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Pang JJ. The Variety of Mechanosensitive Ion Channels in Retinal Neurons. Int J Mol Sci 2024; 25:4877. [PMID: 38732096 PMCID: PMC11084373 DOI: 10.3390/ijms25094877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/16/2024] [Accepted: 04/20/2024] [Indexed: 05/13/2024] Open
Abstract
Alterations in intraocular and external pressure critically involve the pathogenesis of glaucoma, traumatic retinal injury (TRI), and other retinal disorders, and retinal neurons have been reported to express multiple mechanical-sensitive channels (MSCs) in recent decades. However, the role of MSCs in visual functions and pressure-related retinal conditions has been unclear. This review will focus on the variety and functional significance of the MSCs permeable to K+, Na+, and Ca2+, primarily including the big potassium channel (BK); the two-pore domain potassium channels TRAAK and TREK; Piezo; the epithelial sodium channel (ENaC); and the transient receptor potential channels vanilloid TRPV1, TRPV2, and TRPV4 in retinal photoreceptors, bipolar cells, horizontal cells, amacrine cells, and ganglion cells. Most MSCs do not directly mediate visual signals in vertebrate retinas. On the other hand, some studies have shown that MSCs can open in physiological conditions and regulate the activities of retinal neurons. While these data reasonably predict the crossing of visual and mechanical signals, how retinal light pathways deal with endogenous and exogenous mechanical stimulation is uncertain.
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Affiliation(s)
- Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA
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2
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Country MW, Haase K, Blank K, Canez CR, Roberts JA, Campbell BFN, Smith JC, Pelling AE, Jonz MG. Seasonal changes in membrane structure and excitability in retinal neurons of goldfish (Carassius auratus) under constant environmental conditions. J Exp Biol 2022; 225:275230. [PMID: 35485205 DOI: 10.1242/jeb.244238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 04/25/2022] [Indexed: 11/20/2022]
Abstract
Seasonal modifications in the structure of cellular membranes occur as an adaptive measure to withstand exposure to prolonged environmental change. Little is known about whether such changes may occur independently of external cues, such as photoperiod or temperature, or how they may impact the central nervous system. We compared membrane properties of neurons isolated from the retina of goldfish (Carassius auratus), an organism well-adapted to extreme environmental change, during the summer and winter months. Goldfish were maintained in a facility under constant environmental conditions throughout the year. Analysis of whole-retina phospholipid composition using mass spectrometry-based lipidomics revealed a two-fold increase in phosphatidylethanolamine species during the winter, suggesting an increase in cell membrane fluidity. Atomic force microscopy was used to produce localized, nanoscale-force deformation of neuronal membranes. Measurement of Young's modulus indicated increased membrane-cortical stiffness (or decreased elasticity) in neurons isolated during the winter. Voltage-clamp electrophysiology was used to assess physiological changes in neurons between seasons. Winter neurons displayed a hyperpolarized reversal potential (Vrev) and a significantly lower input resistance (Rin) compared to summer neurons. This was indicative of a decrease in membrane excitability during the winter. Subsequent measurement of intracellular Ca2+ activity using Fura-2 microspectrofluorometry confirmed a reduction in action potential activity, including duration and action potential profile, in neurons isolated during the winter. These studies demonstrate chemical and biophysical changes that occur in retinal neurons of goldfish throughout the year without exposure to seasonal cues, and suggest a novel mechanism of seasonal regulation of retinal activity.
