both pathways. TRIAL REGISTRATION ClinicalTrials.gov NCT00999284.
Collapse
Affiliation(s)
- Richard Bergholz
- Department of Ophthalmology, Charité Universitätsmedizin Berlin, Campus Virchow-Klinikum, Berlin, Germany.
| | | | | |
Collapse
|
132
|
Okawa H, Miyagishima KJ, Arman AC, Hurley JB, Field GD, Sampath AP. Optimal processing of photoreceptor signals is required to maximize behavioural sensitivity. J Physiol 2010; 588:1947-60. [PMID: 20403975 DOI: 10.1113/jphysiol.2010.188573] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The sensitivity of receptor cells places a fundamental limit upon the sensitivity of sensory systems. For example, the signal-to-noise ratio of sensory receptors has been suggested to limit absolute thresholds in the visual and auditory systems. However, the necessity of optimally processing sensory receptor signals for behaviour to approach this limit has received less attention. We investigated the behavioural consequences of increasing the signal-to-noise ratio of the rod photoreceptor single-photon response in a transgenic mouse, the GCAPs-/- knockout. The loss of fast Ca2+ feedback to cGMP synthesis in phototransduction for GCAPs-/- mice increases the magnitude of the rod single-photon response and dark noise, with the increase in size of the single-photon response outweighing the increase in noise. Surprisingly, despite the increased rod signal-to-noise ratio, behavioural performance for GCAPs-/- mice was diminished near absolute visual threshold. We demonstrate in electrophysiological recordings that the diminished performance compared to wild-type mice is explained by poorly tuned postsynaptic processing of the rod single-photon response at the rod bipolar cell. In particular, the level of postsynaptic saturation in GCAPs-/- rod bipolar cells is not sufficient to eliminate rod noise, and degrades the single-photon response signal-to-noise ratio. Thus, it is critical for retinal processing to be optimally tuned near absolute threshold; otherwise the visual system fails to utilize fully the signals present in the rods.
Collapse
Affiliation(s)
- Haruhisa Okawa
- Department of Physiology and Biophysics, University of Southern California, USC Keck School of Medicine, 1501 San Pablo St, ZNI 435, Los Angeles, CA 90089, USA
| | | | | | | | | | | |
Collapse
|
133
|
Abstract
An open issue of retinal organization and function is the comprehension of the different tasks specifically performed by bipolar cells, the neurons that collect information from photoreceptors in the outer retina and convey the signal to the inner plexiform layer. Particularly interesting is to understand the unique contribution to the visual signal brought by cone bipolar cells, neurons typical of the mammalian retina and especially dedicated to receive synaptic input from cones. In all the species studied so far, it has been shown that cone bipolar cells occur in about ten different types, which form distinct clusters identified with a panel of both classical and modern genetic methods. Reviewed here is current literature illustrating the occurrence of morphological, molecular and architectural features that confer to each bipolar cell type exclusive fingerprints, ultimately predicting the emergence of similarly unique, albeit still partially unraveled, functional properties. Thus, differences among cone bipolar cells lay the ground for the genesis in the outer retina of parallel channels, which convey to the inner retina separate information, among others, about contrast, chromatic features and temporal properties of the visual signal.
Collapse
Affiliation(s)
- Enrica Strettoi
- CNR Neuroscience Institute, Area della Ricerca CNR, Via Giuseppe Moruzzi 1, 56100 Pisa, Italy.
| | | | | | | | | |
Collapse
|
134
|
Gollisch T, Meister M. Eye smarter than scientists believed: neural computations in circuits of the retina. Neuron 2010; 65:150-64. [PMID: 20152123 DOI: 10.1016/j.neuron.2009.12.009] [Citation(s) in RCA: 376] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We rely on our visual system to cope with the vast barrage of incoming light patterns and to extract features from the scene that are relevant to our well-being. The necessary reduction of visual information already begins in the eye. In this review, we summarize recent progress in understanding the computations performed in the vertebrate retina and how they are implemented by the neural circuitry. A new picture emerges from these findings that helps resolve a vexing paradox between the retina's structure and function. Whereas the conventional wisdom treats the eye as a simple prefilter for visual images, it now appears that the retina solves a diverse set of specific tasks and provides the results explicitly to downstream brain areas.
