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Rodríguez-Arzate CA, Noguez-Imm R, Reyes-Ortega P, Rodríguez-Ortiz LR, García-Peña MF, Ordaz RP, Vélez-Uriza F, Cisneros-Mejorado A, Arellano RO, Pérez CI, Hernández-Zimbrón LF, Dégardin J, Simonutti M, Picaud S, Thébault SC. Potential contributions of the intrinsic retinal oscillations recording using non-invasive electroretinogram to bioelectronics. Front Cell Neurosci 2024; 17:1224558. [PMID: 38269118 PMCID: PMC10806452 DOI: 10.3389/fncel.2023.1224558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 12/15/2023] [Indexed: 01/26/2024] Open
Abstract
Targeted electric signal use for disease diagnostics and treatment is emerging as a healthcare game-changer. Besides arrhythmias, treatment-resistant epilepsy and chronic pain, blindness, and perhaps soon vision loss, could be among the pathologies that benefit from bioelectronic medicine. The electroretinogram (ERG) technique has long demonstrated its role in diagnosing eye diseases and early stages of neurodegenerative diseases. Conspicuously, ERG applications are all based on light-induced responses. However, spontaneous, intrinsic activity also originates in retinal cells. It is a hallmark of degenerated retinas and its alterations accompany obesity and diabetes. To the extent that variables extracted from the resting activity of the retina measured by ERG allow the predictive diagnosis of risk factors for type 2 diabetes. Here, we provided a comparison of the baseline characteristics of intrinsic oscillatory activity recorded by ERGs in mice, rats, and humans, as well as in several rat strains, and explore whether zebrafish exhibit comparable activity. Their pattern was altered in neurodegenerative models including the cuprizone-induced demyelination model in mice as well as in the Royal College of Surgeons (RCS-/-) rats. We also discuss how the study of their properties may pave the way for future research directions and treatment approaches for retinopathies, among others.
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Affiliation(s)
- Cynthia Alejandra Rodríguez-Arzate
- Laboratorio de Investigación Traslacional en Salud Visual D-13, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Ramsés Noguez-Imm
- Laboratorio de Investigación Traslacional en Salud Visual D-13, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Pamela Reyes-Ortega
- Laboratorio de Investigación Traslacional en Salud Visual D-13, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Luis Roberto Rodríguez-Ortiz
- Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - María Fernanda García-Peña
- Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Rainald Pablo Ordaz
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Fidel Vélez-Uriza
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Abraham Cisneros-Mejorado
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Rogelio O. Arellano
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Claudia I. Pérez
- Laboratorio de Neurofisiología de los Hábitos, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Luis Fernando Hernández-Zimbrón
- Clínica de Salud Visual, Escuela Nacional de Estudios Superiores, Unidad León, Universidad Nacional Autonóma de México (UNAM), León, Guanajuato, Mexico
| | - Julie Dégardin
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
| | - Manuel Simonutti
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
| | - Serge Picaud
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
| | - Stéphanie C. Thébault
- Laboratorio de Investigación Traslacional en Salud Visual D-13, Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
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Preventable risk factors for type 2 diabetes can be detected using noninvasive spontaneous electroretinogram signals. PLoS One 2023; 18:e0278388. [PMID: 36634073 PMCID: PMC9836271 DOI: 10.1371/journal.pone.0278388] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/15/2022] [Indexed: 01/13/2023] Open
Abstract
Given the ever-increasing prevalence of type 2 diabetes and obesity, the pressure on global healthcare is expected to be colossal, especially in terms of blindness. Electroretinogram (ERG) has long been perceived as a first-use technique for diagnosing eye diseases, and some studies suggested its use for preventable risk factors of type 2 diabetes and thereby diabetic retinopathy (DR). Here, we show that in a non-evoked mode, ERG signals contain spontaneous oscillations that predict disease cases in rodent models of obesity and in people with overweight, obesity, and metabolic syndrome but not yet diabetes, using one single random forest-based model. Classification performance was both internally and externally validated, and correlation analysis showed that the spontaneous oscillations of the non-evoked ERG are altered before oscillatory potentials, which are the current gold-standard for early DR. Principal component and discriminant analysis suggested that the slow frequency (0.4-0.7 Hz) components are the main discriminators for our predictive model. In addition, we established that the optimal conditions to record these informative signals, are 5-minute duration recordings under daylight conditions, using any ERG sensors, including ones working with portative, non-mydriatic devices. Our study provides an early warning system with promising applications for prevention, monitoring and even the development of new therapies against type 2 diabetes.
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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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Trenholm S, Awatramani GB. Origins of spontaneous activity in the degenerating retina. Front Cell Neurosci 2015; 9:277. [PMID: 26283914 PMCID: PMC4518194 DOI: 10.3389/fncel.2015.00277] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 07/06/2015] [Indexed: 01/10/2023] Open
Abstract
Sensory deafferentation resulting from the loss of photoreceptors during retinal degeneration (rd) is often accompanied by a paradoxical increase in spontaneous activity throughout the visual system. Oscillatory discharges are apparent in retinal ganglion cells in several rodent models of rd, indicating that spontaneous activity can originate in the retina. Understanding the biophysical mechanisms underlying spontaneous retinal activity is interesting for two main reasons. First, it could lead to strategies that reduce spontaneous retinal activity, which could improve the performance of vision restoration strategies that aim to stimulate remnant retinal circuits in blind patients. Second, studying emergent network activity could offer general insights into how sensory systems remodel upon deafferentation. Here we provide an overview of the work describing spontaneous activity in the degenerating retina, and outline the current state of knowledge regarding the cellular and biophysical properties underlying spontaneous neural activity.