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Affiliation(s)
| | | | - Katrin Blank
- Department of Chemistry, Carleton University, Canada
| | | | | | | | | | | | - Michael G Jonz
- Department of Biology, University of Ottawa, Canada.,Brain and Mind Research Institute, University of Ottawa, Canada
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3
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Schilardi G, Kleinlogel S. Two Functional Classes of Rod Bipolar Cells in the Healthy and Degenerated Optogenetically Treated Murine Retina. Front Cell Neurosci 2022; 15:809531. [PMID: 35095426 PMCID: PMC8793500 DOI: 10.3389/fncel.2021.809531] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/20/2021] [Indexed: 11/25/2022] Open
Abstract
Bipolar cells have become successful targets for optogenetic gene therapies that restore vision after photoreceptor degeneration. However, degeneration was shown to cause changes in neuronal connectivity and protein expression, which may impact the quality of synthetically restored signaling. Further, the expression of an optogenetic protein may alter passive membrane properties of bipolar cells affecting signal propagation. We here investigated the passive membrane properties of rod bipolar cells in three different systems, the healthy retina, the degenerated retina, and the degenerated retina expressing the optogenetic actuator Opto-mGluR6. We found that, based on the shape of their current-voltage relations, rod bipolar cells in healthy and degenerated retinas form two clear functional groups (type 1 and type 2 cells). Depolarizing the membrane potential changed recorded current-voltage curves from type 1 to type 2, confirming a single cell identity with two functional states. Expression of Opto-mGluR6 did not alter the passive properties of the rod bipolar cell. With progressing degeneration, dominant outward rectifying currents recorded in type 2 rod bipolar cells decreased significantly. We demonstrate that this is caused by a downregulation of BK channel expression in the degenerated retina. Since this BK conductance will normally recover the membrane potential after RBCs are excited by open TRPM1 channels, a loss in BK will decrease high-pass filtering at the rod bipolar cell level. A better understanding of the changes of bipolar cell physiology during retinal degeneration may pave the way to optimize future treatment strategies of blindness.
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4
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Wen JY, Zhang J, Chen S, Chen Y, Zhang Y, Ma ZY, Zhang F, Xie WM, Fan YF, Duan JS, Chen ZW. Endothelium-derived hydrogen sulfide acts as a hyperpolarizing factor and exerts neuroprotective effects via activation of large-conductance Ca 2+ -activated K + channels. Br J Pharmacol 2021; 178:4155-4175. [PMID: 34216027 DOI: 10.1111/bph.15607] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/15/2021] [Accepted: 06/18/2021] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND AND PURPOSE Endothelium-derived hyperpolarizing factor (EDHF) has been suggested as a therapeutic target for vascular protection against ischaemic brain injury. However, the molecular entity of EDHF and its action on neurons remains unclear. This study was undertaken to demonstrate whether the hydrogen sulfide (H2 S) acts as EDHF and exerts neuroprotective effect via large-conductance Ca2+ -activated K+ (BKCa /KCa 1.1) channels. EXPERIMENTAL APPROACH The whole-cell patch-clamp technology was used to record the changes of BKCa currents in rat neurons induced by EDHF. The cerebral ischaemia/reperfusion model of mice and oxygen-glucose deprivation/reoxygenation (OGD/R) model of neurons were used to explore the neuroprotection of EDHF by activating BKCa channels in these neurons. KEY RESULTS Increases of BKCa currents and membrane hyperpolarization in hippocampal neurons induced by EDHF could be markedly inhibited by BKCa channel inhibitor iberiotoxin or endothelial H2 S synthase inhibitor propargylglycine. The H2 S donor, NaHS-induced BKCa current and membrane hyperpolarization in neurons were also inhibited by iberiotoxin, suggesting that H2 S acts as EDHF and activates the neuronal BKCa channels. Besides, we found that the protective effect of endothelium-derived H2 S against mice cerebral ischaemia/reperfusion injury was disrupted by iberiotoxin. Importantly, the inhibitory effect of NaHS or BKCa channel opener on OGD/R-induced neuron injury and the increment of intracellular Ca2+ level could be inhibited by iberiotoxin but enhanced by co-application with L-type but not T-type calcium channel inhibitor. CONCLUSION AND IMPLICATIONS Endothelium-derived H2 S acts as EDHF and exerts neuroprotective effects via activating the BKCa channels and then inhibiting the T-type calcium channels in hippocampal neurons.