Collapse
Affiliation(s)
- Tim Gollisch
- Max Planck Institute of Neurobiology, Visual Coding Group, Am Klopferspitz 18, 82152 Martinsried, Germany
| | | |
Collapse
|
135
|
Li W, Chen S, DeVries SH. A fast rod photoreceptor signaling pathway in the mammalian retina. Nat Neurosci 2010; 13:414-6. [PMID: 20190742 PMCID: PMC2847031 DOI: 10.1038/nn.2507] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 01/15/2010] [Indexed: 11/23/2022]
Abstract
Rod photoreceptors were recently shown to contact Off cone bipolar cells, providing a novel pathway for rod signal flow in the mammalian retina. By recording from pairs of rods and Off cone bipolar cells in the ground squirrel, we measured the synaptic responses of mammalian rods unfiltered by the slow kinetics of the rod bipolar cell response. We show that vesicle fusion and turnover in mammalian rods is fast, and that this new pathway can mediate rapid signaling.
Collapse
Affiliation(s)
- Wei Li
- Unit on Retinal Neurophysiology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA.
| | | | | |
Collapse
|
136
|
Pang JJ, Gao F, Lem J, Bramblett DE, Paul DL, Wu SM. Direct rod input to cone BCs and direct cone input to rod BCs challenge the traditional view of mammalian BC circuitry. Proc Natl Acad Sci U S A 2010; 107:395-400. [PMID: 20018684 PMCID: PMC2806755 DOI: 10.1073/pnas.0907178107] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bipolar cells are the central neurons of the retina that transmit visual signals from rod and cone photoreceptors to third-order neurons in the inner retina and the brain. A dogma set forth by early anatomical studies is that bipolar cells in mammalian retinas receive segregated rod/cone synaptic inputs (either from rods or from cones), and here, we present evidence that challenges this traditional view. By analyzing light-evoked cation currents from morphologically identified depolarizing bipolar cells (DBCs) in the wild-type and three pathway-specific knockout mice (rod transducin knockout [Tralpha(-/-)], connexin36 knockout [Cx36(-/-)], and transcription factor beta4 knockout [Bhlhb4(-/-)]), we show that a subpopulation of rod DBCs (DBC(R2)s) receives substantial input directly from cones and a subpopulation of cone DBCs (DBC(C1)s) receives substantial input directly from rods. These results provide evidence of the existence of functional rod-DBC(C) and cone-DBC(R) synaptic pathways in the mouse retina as well as the previously proposed rod hyperpolarizing bipolar-cells pathway. This is grounds for revising the mammalian rod/cone bipolar cell dogma.
Collapse
Affiliation(s)
- Ji-Jie Pang
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030
| | - Fan Gao
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030
| | - Janis Lem
- Department of Ophthalmology, Programs in Genetics, Neuroscience, Cell and Molecular and Developmental Biology, Tufts University School of Medicine, Boston, MA 02111
| | - Debra E. Bramblett
- Department of Medical Education, Texas Tech University Health Sciences Center, El Paso, TX 79905; and
| | - David L. Paul
- Department of Neurobiology, Harvard Medical School, Boston, MA 02135
| | - Samuel M. Wu
- Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030
| |
Collapse
|
137
|
Dumitrescu ON, Pucci FG, Wong KY, Berson DM. Ectopic retinal ON bipolar cell synapses in the OFF inner plexiform layer: contacts with dopaminergic amacrine cells and melanopsin ganglion cells. J Comp Neurol 2009; 517:226-44. [PMID: 19731338 DOI: 10.1002/cne.22158] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A key principle of retinal organization is that distinct ON and OFF channels are relayed by separate populations of bipolar cells to different sublaminae of the inner plexiform layer (IPL). ON bipolar cell axons have been thought to synapse exclusively in the inner IPL (the ON sublamina) onto dendrites of ON-type amacrine and ganglion cells. However, M1 melanopsin-expressing ganglion cells and dopaminergic amacrine (DA) cells apparently violate this dogma. Both are driven by ON bipolar cells, but their dendrites stratify in the outermost IPL, within the OFF sublamina. Here, in the mouse retina, we show that some ON cone bipolar cells make ribbon synapses in the outermost OFF sublayer, where they costratify with and contact the dendrites of M1 and DA cells. Whole-cell recording and dye filling in retinal slices indicate that type 6 ON cone bipolars provide some of this ectopic ON channel input. Imaging studies in dissociated bipolar cells show that these ectopic ribbon synapses are capable of vesicular release. There is thus an accessory ON sublayer in the outer IPL.