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Affiliation(s)
- Stuart Trenholm
- Friedrich Miescher Institute for Biomedical Research Basel, Switzerland
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Yee CW, Toychiev AH, Sagdullaev BT. Network deficiency exacerbates impairment in a mouse model of retinal degeneration. Front Syst Neurosci 2012; 6:8. [PMID: 22383900 PMCID: PMC3285818 DOI: 10.3389/fnsys.2012.00008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 02/06/2012] [Indexed: 11/23/2022] Open
Abstract
Neural oscillations play an important role in normal brain activity, but also manifest during Parkinson’s disease, epilepsy, and other pathological conditions. The contribution of these aberrant oscillations to the function of the surviving brain remains unclear. In recording from retina in a mouse model of retinal degeneration (RD), we found that the incidence of oscillatory activity varied across different cell classes, evidence that some retinal networks are more affected by functional changes than others. This aberrant activity was driven by an independent inhibitory amacrine cell oscillator. By stimulating the surviving circuitry at different stages of the neurodegenerative process, we found that this dystrophic oscillator further compromises the function of the retina. These data reveal that retinal remodeling can exacerbate the visual deficit, and that aberrant synaptic activity could be targeted for RD treatment.
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Affiliation(s)
- Christopher W Yee
- Department of Ophthalmology, Burke Medical Research Institute, Weill Medical College of Cornell University White Plains, NY, USA
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Abstract
The loss of photoreceptors during retinal degeneration (RD) is known to lead to an increase in basal activity in remnant neural networks. To identify the source of activity, we combined two-photon imaging with patch-clamp techniques to examine the physiological properties of morphologically identified retinal neurons in a mouse model of RD (rd1). Analysis of activity in rd1 ganglion cells revealed sustained oscillatory (∼10 Hz) synaptic activity in ∼30% of all classes of cells. Oscillatory activity persisted after putative inputs from residual photoreceptor, rod bipolar cell, and inhibitory amacrine cell synapses were pharmacologically blocked, suggesting that presynaptic cone bipolar cells were intrinsically active. Examination of presynaptic rd1 ON and OFF bipolar cells indicated that they rested at relatively negative potentials (less than -50 mV). However, in approximately half the cone bipolar cells, low-amplitude membrane oscillation (∼5 mV, ∼10 Hz) were apparent. Such oscillations were also observed in AII amacrine cells. Oscillations in ON cone bipolar and AII amacrine cells exhibited a weak apparent voltage dependence and were resistant to blockade of synaptic receptors, suggesting that, as in wild-type retina, they form an electrically coupled network. In addition, oscillations were insensitive to blockers of voltage-gated Ca(2+) channels (0.5 mm Cd(2+) and 0.5 mm Ni(2+)), ruling out known mechanisms that underlie oscillatory behavior in bipolar cells. Together, these results indicate that an electrically coupled network of ON cone bipolar/AII amacrine cells constitutes an intrinsic oscillator in the rd1 retina that is likely to drive synaptic activity in downstream circuits.
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Cederlund ML, Morrissey ME, Baden T, Scholz D, Vendrell V, Lagnado L, Connaughton VP, Kennedy BN. Zebrafish Tg(7.2mab21l2:EGFP)ucd2 transgenics reveal a unique population of retinal amacrine cells. Invest Ophthalmol Vis Sci 2011; 52:1613-21. [PMID: 21051702 PMCID: PMC3925879 DOI: 10.1167/iovs.10-5376] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Amacrine cells constitute a diverse, yet poorly characterized, cell population in the inner retina. Here, the authors sought to characterize the morphology, molecular physiology, and electrophysiology of a subpopulation of EGFP-expressing retinal amacrine cells identified in a novel zebrafish transgenic line. METHODS After 7.2 kb of the zebrafish mab21l2 promoter was cloned upstream of EGFP, it was used to create the Tg(7.2mab21l2:EGFP)ucd2 transgenic line. Transgenic EGFP expression was analyzed by fluorescence microscopy in whole mount embryos, followed by detailed analysis of EGFP-expressing amacrine cells using fluorescence microscopy, immunohistochemistry, and electrophysiology. RESULTS A 7.2-kb fragment of the mab21l2 promoter region is sufficient to drive transgene expression in the developing lens and tectum. Intriguingly, EGFP was also observed in differentiated amacrine cells. EGFP-labeled amacrine cells in Tg(7.2mab21l2:EGFP)ucd2 constitute a novel GABA- and glycine-negative amacrine subpopulation. Morphologically, EGFP-expressing cells stratify in sublamina 1 to 2 (type 1 OFF) or sublamina 3 to 4 (type 1 ON) or branch diffusely (type 2). Electrophysiologically, these cells segregate into amacrine cells with somas in the vitreal part of the INL and linear responses to current injection or, alternatively, amacrine cells with somas proximal to the IPL and active oscillatory voltage signals. CONCLUSIONS; The novel transgenic line Tg(7.2mab21l2:EGFP)ucd2 uncovers a unique subpopulation of retinal amacrine cells.