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Affiliation(s)
- Ji-Yue Wen
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Jie Zhang
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Shuo Chen
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Ye Chen
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Yang Zhang
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Zi-Yao Ma
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Fang Zhang
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Wei-Ming Xie
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Yi-Fei Fan
- Department of Physiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Jing-Si Duan
- Department of Cardiovascular Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Zhi-Wu Chen
- Department of Pharmacology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
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5
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Barnes S, Grove JCR, McHugh CF, Hirano AA, Brecha NC. Horizontal Cell Feedback to Cone Photoreceptors in Mammalian Retina: Novel Insights From the GABA-pH Hybrid Model. Front Cell Neurosci 2020; 14:595064. [PMID: 33328894 PMCID: PMC7672006 DOI: 10.3389/fncel.2020.595064] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 09/24/2020] [Indexed: 01/20/2023] Open
Abstract
How neurons in the eye feed signals back to photoreceptors to optimize sensitivity to patterns of light appears to be mediated by one or more unconventional mechanisms. Via these mechanisms, horizontal cells control photoreceptor synaptic gain and enhance key aspects of temporal and spatial center-surround receptive field antagonism. After the transduction of light energy into an electrical signal in photoreceptors, the next key task in visual processing is the transmission of an optimized signal to the follower neurons in the retina. For this to happen, the release of the excitatory neurotransmitter glutamate from photoreceptors is carefully regulated via horizontal cell feedback, which acts as a thermostat to keep the synaptic transmission in an optimal range during changes to light patterns and intensities. Novel findings of a recently described model that casts a classical neurotransmitter system together with ion transport mechanisms to adjust the alkaline milieu outside the synapse are reviewed. This novel inter-neuronal messaging system carries feedback signals using two separate, but interwoven regulated systems. The complex interplay between these two signaling modalities, creating synaptic modulation-at-a-distance, has obscured it’s being defined. The foundations of our understanding of the feedback mechanism from horizontal cells to photoreceptors have been long established: Horizontal cells have broad receptive fields, suitable for providing surround inhibition, their membrane potential, a function of stimulus intensity and size, regulates inhibition of photoreceptor voltage-gated Ca2+ channels, and strong artificial pH buffering eliminates this action. This review compares and contrasts models of how these foundations are linked, focusing on a recent report in mammals that shows tonic horizontal cell release of GABA activating Cl− and HCO3− permeable GABA autoreceptors. The membrane potential of horizontal cells provides the driving force for GABAR-mediated HCO3− efflux, alkalinizing the cleft when horizontal cells are hyperpolarized by light or adding to their depolarization in darkness and contributing to cleft acidification via NHE-mediated H+ efflux. This model challenges interpretations of earlier studies that were considered to rule out a role for GABA in feedback to cones.
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Affiliation(s)
- Steven Barnes
- Doheny Eye Institute, Los Angeles, CA, United States.,Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - James C R Grove
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA, United States
| | | | - Arlene A Hirano
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, United States
| | - Nicholas C Brecha
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, United States.,Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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6
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Yousuf MS, Samtleben S, Lamothe SM, Friedman TN, Catuneanu A, Thorburn K, Desai M, Tenorio G, Schenk GJ, Ballanyi K, Kurata HT, Simmen T, Kerr BJ. Endoplasmic reticulum stress in the dorsal root ganglia regulates large-conductance potassium channels and contributes to pain in a model of multiple sclerosis. FASEB J 2020; 34:12577-12598. [PMID: 32677089 DOI: 10.1096/fj.202001163r] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/25/2020] [Accepted: 07/09/2020] [Indexed: 01/22/2023]
Abstract
Neuropathic pain is a common symptom of multiple sclerosis (MS) and current treatment options are ineffective. In this study, we investigated whether endoplasmic reticulum (ER) stress in dorsal root ganglia (DRG) contributes to pain hypersensitivity in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. Inflammatory cells and increased levels of ER stress markers are evident in post-mortem DRGs from MS patients. Similarly, we observed ER stress in the DRG of mice with EAE and relieving ER stress with a chemical chaperone, 4-phenylbutyric acid (4-PBA), reduced pain hypersensitivity. In vitro, 4-PBA and the selective PERK inhibitor, AMG44, normalize cytosolic Ca2+ transients in putative DRG nociceptors. We went on to assess disease-mediated changes in the functional properties of Ca2+ -sensitive BK-type K+ channels in DRG neurons. We found that the conductance-voltage (GV) relationship of BK channels was shifted to a more positive voltage, together with a more depolarized resting membrane potential in EAE cells. Our results suggest that ER stress in sensory neurons of MS patients and mice with EAE is a source of pain and that ER stress modulators can effectively counteract this phenotype.