Collapse
Affiliation(s)
- Olivia N Dumitrescu
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | | | | | | |
Collapse
|
138
|
Ishii M, Morigiwa K, Takao M, Nakanishi S, Fukuda Y, Mimura O, Tsukamoto Y. Ectopic synaptic ribbons in dendrites of mouse retinal ON- and OFF-bipolar cells. Cell Tissue Res 2009; 338:355-75. [PMID: 19859741 PMCID: PMC2779389 DOI: 10.1007/s00441-009-0880-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 09/08/2009] [Indexed: 11/12/2022]
Abstract
The ectopic distribution of synaptic ribbons in dendrites of mouse retinal bipolar cells was examined by using genetic ablation of metabotropic glutamate receptor subtype 6 (mGluR6), electron microscopy, and immunocytochemistry. Ectopic ribbons were observed in dendrites of rod and ON-cone bipolar cells in the mGluR6-deficient mouse but not in those of wild-type mice. The number of rod spherules facing the ectopic ribbons in mGluR6-deficient rod bipolar dendrites increased gradually during early growth and reached a plateau level of about 20% at 12 weeks. These ectopic ribbons were immunopositive for RIBEYE, a ribbon-specific protein, but the associated vesicles were immunonegative for synaptophysin, a synaptic-vesicle-specific protein. The presence of ectopic ribbons was correlated with an increase in the roundness of the invaginating dendrites of the rod bipolar cells. We further confirmed ectopic ribbons in dendrites of OFF-cone bipolar cells in wild-type retinas. Of the four types of OFF-cone bipolar cells (T1-T4), only the T2-type, which had a greater number of synaptic ribbons at the axon terminal and a thicker axon cylinder than the other types, had ectopic ribbons. Light-adapted experiments revealed that, in wild-type mice under enhanced-light adaptation (considered similar to the mGluR6-deficient state), the roundness in the invaginating dendrites and axon terminals of rod bipolar cells increased, but no ectopic ribbons were detected. Based on these findings and known mechanisms for neurotransmitter release and protein trafficking, the possible mechanisms underlying the ectopic ribbons are discussed on the basis of intracellular transport for the replenishment of synaptic proteins.
Collapse
Affiliation(s)
- Masaaki Ishii
- Department of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501 Japan
- Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501 Japan
| | | | - Motoharu Takao
- Department of Human and Information Science, Tokai University, Hiratsuka, Kanagawa 259-1292 Japan
| | | | - Yutaka Fukuda
- Department of Physiology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 Japan
| | - Osamu Mimura
- Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501 Japan
| | - Yoshihiko Tsukamoto
- Department of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501 Japan
| |
Collapse
|
139
|
Logiudice L, Sterling P, Matthews G. Vesicle recycling at ribbon synapses in the finely branched axon terminals of mouse retinal bipolar neurons. Neuroscience 2009; 164:1546-56. [PMID: 19778591 DOI: 10.1016/j.neuroscience.2009.09.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 09/09/2009] [Accepted: 09/11/2009] [Indexed: 11/30/2022]
Abstract
In retinal bipolar neurons, synaptic ribbons mark the presence of exocytotic active zones in the synaptic terminal. It is unknown, however, where compensatory vesicle retrieval is localized in this cell type and by what mechanism(s) excess membrane is recaptured. To determine whether endocytosis is localized or diffuse in mouse bipolar neurons, we imaged FM4-64 to track vesicles in cells whose synaptic ribbons were tagged with a fluorescent peptide. In synaptic terminals, vesicle retrieval occurred at discrete sites that were spatially consistent over multiple stimuli, indicative of endocytotic "hot spots." Retrieval sites were spatially correlated with fluorescently labeled synaptic ribbons. Electron microscopy (EM) analysis of bipolar cell terminals after photoconversion of internalized FM dye revealed that almost all of the dye was contained within vesicles approximately 30 nm in diameter. Clathrin-coated vesicles were observed budding from the plasma membrane and within the cytosol, and application of dynasore, a dynamin inhibitor, arrested membrane retrieval just after the budding stage. We conclude that synaptic vesicles in the fine branches of mouse bipolar axon terminals are retrieved locally near active zones, at least in part via a clathrin-mediated pathway.