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Affiliation(s)
- Maria L. Cederlund
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Maria E. Morrissey
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Tom Baden
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Dimitri Scholz
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Victor Vendrell
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Leon Lagnado
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | | | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland
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Cellular origin of spontaneous ganglion cell spike activity in animal models of retinitis pigmentosa. J Ophthalmol 2010; 2011. [PMID: 20936060 PMCID: PMC2948917 DOI: 10.1155/2011/507037] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 09/07/2010] [Indexed: 11/25/2022] Open
Abstract
Here we review evidence that loss of photoreceptors due to degenerative retinal disease causes an increase in the rate of spontaneous ganglion spike discharge. Information about persistent spike activity is important since it is expected to add noise to the communication between the eye and the brain and thus impact the design and effective use of retinal prosthetics for restoring visual function in patients blinded by disease. Patch-clamp recordings from identified types of ON and OFF retinal ganglion cells in the adult (36–210 d old) rd1 mouse show that the ongoing oscillatory spike activity in both cell types is driven by strong rhythmic synaptic input from presynaptic neurons that is blocked by CNQX. The recurrent synaptic activity may arise in a negative feedback loop between a bipolar cell and an amacrine cell that exhibits resonant behavior and oscillations in membrane potential when the normal balance between excitation and inhibition is disrupted by the absence of photoreceptor input.
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Park SE, Sun HJ, Lee HJ, Park TK, Ohn YH. The Role of Electroretinography in Assessing the Progression of Diabetic Retinopathy. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2010. [DOI: 10.3341/jkos.2010.51.5.693] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Su Eun Park
- Department of Ophthalmology, Hallym University College of Medicine, Seoul, Korea
| | - Hae Jung Sun
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Bucheon, Korea
| | - Hyun Joon Lee
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Bucheon, Korea
| | - Tae Kwann Park
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Bucheon, Korea
| | - Young-Hoon Ohn
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Bucheon, Korea
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Siapich SA, Banat M, Albanna W, Hescheler J, Lüke M, Schneider T. Antagonists of ionotropic gamma-aminobutyric acid receptors impair the NiCl2-mediated stimulation of the electroretinogram b-wave amplitude from the isolated superfused vertebrate retina. Acta Ophthalmol 2009; 87:854-65. [PMID: 20002018 DOI: 10.1111/j.1755-3768.2008.01387.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE NiCl(2) (15 microM) stimulates the electroretinogram (ERG) b-wave amplitude of vertebrate retina up to 1.5-fold through its blocking of E/R-type voltage-gated Ca(2+) channels. Assuming that such an increase is mediated by blocking the release of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) via ionotropic GABA receptors, we tested the effect of both GABA itself and GABA-receptor antagonists such as (-)bicuculline (1.51-fold increase) and (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA; 1.46-fold increase) on the b-wave amplitude. METHODS Recording of the transretinal potentials from the isolated bovine retina. RESULTS GABA (100 microM) reduced the b-wave amplitude only when NiCl(2) (15 microM) was applied first. Each antagonist applied on its own stimulated the b-wave amplitude only partially: subsequent NiCl(2) superfusion caused a small but additional increase, leading to a 1.69- and a 1.88-fold total increase of the amplitude by Ni(2+) plus (-)bicuculline or Ni(2+) plus TPMPA, respectively. Only the application of both antagonists in combination, before superfusing low NiCl(2) (15 microM), completely prevented subsequent stimulation by NiCl(2) with a similar 1.90-fold total increase of b-wave amplitude. Those retina segments that did not respond to NiCl(2) could not be stimulated by (-)bicuculline and vice versa. CONCLUSION The stimulatory effect of NiCl(2) on the ERG b-wave amplitude is mainly, but not only, mediated by a NiCl(2)-sensitive, Ca(v)2.3-triggered GABA release acting through ionotropic GABA-A and GABA-C receptors.
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Membrane resonance in bursting pacemaker neurons of an oscillatory network is correlated with network frequency. J Neurosci 2009; 29:6427-35. [PMID: 19458214 DOI: 10.1523/jneurosci.0545-09.2009] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Network oscillations typically span a limited range of frequency. In pacemaker-driven networks, including many central pattern generators (CPGs), this frequency range is determined by the properties of bursting pacemaker neurons and their synaptic connections; thus, factors that affect the burst frequency of pacemaker neurons should play a role in determining the network frequency. We examine the role of membrane resonance of pacemaker neurons on the network frequency in the crab pyloric CPG. The pyloric oscillations (frequency of approximately 1 Hz) are generated by a group of pacemaker neurons: the anterior burster (AB) and the pyloric dilator (PD). We examine the impedance profiles of the AB and PD neurons in response to sinusoidal current injections with varying frequency and find that both neuron types exhibit membrane resonance, i.e., demonstrate maximal impedance at a given preferred frequency. The membrane resonance frequencies of the AB and PD neurons fall within the range of the pyloric network oscillation frequency. Experiments with pharmacological blockers and computational modeling show that both calcium currents I(Ca) and the hyperpolarization-activated inward current I(h) are important in producing the membrane resonance in these neurons. We then demonstrate that both the membrane resonance frequency of the PD neuron and its suprathreshold bursting frequency can be shifted in the same direction by either direct current injection or by using the dynamic-clamp technique to inject artificial conductances for I(h) or I(Ca). Together, these results suggest that membrane resonance of pacemaker neurons can be strongly correlated with the CPG oscillation frequency.
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Hirasawa H, Puopolo M, Raviola E. Extrasynaptic release of GABA by retinal dopaminergic neurons. J Neurophysiol 2009; 102:146-58. [PMID: 19403749 DOI: 10.1152/jn.00130.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABA release by dopaminergic amacrine (DA) cells of the mouse retina was detected by measuring Cl- currents generated by isolated perikarya in response to their own neurotransmitter. The possibility that the Cl- currents were caused by GABA release from synaptic endings that had survived the dissociation of the retina was ruled out by examining confocal Z series of the surface of dissociated tyrosine hydroxylase-positive perikarya after staining with antibodies to pre and postsynaptic markers. GABA release was caused by exocytosis because 1) the current events were transient on the millisecond time scale and thus resembled miniature synaptic currents; 2) they were abolished by treatment with a blocker of the vesicular proton pump, bafilomycin A1; and 3) their frequency was controlled by the intracellular Ca2+ concentration. Because DA cell perikarya do not contain presynaptic active zones, release was by necessity extrasynaptic. A range of depolarizing stimuli caused GABA exocytosis, showing that extrasynaptic release of GABA is controlled by DA cell electrical activity. With all modalities of stimulation, including long-lasting square pulses, segments of pacemaker activity delivered by the action-potential-clamp method and high-frequency trains of ramps, discharge of GABAergic currents exhibited considerable variability in latency and duration, suggesting that coupling between Ca2+ influx and transmitter exocytosis is extremely loose in comparison with the synapse. Paracrine signaling based on extrasynaptic release of GABA by DA cells and other GABAergic amacrines may participate in controlling the excitability of the neuronal processes that interact synaptically in the inner plexiform layer.