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Affiliation(s)
- Muhammad Saad Yousuf
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Samira Samtleben
- Department of Cell Biology, University of Alberta, Edmonton, AB, Canada
| | - Shawn M Lamothe
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Timothy N Friedman
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Ana Catuneanu
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Kevin Thorburn
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Mansi Desai
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Gustavo Tenorio
- Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB, Canada
| | - Geert J Schenk
- Department of Anatomy and Neurosciences, Neuroscience Amsterdam, Amsterdam UMC, VU University Medical Center, VUmc MS Center Amsterdam, Amsterdam, The Netherlands
| | - Klaus Ballanyi
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Harley T Kurata
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Thomas Simmen
- Department of Cell Biology, University of Alberta, Edmonton, AB, Canada
| | - Bradley J Kerr
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Department of Pharmacology, University of Alberta, Edmonton, AB, Canada.,Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB, Canada
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7
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Coskun C, Buyuknacar HS, Cicek F, Gunay I. BK channel openers NS1619 and NS11021 reverse hydrogen peroxide-induced membrane potential changes in skeletal muscle. J Recept Signal Transduct Res 2020; 40:449-455. [PMID: 32326798 DOI: 10.1080/10799893.2020.1756324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Large conductance calcium-activated potassium (BK) channels play a crucial role in the repolarization and after-hyperpolarization phases of the cell membrane. The channel openers are also used in treatment of some diseases, including hypo/hyperkalemic periodic paralysis. However, little is known about the effects of BK channels and the channel activators on membrane potentials in skeletal muscle. In addition, the effects of reactive oxygen species (ROS) on BK channels in skeletal muscle are also unknown. Therefore, the aim of this study was to determine the effects of BK channel openers and ROS on membrane potentials in skeletal muscle fibers. For this purpose, resting membrane potentials and action potentials (AP) of frog gastrocnemius muscles were recorded in the presence of commonly used BK channel openers NS1619 and NS11021, H2O2 (a type of ROS), and both using intracellular microelectrode technique. The channel activators significantly and dose-dependently decreased amplitude and increased rise time of AP but did not impact repolarization. The presence of H2O2 plus NS1619 or NS11021 resulted in significant change because the channel openers completely reversed the deleterious effects of hydrogen peroxide on the repolarization phase of AP in skeletal muscle fibers. In the present study, the contributions of BK channel activation and the modulatory role of H2O2 on membrane potentials was demonstrated in skeletal muscle fibers, for the first time. Moreover, it should be noted that BK channel openers should be used in the treatment of reactive oxygen species-induced skeletal muscle diseases.
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Affiliation(s)
- Cagil Coskun
- Department of Biophysics, Faculty of Medicine, Cukurova University, Adana, Turkey
| | | | - Figen Cicek
- Department of Biophysics, Faculty of Medicine, Cukurova University, Adana, Turkey
| | - Ismail Gunay
- Department of Biophysics, Faculty of Medicine, Cukurova University, Adana, Turkey
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8
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Analysis of tetrodotoxin-sensitive sodium and low voltage-activated calcium channels in developing mouse retinal horizontal cells. Exp Eye Res 2020; 195:108028. [PMID: 32277973 DOI: 10.1016/j.exer.2020.108028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/24/2020] [Accepted: 03/29/2020] [Indexed: 11/21/2022]
Abstract
Expression patterns of voltage-gated ion channels determine the spatio-temporal dynamics of ion currents that supply excitable neurons in developing tissue with proper electrophysiological properties. The purpose of the study was to identify fast cationic inward currents in mouse retinal horizontal cells (HCs) and describe their biophysical properties at different developmental stages. We also aimed to reveal their physiological role in shaping light responses (LRs) in adult HCs. HCs were recorded in horizontal slices of wild-type mouse retina at postnatal stages ranging from p8 through p60. Voltage-dependent inward currents were isolated with appropriate voltage protocols and blockers specific for sodium and T-type calcium channels. LRs were evoked with full-field flashes (130 μW/cm2). Transient and steady inward currents were identified at all developmental stages. Transient currents were mediated by T-type calcium and TTX-sensitive sodium channels, whereas steady currents were blocked by cadmium, indicating the presence of high voltage-activated calcium channels. Activation and steady-state inactivation kinetics of T-type calcium channels revealed a contribution to the resting membrane potential during postnatal development. Additionally, both sodium and T-type calcium channels had an impact on HC LRs at light offset in adult animals. Our results showed that the voltage-dependent inward currents of postnatally developing mouse HCs consist of T-type calcium, TTX-sensitive sodium, and high voltage-activated calcium channels, and that transient ionic currents contributed to light-evoked responses of adult HCs, suggesting a role in HC information processing.