Collapse
Affiliation(s)
- L Logiudice
- Department of Neurobiology and Behavior, State University of New York, Stony Brook, NY 11794-5230, USA
| | | | | |
Collapse
|
140
|
Abd-El-Barr MM, Pennesi ME, Saszik SM, Barrow AJ, Lem J, Bramblett DE, Paul DL, Frishman LJ, Wu SM. Genetic dissection of rod and cone pathways in the dark-adapted mouse retina. J Neurophysiol 2009; 102:1945-55. [PMID: 19587322 PMCID: PMC2746771 DOI: 10.1152/jn.00142.2009] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 07/02/2009] [Indexed: 01/25/2023] Open
Abstract
A monumental task of the mammalian retina is to encode an enormous range (>10(9)-fold) of light intensities experienced by the animal in natural environments. Retinal neurons carry out this task by dividing labor into many parallel rod and cone synaptic pathways. Here we study the operational plan of various rod- and cone-mediated pathways by analyzing electroretinograms (ERGs), primarily b-wave responses, in dark-adapted wildtype, connexin36 knockout, depolarizing rod-bipolar cell (DBCR) knockout, and rod transducin alpha-subunit knockout mice [WT, Cx36(-/-), Bhlhb4(-/-), and Tralpha(-/-)]. To provide additional insight into the cellular origins of various components of the ERG, we compared dark-adapted ERG responses with response dynamic ranges of individual retinal cells recorded with patch electrodes from dark-adapted mouse retinas published from other studies. Our results suggest that the connexin36-mediated rod-cone coupling is weak when light stimulation is weak and becomes stronger as light stimulation increases in strength and that rod signals may be transmitted to some DBCCs via direct chemical synapses. Moreover, our analysis indicates that DBCR responses contribute about 80% of the overall DBC response to scotopic light and that rod and cone signals contribute almost equally to the overall DBC responses when stimuli are strong enough to saturate the rod bipolar cell response. Furthermore, our study demonstrates that analysis of ERG b-wave of dark-adapted, pathway-specific mutants can be used as an in vivo tool for dissecting rod and cone synaptic pathways and for studying the functions of pathway-specific gene products in the retina.
Collapse
Affiliation(s)
- Muhammad M Abd-El-Barr
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, One Baylor Plaza, NC-205, Houston, TX 77030, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
141
|
Bloomfield SA, Völgyi B. The diverse functional roles and regulation of neuronal gap junctions in the retina. Nat Rev Neurosci 2009; 10:495-506. [PMID: 19491906 PMCID: PMC3381350 DOI: 10.1038/nrn2636] [Citation(s) in RCA: 270] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Electrical synaptic transmission through gap junctions underlies direct and rapid neuronal communication in the CNS. The diversity of functional roles that electrical synapses have is perhaps best exemplified in the vertebrate retina, in which gap junctions are formed by each of the five major neuron types. These junctions are dynamically regulated by ambient illumination and by circadian rhythms acting through light-activated neuromodulators such as dopamine and nitric oxide, which in turn activate intracellular signalling pathways in the retina.The networks formed by electrically coupled neurons are plastic and reconfigurable, and those in the retina are positioned to play key and diverse parts in the transmission and processing of visual information at every retinal level.
Collapse
Affiliation(s)
- Stewart A Bloomfield
- Department of Physiology & Neuroscience, New York University School of Medicine, 550 First Avenue, New York, New York 10016, USA.
| | | |
Collapse
|
142
|
Bai X, Zhu J, Yang J, Savoie BT, Wang GY. Mechanisms that limit the light stimulus frequency following through the DL-2-amino-4-phosphonobutyric acid sensitive and insensitive rod Off-pathways. Neuroscience 2009; 162:184-94. [PMID: 19406212 DOI: 10.1016/j.neuroscience.2009.04.060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 04/24/2009] [Accepted: 04/24/2009] [Indexed: 11/18/2022]
Abstract
In the retina, rod signal pathways process scotopic visual information. Light decrements are mediated by two distinct groups of rod pathways in the dark-adapted retina that can be differentiated on the basis of their sensitivity to the glutamate agonist dl-2-amino-4-phosphonobutyric acid (APB). We have found that the APB sensitive and insensitive rod Off-pathways signal different light decrement information: the APB sensitive rod Off-pathway conveys slow and low frequency light signals, whereas the APB insensitive rod Off-pathways mediate fast and high frequency light signals [Wang GY (2006) Unique functional properties of the APB sensitive and insensitive rod pathways signaling light decrements in mouse retinal ganglion cells. Vis Neurosci 23:127-135]. However, the mechanisms which limit the frequency following through the APB sensitive and insensitive rod Off-pathways remain unknown. In the current study, whole-cell patch-clamp recordings were made from ganglion cells in dark and light adapted mouse retina to identify the mechanisms that limit the frequency following through the APB sensitive and insensitive rod Off-pathways. The results showed that the sites from AII amacrine cells to Off cone bipolar cells are the major mechanisms that limit the frequency following through the APB sensitive rod Off-pathway. In the APB insensitive rod Off-pathways, rods themselves limited the frequency following through these pathways. Moreover, ganglion cells were able to follow higher frequencies under photopic conditions than under scotopic conditions. The Off responses followed lower frequencies than On responses under photopic conditions. This finding was observed in cells that yielded On or Off responses only as well as in On-Off cells.