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Affiliation(s)
- Hajime Hirasawa
- Department of Neurobiology, Harvard Medical School, 220 Longwood Ave., Boston, MA 02115, USA
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Nemargut JP, Zhu J, Savoie BT, Wang GY. Differential effects of charybdotoxin on the activity of retinal ganglion cells in the dark- and light-adapted mouse retina. Vision Res 2009; 49:388-97. [PMID: 19084033 PMCID: PMC2721325 DOI: 10.1016/j.visres.2008.11.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 11/12/2008] [Accepted: 11/18/2008] [Indexed: 11/29/2022]
Abstract
Patch-clamp recordings were made from retinal ganglion cells in the mouse retina. Under dark adaptation, blockage of BK(Ca) channels increases the spontaneous excitatory postsynaptic currents (EPSCs) and light-evoked On-EPSCs, while it decreases the light-evoked Off inhibitory postsynaptic currents (IPSCs). However, under light adaptation it decreases the light-evoked On-EPSCs, the spontaneous IPSCs and the light-evoked On- and Off-IPSCs. Blockage of BK(Ca) channels significantly altered the outputs of RGCs by changing their light-evoked responses into a bursting pattern and increasing the light-evoked depolarization of the membrane potentials, while it did not significantly change the peak firing rates of light-evoked responses.
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Affiliation(s)
- Joseph P Nemargut
- Department of Structural and Cellular Biology, School of Medicine, Tulane University, New Orleans, LA 70112, USA
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Abstract
Action potentials were recorded from rat retinal ganglion cell fibers in the presence of a uniform field, and the maintained discharge pattern was characterized. Spike trains recorded under ketaminexylazine. The majority of cells had multimodal interval distributions, with the first peak in the range of 25.00.97). Both ON and OFF cells show serial correlations between adjacent interspike intervals, while ON cells also showed second-order correlations. Cells with multimodal interval distribution showed a strong peak at high frequencies in the power spectra in the range of 28.9-41.4 Hz. Oscillations were present under both anesthetic conditions and persisted in the dark at a slightly lower frequency, implying that the oscillations are generated independent of any light stimulus but can be modulated by light level. The oscillation frequency varied slightly between cells of the same type and in the same eye, suggesting that multiple oscillatory generating mechanisms exist within the retina. Cells with high-frequency oscillations were described well by an integrate-and-fire model with the input consisting of Gaussian noise plus a sinusoid where the phase was jittered randomly to account for the bandwidth present in the oscillations.
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Chen H, Zhang M, Huang S, Wu D. The photopic negative response of flash ERG in nonproliferative diabetic retinopathy. Doc Ophthalmol 2008; 117:129-35. [PMID: 18214565 DOI: 10.1007/s10633-008-9114-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2007] [Accepted: 01/07/2008] [Indexed: 12/20/2022]
Abstract
PURPOSE To test how the PhNR of the flash ERG is affected in human nonproliferative diabetic retinopathy (NPDR). METHODS The PhNR was elicited with red stimuli (5 cd s/m(2) with 4-min duration) and blue background (10 cd/m(2)). Standard Ganzfeld flash ERGs were recorded according to the ISCEV standard for the clinical electroretinogram (2004). A total of 81 diabetic patients with different severity levels of NPDR were examined. Forty-three age-matched normal controls were also studied. RESULTS The amplitude of PhNR decreased significantly as DR progressed, while the implicit time was prolonged. Amplitudes of the PhNR in the control group, no DR, mild NPDR, moderate NPDR, and severe NPDR were 78.1 +/- 15.1 microV, 69.0 +/- 17.8 microV, 64.5 +/- 13.2 microV, 45.9 +/- 9.0 microV, and 33.7 +/- 10.8 muV respectively, and the implicit times of PhNR were 71.5 +/- 5.0, 72.0 +/- 6.2, 73.6 +/- 5.0, 75.7 +/- 6.1, and 82.9 +/- 7.8 min respectively. Compared to the control group, the reduction of PhNR amplitude in all diabetic groups was statistically significant. However, except for the OPs, the percent reduction of the amplitude of standard ERG waves was far less than that of the PhNR. The percent decrease in amplitude of the PhNR and summation OPs was not significantly different in any diabetic group. However, the reduction of the amplitude of summation OPs (and other standard ERG waves) was statistically significant only in moderate and severe NPDR groups. CONCLUSIONS PhNR is a sensitive indicator of the function of inner retina in diabetic patients. There is a potential role for the PhNR in assessing inner retinal damage and evaluating the effect of treatment in NPDR.