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9
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Country MW, Campbell BFN, Jonz MG. Spontaneous action potentials in retinal horizontal cells of goldfish ( Carassius auratus) are dependent upon L-type Ca 2+ channels and ryanodine receptors. J Neurophysiol 2019; 122:2284-2293. [PMID: 31596629 DOI: 10.1152/jn.00240.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Horizontal cells (HCs) are interneurons of the outer retina that undergo graded changes in membrane potential during the light response and provide feedback to photoreceptors. We characterized spontaneous Ca2+-based action potentials (APs) in isolated goldfish (Carassius auratus) HCs with electrophysiological and intracellular imaging techniques. Transient changes in intracellular Ca2+ concentration ([Ca2+]i) were observed with fura-2 and were abolished by removal of extracellular Ca2+ or by inhibition of Ca2+ channels by 50 µM Cd2+ or 100 µM nifedipine. Inhibition of Ca2+ release from stores with 20 µM ryanodine or 50 µM dantrolene abolished Ca2+ transients and increased baseline [Ca2+]i. This increased baseline was prevented by blocking L-type Ca2+ channels with nifedipine, suggesting that Ca2+-induced Ca2+ release from stores may be needed to inactivate membrane Ca2+ channels. Caffeine (3 mM) increased the frequency of Ca2+ transients, and the store-operated channel antagonist 2-aminoethyldiphenylborinate (100 μM) counteracted this effect. APs were detected with voltage-sensitive dye imaging (FluoVolt) and current-clamp electrophysiology. In current-clamp recordings, regenerative APs were abolished by removal of extracellular Ca2+ or in the presence of 5 mM Co2+ or 100 µM nifedipine, and APs were amplified with 15 mM Ba2+. Collectively, our data suggest that during APs Ca2+ enters through L-type Ca2+ channels and that Ca2+ stores (gated by ryanodine receptors) contribute to the rise in [Ca2+]i. This work may lead to further understanding of the possible role APs have in vision, such as transitioning from light to darkness or modulating feedback from HCs to photoreceptors.NEW & NOTEWORTHY Horizontal cells (HCs) are interneurons of the outer retina that provide inhibitory feedback onto photoreceptors. HCs respond to light via graded changes in membrane potential. We characterized spontaneous action potentials in HCs from goldfish and linked action potential generation to a rise in intracellular Ca2+ via plasma membrane channels and ryanodine receptors. Action potentials may play a role in vision, such as transitioning from light to darkness, or in modulating feedback from HCs to photoreceptors.
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Affiliation(s)
- Michael W Country
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Michael G Jonz
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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10
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Van Hook MJ, Nawy S, Thoreson WB. Voltage- and calcium-gated ion channels of neurons in the vertebrate retina. Prog Retin Eye Res 2019; 72:100760. [PMID: 31078724 PMCID: PMC6739185 DOI: 10.1016/j.preteyeres.2019.05.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/25/2019] [Accepted: 05/01/2019] [Indexed: 02/06/2023]
Abstract
In this review, we summarize studies investigating the types and distribution of voltage- and calcium-gated ion channels in the different classes of retinal neurons: rods, cones, horizontal cells, bipolar cells, amacrine cells, interplexiform cells, and ganglion cells. We discuss differences among cell subtypes within these major cell classes, as well as differences among species, and consider how different ion channels shape the responses of different neurons. For example, even though second-order bipolar and horizontal cells do not typically generate fast sodium-dependent action potentials, many of these cells nevertheless possess fast sodium currents that can enhance their kinetic response capabilities. Ca2+ channel activity can also shape response kinetics as well as regulating synaptic release. The L-type Ca2+ channel subtype, CaV1.4, expressed in photoreceptor cells exhibits specific properties matching the particular needs of these cells such as limited inactivation which allows sustained channel activity and maintained synaptic release in darkness. The particular properties of K+ and Cl- channels in different retinal neurons shape resting membrane potentials, response kinetics and spiking behavior. A remaining challenge is to characterize the specific distributions of ion channels in the more than 100 individual cell types that have been identified in the retina and to describe how these particular ion channels sculpt neuronal responses to assist in the processing of visual information by the retina.