Collapse
Affiliation(s)
- X Bai
- Department of Structural and Cellular Biology, School of Medicine, Tulane University, 1430 Tulane Avenue, SL-49, New Orleans, LA 70112, USA
| | | | | | | | | |
Collapse
|
143
|
Kihara AH, Paschon V, Cardoso CM, Higa GSV, Castro LM, Hamassaki DE, Britto LRG. Connexin36, an essential element in the rod pathway, is highly expressed in the essentially rodless retina of Gallus gallus. J Comp Neurol 2009; 512:651-63. [PMID: 19051319 DOI: 10.1002/cne.21920] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Electrical coupling provided by connexins (Cx) in gap junctions (GJ) plays important roles in both the developing and the mature retina. In mammalian nocturnal species, Cx36 is an essential component in the rod pathway, the retinal circuit specialized for night, scotopic vision. Here, we report the expression of Cx36 in a species (Gallus gallus) that phylogenetic development endows with an essentially rodless retina. Cx36 gene is very highly expressed in comparison with other Cxs previously described in the adult retina, such as Cx43, Cx45, and Cx50. Moreover, real-time PCR, Western blot, and immunofluorescence all revealed that Cx36 expression massively increased over time during development. We thoroughly examined Cx36 in the inner and outer plexiform layers, where this protein was particularly abundant. Cx36 was observed mainly in the off sublamina of the inner plexiform layer rather than in the on sublamina previously described in the mammalian retina. In addition, Cx36 colocalized with specific cell markers, revealing the expression of this protein in distinct amacrine cells. To investigate further the involvement of Cx36 in visual processing, we examined its functional regulation in retinas from dark-adapted animals. Light deprivation markedly up-regulates Cx36 gene expression in the retina, resulting in an increased accumulation of the protein within and between cone synaptic terminals. In summary, the developmental regulation of Cx36 expression results in particular circuitry-related roles in the chick retina. Moreover, this study demonstrated that Cx36 onto- and phylogenesis in the vertebrate retina simultaneously exhibit similarities and particularities.
Collapse
Affiliation(s)
- A H Kihara
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
| | | | | | | | | | | | | |
Collapse
|
144
|
Cameron MA, Barnard AR, Hut RA, Bonnefont X, van der Horst GTJ, Hankins MW, Lucas RJ. Electroretinography of wild-type and Cry mutant mice reveals circadian tuning of photopic and mesopic retinal responses. J Biol Rhythms 2009; 23:489-501. [PMID: 19060258 DOI: 10.1177/0748730408325874] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Attempts to understand circadian organization in the mammalian retina have concentrated increasingly on the mouse. However, rather little is known regarding circadian control of retinal light responses in this species. Here, the authors address this deficit using electroretinogram (ERG) recordings in C57BL/6 mice to evaluate rhythmicity in the wild-type retina and to identify the consequences of circadian clock loss in Cry1(- /-)Cry2(-/-) mice. They observe a circadian rhythm in the ERG waveform under light-adapted, cone-isolating conditions in wild-type mice, with b-wave speed and amplitude and the total power of oscillatory potentials all enhanced during the day. Wild types also exhibited a circadian dependence to ERG amplitude under dark-adapted conditions, but only when the flash stimulus was sufficiently bright to lie within the response range of cones. Cry1(-/ -)Cry2(-/-) mice lacked rhythmicity but retained superficially normal ERGs under all conditions suggesting that circadian clocks are dispensable for general retinal function. However, clock loss was associated with subtle abnormalities in retinal responses, with the amplitude of cone and mixed rod + cone ERGs constitutively enhanced. These data suggest that circadian clocks drive a fundamental fine-tuning of retinal pathways that is particularly apparent under conditions in which vision relies upon either cones alone or mixed rod + cone photoreception.