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Affiliation(s)
- Hongling Chen
- Joint Shantou International Eye Center, The Shantou University, Shantou, Guangdong, 515041, China
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Miller JA, Kenyon GT. Extracting number-selective responses from coherent oscillations in a computer model. Neural Comput 2007; 19:1766-97. [PMID: 17521279 DOI: 10.1162/neco.2007.19.7.1766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cortical neurons selective for numerosity may underlie an innate number sense in both animals and humans. We hypothesize that the number- selective responses of cortical neurons may in part be extracted from coherent, object-specific oscillations . Here, indirect evidence for this hypothesis is obtained by analyzing the numerosity information encoded by coherent oscillations in artificially generated spikes trains. Several experiments report that gamma-band oscillations evoked by the same object remain coherent, whereas oscillations evoked by separate objects are uncorrelated. Because the oscillations arising from separate objects would add in random phase to the total power summed across all stimulated neurons, we postulated that the total gamma activity, normalized by the number of spikes, should fall roughly as the square root of the number of objects in the scene, thereby implicitly encoding numerosity. To test the hypothesis, we examined the normalized gamma activity in multiunit spike trains, 50 to 1000 msec in duration, produced by a model feedback circuit previously shown to generate realistic coherent oscillations. In response to images containing different numbers of objects, regardless of their shape, size, or shading, the normalized gamma activity followed a square-root-of-n rule as long as the separation between objects was sufficiently large and their relative size and contrast differences were not too great. Arrays of winner-take-all numerosity detectors, each responding to normalized gamma activity within a particular band, exhibited tuning curves consistent with behavioral data. We conclude that coherent oscillations in principle could contribute to the number-selective responses of cortical neurons, although many critical issues await experimental resolution.
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Affiliation(s)
- Jeremy A Miller
- Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
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18
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Miller JA, Denning KS, George JS, Marshak DW, Kenyon GT. A high frequency resonance in the responses of retinal ganglion cells to rapidly modulated stimuli: a computer model. Vis Neurosci 2006; 23:779-94. [PMID: 17020633 PMCID: PMC3350093 DOI: 10.1017/s0952523806230104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 05/09/2006] [Indexed: 11/05/2022]
Abstract
Brisk Y-type ganglion cells in the cat retina exhibit a high frequency resonance (HFR) in their responses to large, rapidly modulated stimuli. We used a computer model to test whether negative feedback mediated by axon-bearing amacrine cells onto ganglion cells could account for the experimentally observed properties of HFRs. Temporal modulation transfer functions (tMTFs) recorded from model ganglion cells exhibited HFR peaks whose amplitude, width, and locations were qualitatively consistent with experimental data. Moreover, the wide spatial distribution of axon-mediated feedback accounted for the observed increase in HFR amplitude with stimulus size. Model phase plots were qualitatively similar to those recorded from Y ganglion cells, including an anomalous phase advance that in our model coincided with the amplification of low-order harmonics that overlapped the HFR peak. When axon-mediated feedback in the model was directed primarily to bipolar cells, whose synaptic output was graded, or else when the model was replaced with a simple cascade of linear filters, it was possible to produce large HFR peaks but the region of anomalous phase advance was always eliminated, suggesting the critical involvement of strongly non-linear feedback loops. To investigate whether HFRs might contribute to visual processing, we simulated high frequency ocular tremor by rapidly modulating a naturalistic image. Visual signals riding on top of the imposed jitter conveyed an enhanced representation of large objects. We conclude that by amplifying responses to ocular tremor, HFRs may selectively enhance the processing of large image features.
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Affiliation(s)
- J A Miller
- Applied Modern Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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19
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Chen H, Wu D, Huang S, Yan H. The photopic negative response of the flash electroretinogram in retinal vein occlusion. Doc Ophthalmol 2006; 113:53-9. [PMID: 16944088 DOI: 10.1007/s10633-006-9015-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 07/15/2006] [Indexed: 11/26/2022]
Abstract
The photopic negative response (PhNR) has recently been shown to be severely affected in central retinal artery occlusion (CRAO), despite relative preservation of the cone b-wave compared to that in the healthy unaffected fellow eye. The aim of this study was to test how the PhNR of the flash electroretinogram (ERG) is affected in human retinal vein occlusion. PhNR was elicited with red stimuli (1 cd s/m2, 5 cd s/m2, and 7 cd s/m2 with 4 ms duration) and blue background (10 cd/m2). Standard Ganzfeld flash ERG was produced according to the ISCEV standard for the clinical electroretinogram (2004). Sixteen patients with central retinal vein occlusion (CRVO), 14 patients with branch retinal vein occlusion (BRVO), and 16 controls were analyzed. The amplitude of the PhNRs was significantly smaller in the CRVO and BRVO eyes than those in the unaffected fellow or control eyes (p = 0.000). There was a significantly greater reduction of PhNR amplitudes than that of other waves including the OPs, rod b-wave, combined a-wave and b-wave, cone a-wave and b-wave, and 30 Hz flicker ERG. Thus, PhNR amplitude in retinal vein occlusion is severely affected. There is a potential role for PhNR in assessing inner retinal damage and evaluating the effect of treatment.