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Affiliation(s)
- Matthew J Van Hook
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Scott Nawy
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA
| | - Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA.
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11
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Grove JCR, Hirano AA, de los Santos J, McHugh CF, Purohit S, Field GD, Brecha NC, Barnes S. Novel hybrid action of GABA mediates inhibitory feedback in the mammalian retina. PLoS Biol 2019; 17:e3000200. [PMID: 30933967 PMCID: PMC6459543 DOI: 10.1371/journal.pbio.3000200] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 04/11/2019] [Accepted: 03/13/2019] [Indexed: 01/06/2023] Open
Abstract
The stream of visual information sent from photoreceptors to second-order bipolar cells is intercepted by laterally interacting horizontal cells that generate feedback to optimize and improve the efficiency of signal transmission. The mechanisms underlying the regulation of graded photoreceptor synaptic output in this nonspiking network have remained elusive. Here, we analyze with patch clamp recording the novel mechanisms by which horizontal cells control pH in the synaptic cleft to modulate photoreceptor neurotransmitter release. First, we show that mammalian horizontal cells respond to their own GABA release and that the results of this autaptic action affect cone voltage-gated Ca2+ channel (CaV channel) gating through changes in pH. As a proof-of-principle, we demonstrate that chemogenetic manipulation of horizontal cells with exogenous anion channel expression mimics GABA-mediated cone CaV channel inhibition. Activation of these GABA receptor anion channels can depolarize horizontal cells and increase cleft acidity via Na+/H+ exchanger (NHE) proton extrusion, which results in inhibition of cone CaV channels. This action is effectively counteracted when horizontal cells are sufficiently hyperpolarized by increased GABA receptor (GABAR)-mediated HCO3- efflux, alkalinizing the cleft and disinhibiting cone CaV channels. This demonstrates how hybrid actions of GABA operate in parallel to effect voltage-dependent pH changes, a novel mechanism for regulating synaptic output.
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Affiliation(s)
- James C. R. Grove
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Neuroscience Graduate Program, University of California, San Francisco, California, United States of America
| | - Arlene A. Hirano
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Janira de los Santos
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Cyrus F. McHugh
- Doheny Eye Institute, University of California, Los Angeles, California, United States of America
| | - Shashvat Purohit
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Greg D. Field
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Nicholas C. Brecha
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Steven Barnes
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Doheny Eye Institute, University of California, Los Angeles, California, United States of America
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada
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12
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Pierce ML, Mehrotra S, Mustoe AC, French JA, Murray TF. A Comparison of the Ability of Leu 8- and Pro 8-Oxytocin to Regulate Intracellular Ca 2+ and Ca 2+-Activated K + Channels at Human and Marmoset Oxytocin Receptors. Mol Pharmacol 2019; 95:376-385. [PMID: 30739093 DOI: 10.1124/mol.118.114744] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/30/2019] [Indexed: 02/02/2023] Open
Abstract
The neurohypophyseal hormone oxytocin (OT) regulates biologic functions in both peripheral tissues and the central nervous system. In the central nervous system, OT influences social processes, including peer relationships, maternal-infant bonding, and affiliative social relationships. In mammals, the nonapeptide OT structure is highly conserved with leucine in the eighth position (Leu8-OT). In marmosets (Callithrix), a nonsynonymous nucleotide substitution in the OXT gene codes for proline in the eighth residue position (Pro8-OT). OT binds to its cognate G protein-coupled receptor (OTR) and exerts diverse effects, including stimulation (Gs) or inhibition (Gi/o) of adenylyl cyclase, stimulation of potassium channel currents (Gi), and activation of phospholipase C (Gq). Chinese hamster ovary cells expressing marmoset or human oxytocin receptors (mOTRs or hOTRs, respectively) were used to characterize OT signaling. At the mOTR, Pro8-OT was more efficacious than Leu8-OT in measures of Gq activation, with both peptides displaying subnanomolar potencies. At the hOTR, neither the potency nor efficacy of Pro8-OT and Leu8-OT differed with respect to Gq signaling. In both mOTR- and hOTR-expressing cells, Leu8-OT was more potent and modestly more efficacious than Pro8-OT in inducing hyperpolarization. In mOTR cells, Leu8-OT-induced hyperpolarization was modestly inhibited by pretreatment with pertussis toxin (PTX), consistent with a minor role for Gi/o activation; however, the Pro8-OT response in mOTR and hOTR cells was PTX insensitive. These findings are consistent with membrane hyperpolarization being largely mediated by a Gq signaling mechanism leading to Ca2+-dependent activation of K+ channels. Evaluation of the influence of apamin, charybdotoxin, paxilline, and TRAM-34 demonstrated involvement of both intermediate and large conductance Ca2+-activated K+ channels.