Collapse
Affiliation(s)
- Morven A Cameron
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Manchester, UK
| | | | | | | | | | | | | |
Collapse
|
145
|
Abstract
To better understand synaptic signaling at the mammalian rod bipolar cell terminal and pave the way for applying genetic approaches to the study of visual information processing in the mammalian retina, synaptic vesicle dynamics and intraterminal calcium were monitored in terminals of acutely isolated mouse rod bipolar cells and the number of ribbon-style active zones quantified. We identified a releasable pool, corresponding to a maximum of 7 s. The presence of a smaller, rapidly releasing pool and a small, fast component of refilling was also suggested. Following calcium channel closure, membrane surface area was restored to baseline with a time constant that ranged from 2 to 21 s depending on the magnitude of the preceding Ca2+ transient. In addition, a brief, calcium-dependent delay often preceded the start of onset of membrane recovery. Thus, several aspects of synaptic vesicle dynamics appear to be conserved between rod-dominant bipolar cells of fish and mammalian rod bipolar cells. A major difference is that the number of vesicles available for release is significantly smaller in the mouse rod bipolar cell, both as a function of the total number per neuron and on a per active zone basis.
Collapse
|
146
|
Wu SM. From retinal circuitry to eye diseases--in memory of Henk Spekreijse. Vision Res 2008; 49:992-5. [PMID: 18948133 DOI: 10.1016/j.visres.2008.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 08/27/2008] [Accepted: 10/02/2008] [Indexed: 10/21/2022]
Abstract
This article summarizes our recent works on stratum-by-stratum structure-function rules for synaptic contacts between retinal bipolar cells and third-order retinal neurons in the inner plexiform layer. These rules were derived from large-scale voltage clamp recordings of various types of bipolar cells in the tiger salamander retina, and they appear applicable to bipolar cells in the mouse and other mammalian species. This review also gives a brief account of how we used pathway-specific knockout mouse models to dissect rod and cone signaling channels in the mammalian retina. Furthermore, studies on cellular and genetic mechanisms underlying several neurodegenerative retinal disorders are described.
Collapse
Affiliation(s)
- Samuel M Wu
- Cullen Eye Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
| |
Collapse
|
147
|
Xu HP, Tian N. Glycine receptor-mediated synaptic transmission regulates the maturation of ganglion cell synaptic connectivity. J Comp Neurol 2008; 509:53-71. [PMID: 18425804 DOI: 10.1002/cne.21727] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It is well documented that neuronal activity is required for the developmental segregation of retinal ganglion cell (RGC) synaptic connectivity with ON and OFF bipolar cells in mammalian retina. Our recent study showed that light deprivation preferentially blocked the developmental RGC dendritic redistribution from the center to sublamina a of the inner plexiform layer (IPL). To determine whether OFF signals in visual stimulation are required for OFF RGC dendritic development, the light-evoked responses and dendritic stratification patterns of RGCs in Spastic mutant mice, in which the OFF signal transmission in the rod pathway is largely blocked due to a reduction of glycine receptor (GlyR) expression, were quantitatively studied at different ages and rearing conditions. The dendritic distribution in the IPL of these mice was indistinguishable from wildtype controls at the age of postnatal day (P)12. However, the adult Spastic mutants had altered RGC light-evoked synaptic inputs from ON and OFF pathways, which could not be mimicked by pharmacologically blocking of glycinergic synaptic transmission on age-matched wildtype animals. Spastic mutation also blocked the developmental redistribution of RGC dendrites from the center to sublamina a of the IPL, which mimicked the effects induced by light deprivation on wildtype animals. Moreover, light deprivation of the Spastic mutants had no additional impact on the RGC dendritic distribution and light response patterns. We interpret these results as that visual stimulation regulates the maturation of RGC synaptic activity and connectivity primarily through GlyR-mediated synaptic transmission.