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Affiliation(s)
- Hongling Chen
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, 54 S. Xianlie Road, Guangzhou, 510060, PR China
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20
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Oliver D, Taberner AM, Thurm H, Sausbier M, Arntz C, Ruth P, Fakler B, Liberman MC. The role of BKCa channels in electrical signal encoding in the mammalian auditory periphery. J Neurosci 2006; 26:6181-9. [PMID: 16763026 PMCID: PMC1806704 DOI: 10.1523/jneurosci.1047-06.2006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Large-conductance voltage- and Ca(2+)-activated K+ channels (BKCa) are involved in shaping spiking patterns in many neurons. Less is known about their role in mammalian inner hair cells (IHCs), mechanosensory cells with unusually large BKCa currents. These currents may be involved in shaping the receptor potential, implying crucial importance for the properties of afferent auditory signals. We addressed the function of BKCa by recording sound-induced responses of afferent auditory nerve (AN) fibers from mice with a targeted deletion of the pore-forming alpha-subunit of BKCa (BKalpha(-/-)) and comparing these with voltage responses of current-clamped IHCs. BKCa-mediated currents in IHCs were selectively abolished in BKalpha(-/-), whereas cochlear physiology was essentially normal with respect to cochlear sensitivity and frequency tuning.BKalpha(-/-) AN fibers showed deteriorated precision of spike timing, measured as an increased variance of first spike latency in response to tone bursts. This impairment could be explained by a slowed voltage response in the presynaptic IHC resulting from the reduced K+ conductance in the absence of BKCa. Maximum spike rates of AN fibers were reduced nearly twofold in BKalpha(-/-), contrasting with increased voltage responses of IHCs. In addition to presynaptic changes, which may be secondary to a modest depolarization of BKalpha(-/-) IHCs, this reduction in AN rates suggests a role of BKCa in postsynaptic AN neurons, which was supported by increased refractory periods. In summary, our results indicate an essential role of IHC BKCa channels for precise timing of high-frequency cochlear signaling as well as a function of BKCa in the primary afferent neuron.
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Affiliation(s)
- Dominik Oliver
- Physiologisches Institut, Universität Freiburg, D-79104 Freiburg, Germany.
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21
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Petit-Jacques J, Völgyi B, Rudy B, Bloomfield S. Spontaneous oscillatory activity of starburst amacrine cells in the mouse retina. J Neurophysiol 2005; 94:1770-80. [PMID: 15917322 DOI: 10.1152/jn.00279.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using patch-clamp techniques, we investigated the characteristics of the spontaneous oscillatory activity displayed by starburst amacrine cells in the mouse retina. At a holding potential of -70 mV, oscillations appeared as spontaneous, rhythmic inward currents with a frequency of approximately 3.5 Hz and an average maximal amplitude of approximately 120 pA. Application of TEA, a potassium channel blocker, increased the amplitude of oscillatory currents by >70% but reduced their frequency by approximately 17%. The TEA effects did not appear to result from direct actions on starburst cells, but rather a modulation of their synaptic inputs. Oscillatory currents were inhibited by 6-cyano-7-nitroquinoxalene-2,3-dione (CNQX), an antagonist of AMPA/kainate receptors, indicating that they were dependent on a periodic glutamatergic input likely from presynaptic bipolar cells. The oscillations were also inhibited by the calcium channel blockers cadmium and nifedipine, suggesting that the glutamate release was calcium dependent. Application of AP4, an agonist of mGluR6 receptors on on-center bipolar cells, blocked the oscillatory currents in starburst cells. However, application of TEA overcame the AP4 blockade, suggesting that the periodic glutamate release from bipolar cells is intrinsic to the inner plexiform layer in that, under experimental conditions, it can occur independent of photoreceptor input. The GABA receptor antagonists picrotoxin and bicuculline enhanced the amplitude of oscillations in starburst cells prestimulated with TEA. Our results suggest that this enhancement was due to a reduction of a GABAergic feedback inhibition from amacrine cells to bipolar cells and the resultant increased glutamate release. Finally, we found that some ganglion cells and other types of amacrine cell also displayed rhythmic activity, suggesting that oscillatory behavior is expressed by a number of inner retinal neurons.
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Affiliation(s)
- Jerome Petit-Jacques
- Department of Ophthalmology, New York University School of Medicine, 550 First Ave., New York, New York 10016, USA
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22
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Bieda MC, Copenhagen DR. N-type and L-type calcium channels mediate glycinergic synaptic inputs to retinal ganglion cells of tiger salamanders. Vis Neurosci 2005; 21:545-50. [PMID: 15579220 PMCID: PMC2579891 DOI: 10.1017/s0952523804214055] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2003] [Indexed: 11/05/2022]
Abstract
Synaptically localized calcium channels shape the timecourse of synaptic release, are a prominent site for neuromodulation, and have been implicated in genetic disease. In retina, it is well established that L-type calcium channels play a major role in mediating release of glutamate from the photoreceptors and bipolar cells. However, little is known about which calcium channels are coupled to synaptic exocytosis of glycine, which is primarily released by amacrine cells. A recent report indicates that glycine release from spiking AII amacrine cells relies exclusively upon L-type calcium channels. To identify calcium channel types controlling neurotransmitter release from the population of glycinergic neurons that drive retinal ganglion cells, we recorded electrical and potassium evoked inhibitory synaptic currents (IPSCs) from these postsynaptic neurons in retinal slices from tiger salamanders. The L-channel antagonist nifedipine strongly inhibited release and FPL64176, an L-channel agonist, greatly enhanced it, indicating a significant role for L-channels. omega-Conotoxin MVIIC, an N/P/Q-channel antagonist, strongly inhibited release, indicating an important role for non-L channels. While the P/Q-channel blocker omega-Aga IVA produced only small effects, the N-channel blocker omega-conotoxin GVIA strongly inhibited release. Hence, N-type and L-type calcium channels appear to play major roles, overall, in mediating synaptic release of glycine onto retinal ganglion cells.