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Affiliation(s)
- Marsha L Pierce
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska (M.L.P., S.M., T.F.M.); and Department of Psychology, University of Nebraska, Omaha, Nebraska (A.C.M., J.A.F.)
| | - Suneet Mehrotra
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska (M.L.P., S.M., T.F.M.); and Department of Psychology, University of Nebraska, Omaha, Nebraska (A.C.M., J.A.F.)
| | - Aaryn C Mustoe
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska (M.L.P., S.M., T.F.M.); and Department of Psychology, University of Nebraska, Omaha, Nebraska (A.C.M., J.A.F.)
| | - Jeffrey A French
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska (M.L.P., S.M., T.F.M.); and Department of Psychology, University of Nebraska, Omaha, Nebraska (A.C.M., J.A.F.)
| | - Thomas F Murray
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska (M.L.P., S.M., T.F.M.); and Department of Psychology, University of Nebraska, Omaha, Nebraska (A.C.M., J.A.F.)
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Chapot CA, Behrens C, Rogerson LE, Baden T, Pop S, Berens P, Euler T, Schubert T. Local Signals in Mouse Horizontal Cell Dendrites. Curr Biol 2017; 27:3603-3615.e5. [PMID: 29174891 DOI: 10.1016/j.cub.2017.10.050] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/01/2017] [Accepted: 10/19/2017] [Indexed: 01/07/2023]
Abstract
The mouse retina contains a single type of horizontal cell, a GABAergic interneuron that samples from all cone photoreceptors within reach and modulates their glutamatergic output via parallel feedback mechanisms. Because horizontal cells form an electrically coupled network, they have been implicated in global signal processing, such as large-scale contrast enhancement. Recently, it has been proposed that horizontal cells can also act locally at the level of individual cone photoreceptors. To test this possibility physiologically, we used two-photon microscopy to record light stimulus-evoked Ca2+ signals in cone axon terminals and horizontal cell dendrites as well as glutamate release in the outer plexiform layer. By selectively stimulating the two mouse cone opsins with green and UV light, we assessed whether signals from individual cones remain isolated within horizontal cell dendritic tips or whether they spread across the dendritic arbor. Consistent with the mouse's opsin expression gradient, we found that the Ca2+ signals recorded from dendrites of dorsal horizontal cells were dominated by M-opsin and those of ventral horizontal cells by S-opsin activation. The signals measured in neighboring horizontal cell dendritic tips varied markedly in their chromatic preference, arguing against global processing. Rather, our experimental data and results from biophysically realistic modeling support the idea that horizontal cells can process cone input locally, extending the classical view of horizontal cell function. Pharmacologically removing horizontal cells from the circuitry reduced the sensitivity of the cone signal to low frequencies, suggesting that local horizontal cell feedback shapes the temporal properties of cone output.
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Affiliation(s)
- Camille A Chapot
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Graduate Training Centre of Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Christian Behrens
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Graduate Training Centre of Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Bernstein Center for Computational Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Luke E Rogerson
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Graduate Training Centre of Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Bernstein Center for Computational Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Tom Baden
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; School of Life Sciences, University of Sussex, Brighton BN1 9RH, UK
| | - Sinziana Pop
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Graduate Training Centre of Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Philipp Berens
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Bernstein Center for Computational Neuroscience, University of Tübingen, 72076 Tübingen, Germany
| | - Thomas Euler
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany; Bernstein Center for Computational Neuroscience, University of Tübingen, 72076 Tübingen, Germany.
| | - Timm Schubert
- Institute for Ophthalmic Research, University of Tübingen, 72076 Tübingen, Germany; Center for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany.
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14
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Thoreson WB. A surprisingly big role for big K + channels in retinal horizontal cells. J Physiol 2017; 595:4125-4126. [PMID: 28418100 DOI: 10.1113/jp274419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, 68198, USA.,Department of Pharmacology & Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198, USA
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