Collapse
Affiliation(s)
- Hong-Ping Xu
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | | |
Collapse
|
148
|
Beaudoin DL, Manookin MB, Demb JB. Distinct expressions of contrast gain control in parallel synaptic pathways converging on a retinal ganglion cell. J Physiol 2008; 586:5487-502. [PMID: 18832424 DOI: 10.1113/jphysiol.2008.156224] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Visual neurons adapt to increases in stimulus contrast by reducing their response sensitivity and decreasing their integration time, a collective process known as 'contrast gain control.' In retinal ganglion cells, gain control arises at two stages: an intrinsic mechanism related to spike generation, and a synaptic mechanism in retinal pathways. Here, we tested whether gain control is expressed similarly by three synaptic pathways that converge on an OFF alpha/Y-type ganglion cell: excitatory inputs driven by OFF cone bipolar cells; inhibitory inputs driven by ON cone bipolar cells; and inhibitory inputs driven by rod bipolar cells. We made whole-cell recordings of membrane current in guinea pig ganglion cells in vitro. At high contrast, OFF bipolar cell-mediated excitatory input reduced gain and shortened integration time. Inhibitory input was measured by clamping voltage near 0 mV or by recording in the presence of ionotropic glutamate receptor (iGluR) antagonists to isolate the following circuit: cone --> ON cone bipolar cell --> AII amacrine cell --> OFF ganglion cell. At high contrast, this input reduced gain with no effect on integration time. Mean luminance was reduced 1000-fold to recruit the rod bipolar pathway: rod --> rod bipolar cell --> AII cell --> OFF ganglion cell. The spiking response, measured with loose-patch recording, adapted despite essentially no gain control in synaptic currents. Thus, cone bipolar-driven pathways adapt differently, with kinetic effects confined to the excitatory OFF pathway. The ON bipolar-mediated inhibition reduced gain at high contrast by a mechanism that did not require an iGluR. Under rod bipolar-driven conditions, ganglion cell firing showed gain control that was explained primarily by an intrinsic property.
Collapse
|
149
|
Joselevitch C, Kamermans M. Retinal parallel pathways: seeing with our inner fish. Vision Res 2008; 49:943-59. [PMID: 18722397 DOI: 10.1016/j.visres.2008.07.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 06/21/2008] [Accepted: 07/18/2008] [Indexed: 10/21/2022]
Abstract
The general organization of the vertebrate retina is highly conserved, in spite of structural variations that occur in different animal classes. The retinas of cyprinid fish, for example, differ in many aspects from those of primates. However, these differences are in the same order of magnitude as those found among mammalian species. Therefore, it is important to consider whether these changes are minor variations on the same theme or whether they lead to fundamentally different functions. In this light, we compare the retinal organization of teleost fish and mammals as regards parallel processing and discuss their many similarities.
Collapse
Affiliation(s)
- Christina Joselevitch
- Retinal Signal Processing, The Netherlands Institute for Neuroscience, The Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, Amsterdam, The Netherlands
| | | |
Collapse
|
150
|
Petrides A, Trexler EB. Differential output of the high-sensitivity rod photoreceptor: AII amacrine pathway. J Comp Neurol 2008; 507:1653-62. [PMID: 18241050 DOI: 10.1002/cne.21617] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In the mammalian retina, the scotopic threshold of ganglion cells is in part dependent on how rod inputs are summed by their presynaptic cone bipolar cells. For ON cone bipolar cells, there are two anatomical routes for rod signals: 1) cone photoreceptors receive inputs via gap junctions with the surrounding, more numerous rods; and 2) ON cone bipolar cells receive highly convergent input via gap junctions with AII amacrine cells, which each receive input from hundreds of rods. Rod-cone coupling is thought to be utilized at higher photon fluxes relative to the AII-ON cone bipolar pathway due to the impedance mismatch of a single small rod driving a larger cone. Furthermore, it is widely held that the convergence of high-gain chemical synapses onto AIIs confers the highest sensitivity to ON cone bipolar cells and ganglion cells. A lack of coupling between one or more types of ON cone bipolar cells and AIIs would obviate this high-sensitivity pathway and explain the existence of ganglion cells with elevated scotopic thresholds. To investigate this possibility, we examined Neurobiotin and glycine diffusion from AIIs to bipolar cells and found that approximately one-fifth of ON cone bipolar cells are not coupled to AIIs. Unlike AII-AII coupling, which changes with ambient background intensity, the fraction of noncoupled ON cone bipolar cells was unaltered by dark or light adaptation. These data suggest that one of five morphologically distinct ON cone bipolar cell types is not coupled to AIIs and suggest that AII-ON cone bipolar coupling is modulated differently from AII-AII coupling.
Collapse
Affiliation(s)
- Artemis Petrides
- Department of Ophthalmology, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | |
Collapse
|