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Affiliation(s)
- Mark C Bieda
- Department of Ophthalmology, University of California, San Francisco, CA 94143-0730, USA
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23
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Xiao J, Cai Y, Yen J, Steffen M, Baxter DA, Feigenspan A, Marshak D. Voltage-clamp analysis and computational model of dopaminergic
neurons from mouse retina. Vis Neurosci 2005; 21:835-49. [PMID: 15733339 DOI: 10.1017/s0952523804216042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Indexed: 11/05/2022]
Abstract
Isolated dopaminergic amacrine (DA) cells in mouse retina fire
rhythmic, spontaneous action potentials and respond to depolarizing
current with trains of low-frequency action potentials. To investigate
the roles of voltage-gated ion channels in these processes, the
transient A-type K+ current (IK,A) and
Ca2+ current (ICa) in isolated mouse DA cells
were analyzed by voltage clamp. The IK,A activated at
−60 mV and inactivated rapidly. ICa activated at
around −30 mV and reached a peak at 10 mV without apparent
inactivation. We also extended our previous computational model of the
mouse DA cell to include the new electrophysiological data. The model
consisted of a membrane capacitance in parallel with eight currents:
Na+ transient (INa,T), Na+ persistent
(INa,P), delayed rectifier potassium (IKdr),
IK,A, calcium-dependent potassium (IK,Ca), L-type
Ca2+ ICa, hyperpolarization-activated cation
current (Ih), and a leak current (IL).
Hodgkin-Huxley type equations were used to define the voltage- and
time-dependent activation and inactivation. The simulations were
implemented using the neurosimulator SNNAP. The model DA cell was
spontaneously active from a wide range of initial membrane potentials.
The spontaneous action potentials reached 35 mV at the peak and
hyperpolarized to −76 mV between spikes. The spontaneous firing
frequency in the model was 6 Hz. The model DA cell responded to
prolonged depolarizing current injection by increasing its spiking
frequency and eventually reaching a depolarization block at membrane
potentials greater than −10 mV. The most important current for
determining the firing rate was IK,A. When the amplitude of
IK,A was decreased, the firing rate increased.
ICa and IK,Ca also affected the width of action
potentials but had only minor effects on the firing rate. Ih
affected the firing rate slightly but did not change the waveform of
the action potentials.
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Affiliation(s)
- Jianguo Xiao
- Department of Neurobiology and Anatomy, The University of Texas-Houston Medical School, Houston, TX 77225, USA
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24
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Torborg C, Wang CT, Muir-Robinson G, Feller MB. L-type calcium channel agonist induces correlated depolarizations in mice lacking the beta2 subunit nAChRs. Vision Res 2005; 44:3347-55. [PMID: 15536002 DOI: 10.1016/j.visres.2004.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 07/23/2004] [Indexed: 10/26/2022]
Abstract
Retinal waves are mediated in part by activation of nicotinic receptors containing the beta2 subunit. Mice deficient in beta2 containing nAChRs have maintained firing of action potentials but do not support correlated waves. As a result, beta2-/- mice have inhibited refinement of circuits within the retina as well as retinal projections to the CNS. Previously, we observed that correlated increases in calcium reminiscent of retinal waves could be induced in beta2-/- retina by pharmacological application of the L-type calcium channel agonist, FPL-64176. Here, we characterize FPL-induced activity patterns in beta2-/- retina using both whole cell and multielectrode array recordings. FPL-induced strong depolarizations in previously non-spiking beta2-/- retinal ganglion cells. Though these strong depolarizations were likely to underlie the FPL-induced calcium transients, they led to highly variable effects on the spiking of individual retinal ganglion cells. In addition, induced spiking activity had significantly weaker nearest-neighbor correlations than WT mice. Initial attempts of intraocular injections of FPL in beta2-/- mice did not rescue eye-specific layer formation. These findings indicate that activity induced by FPL is not sufficient for driving eye-specific segregation in beta2-/- mice.
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Affiliation(s)
- Christine Torborg
- Neurobiology Section 0357, Division of Biological Sciences, UCSD, 9500 Gilman Drive, La Jolla, CA 92093-0357, USA
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25
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Arai I, Yamada Y, Asaka T, Tachibana M. Light-evoked oscillatory discharges in retinal ganglion cells are generated by rhythmic synaptic inputs. J Neurophysiol 2004; 92:715-25. [PMID: 15277593 DOI: 10.1152/jn.00159.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the visual system, optimal light stimulation sometimes generates gamma-range (ca. 20 approximately 80 Hz) synchronous oscillatory spike discharges. This phenomenon is assumed to be related to perceptual integration. Applying a planar multi-electrode array to the isolated frog retina, Ishikane et al. demonstrated that dimming detectors, off-sustained type ganglion cells, generate synchronous oscillatory spike discharges in response to diffuse dimming illumination. In the present study, applying the whole cell current-clamp technique to the isolated frog retina, we examined how light-evoked oscillatory spike discharges were generated in dimming detectors. Light-evoked oscillatory ( approximately 30 Hz) spike discharges were triggered by rhythmic ( approximately 30 Hz) fluctuations superimposed on a depolarizing plateau potential. When a suprathreshold steady depolarizing current was injected into a dimming detector, only a few spikes were evoked at the stimulus onset. However, repetitive spikes were triggered by a gamma-range sinusoidal current superimposed on the steady depolarizing current. Thus the light-evoked rhythmic fluctuations are likely to be generated presynaptically. The light-evoked rhythmic fluctuations were suppressed not by intracellular application of N-(2,6-dimethyl-phenylcarbamoylmethyl)triethylammonium bromide (QX-314), a Na(+) channel blocker, to the whole cell clamped dimming detector but by bath-application of tetrodotoxin to the retina. The light-evoked rhythmic fluctuations were suppressed by a GABA(A) receptor antagonist but potentiated by a GABA(C) receptor antagonist, whereas these fluctuations were little affected by a glycine receptor antagonist. Because amacrine cells are spiking neurons and because GABA is one of the main transmitters released from amacrine cells, amacrine cells may participate in generating rhythmically fluctuated synaptic input to dimming detectors.
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Affiliation(s)
- Itaru Arai
- Dept. of Psychology, Graduate School of Humanities and Sociology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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26
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Nakajo K, Okamura Y. Development of Transient Outward Currents Coupled With Ca2+-Induced Ca2+Release Mediates Oscillatory Membrane Potential in Ascidian Muscle Cells. J Neurophysiol 2004; 92:1056-66. [PMID: 15056691 DOI: 10.1152/jn.00043.2004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Isolated ascidian Halocynthia roretzi blastomeres of the muscle lineage exhibit muscle cell-like excitability on differentiation despite the arrest of cell cleavage early in development. This characteristic provides a unique opportunity to track changes in ion channel expression during muscle cell differentiation. Here, we show that the intrinsic membrane property of ascidian cleavage-arrested muscle-type cells becomes oscillatory by expressing transient outward currents ( Ito) activated by Ca2+-induced Ca2+release (CICR) in a maturation-dependent manner. In current-clamp mode, most day 4 (72 h after fertilization) cleavage-arrested muscle cells exhibited an oscillatory membrane potential of –20 mV at 15 Hz, whereas most day 3 (48 h after fertilization) cells exhibited a spiking pattern. In voltage-clamp mode, the day 4 cells exhibited prominent transient outward currents that were not present in day 3 cells. Itowas abolished by the application of 10 mM caffeine, implying that CICR was involved in Itoactivation. Itowas based on K+efflux and sensitive to tetraethylammonium and some Ca2+-activated K+channel inhibitors. We found a 60-pS single channel conductance that was activated by local Ca2+release in ascidian muscle cell. Voltage-clamp recording with an oscillatory waveform as a command pulse showed that CICR-activated K+currents were activated during the falling phase of the membrane potential oscillation. These results suggest that developmental expression of CICR-activated K+current plays a role in the maturation of larval locomotion by modifying the intrinsic membrane excitability of muscle cells.
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Affiliation(s)
- Koichi Nakajo
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Meguro-ku, 153-8902 Tokyo, Japan.
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27
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Vigh J, Lasater EM. L-type calcium channels mediate transmitter release in isolated,
wide-field retinal amacrine cells. Vis Neurosci 2004; 21:129-34. [PMID: 15259564 DOI: 10.1017/s095252380404204x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Transmitter release in neurons is triggered by intracellular
Ca2+ increase via the opening of voltage-gated
Ca2+ channels. Here we investigated the voltage-gated
Ca2+ channels in wide-field amacrine cells (WFACs) isolated
from the white-bass retina that are functionally coupled to transmitter
release. We monitored transmitter release through the measurement of
the membrane capacitance (Cm). We found
that 500-ms long depolarizations of WFACs from −70 mV to 0 mV
elicited about a 6% transient increase in the
Cm or membrane surface area. This
Cm jump could be eliminated either by
intracellular perfusion with 10 mM BAPTA or by extracellular
application of 4 mM cobalt. WFACs possess N-type and L-type
voltage-gated Ca2+ channels. Depolarization-evoked
Cm increases were unaffected by the
specific N-type channel blocker ω-conotoxin GVIA, but they were
markedly reduced by the L-type blocker diltiazem, suggesting a role for
the L-type channel in synaptic transmission. Further supporting this
notion, in WFACs the synaptic protein syntaxin always colocalized with
the pore-forming subunit of the retinal specific L-type channels
(CaV1.4 or α1F), but never with that of the N-type
channels (CaV2.2 or α1B).
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Affiliation(s)
- Jozsef Vigh
- Department of Ophthalmology and Visual Sciences, John Moran Eye Center, University of Utah, Health Sciences Center, Salt Lake City 84132, USA
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28
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Kenyon GT, Moore B, Jeffs J, Denning KS, Stephens GJ, Travis BJ, George JS, Theiler J, Marshak DW. A model of high-frequency oscillatory potentials in retinal
ganglion cells. Vis Neurosci 2004; 20:465-80. [PMID: 14977326 PMCID: PMC3348786 DOI: 10.1017/s0952523803205010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
High-frequency oscillatory potentials (HFOPs) have been recorded from
ganglion cells in cat, rabbit, frog, and mudpuppy retina and in
electroretinograms (ERGs) from humans and other primates. However, the
origin of HFOPs is unknown. Based on patterns of tracer coupling, we
hypothesized that HFOPs could be generated, in part, by negative
feedback from axon-bearing amacrine cells excited via
electrical synapses with neighboring ganglion cells. Computer
simulations were used to determine whether such axon-mediated feedback
was consistent with the experimentally observed properties of HFOPs.
(1) Periodic signals are typically absent from ganglion cell PSTHs, in
part because the phases of retinal HFOPs vary randomly over time and
are only weakly stimulus locked. In the retinal model, this phase
variability resulted from the nonlinear properties of axon-mediated
feedback in combination with synaptic noise. (2) HFOPs increase as a
function of stimulus size up to several times the receptive-field
center diameter. In the model, axon-mediated feedback pooled signals
over a large retinal area, producing HFOPs that were similarly size
dependent. (3) HFOPs are stimulus specific. In the model, gap junctions
between neighboring neurons caused contiguous regions to become phase
locked, but did not synchronize separate regions. Model-generated HFOPs
were consistent with the receptive-field center dynamics and spatial
organization of cat alpha cells. HFOPs did not depend qualitatively on
the exact value of any model parameter or on the numerical precision of
the integration method. We conclude that HFOPs could be mediated, in
part, by circuitry consistent with known retinal anatomy.
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Affiliation(s)
- Garrett T Kenyon
- P-21, Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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