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Linn DM. Target identification and validation of the alpha7 nicotinic acetylcholine receptor as a potential therapeutic target in retinal disease. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1190439. [PMID: 38983049 PMCID: PMC11182235 DOI: 10.3389/fopht.2023.1190439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 05/26/2023] [Indexed: 07/11/2024]
Abstract
The role of acetylcholine (ACh) in visual processing in the mammalian retina has been the focus of research for many decades. Pioneering work on the localization of ACh discovered that the neurotransmitter is synthesized and stored in a distinct subpopulation of amacrine (starburst) cells. It has been shown that ACh release is regulated to a low resting "tonic" level, much like what is observed at the neuromuscular junction (NMJ). If there were a dysfunction in the tonic release of ACh, might post-synaptic changes render the targets of ACh [i.e., retinal ganglion cells (RGCs)] vulnerable to disease? During my time at Pharmacia & Upjohn (PNU), selective nicotinic ACh receptor (nAChR) agonists (e.g., PNU-282987) were developed as a possible therapy for central nervous system (CNS) diseases. As RGCs are the main targets of neurodegeneration in glaucoma, could the activation of this target provide neuroprotection? In response to this question, experiments to identify alpha7 nAChRs in the retina (i.e., target ID studies) followed by "proof-of-concept" experiments were conducted. Target ID studies included binding studies with retinal homogenates, [125I]-alpha-bungarotoxin (α-BTX) autoradiography, and fluorescently tagged α-BTX binding in retinal slices. Imaging studies of intracellular calcium dynamics in the retinal slice were conducted. Reverse transcription-polymerase chain reaction (RT-PCR) analysis with alpha7 nAChR knockout mice using the "laser-capture microdissection" technique, in situ hybridization studies, and RT-PCR analysis of the human retina were conducted. Collectively, these experiments confirmed the presence of alpha7 nAChRs on specific cells in the retina. "Proof-of-concept" neuroprotection studies demonstrated that PNU-282987 provided significant protection for RGCs. This protection was dose dependent and was blocked with selective antagonists. More recently, evidence for the generation of new RGCs has been reported with PNU-282987 in rodents. Interestingly, the appearance of new RGCs is more pronounced with eye-drop application than with intravitreal injection. One could postulate that this reflects the neurogenic activation of alpha7 receptors on the retinal pigment epithelium (RPE) (eye drops) vs. a neuroprotective effect on RGCs (injections). In conclusion, there does appear to be a cholinergic retinal "tone" associated with RGCs that could be utilized as a neuroprotective therapy. However, a distinct cholinergic neurogenic mechanism also appears to exist in the outer retina that could possibly be exploited to generate new RGCs lost through various disease processes.
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Affiliation(s)
- David M Linn
- Department of Biomedical Sciences, Grand Valley State University, Allendale, MI, United States
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2
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Qi W, Fu H, Luo X, Ren Y, Liu X, Dai H, Zheng Q, Liang F. Electroacupuncture at PC6 (Neiguan) Attenuates Angina Pectoris in Rats with Myocardial Ischemia-Reperfusion Injury Through Regulating the Alternative Splicing of the Major Inhibitory Neurotransmitter Receptor GABRG2. J Cardiovasc Transl Res 2022; 15:1176-1191. [PMID: 35377129 DOI: 10.1007/s12265-022-10245-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 03/25/2022] [Indexed: 11/27/2022]
Abstract
Angina pectoris is the most common manifestation of coronary heart disease, causing suffering in patients. Electroacupuncture at PC6 can effectively alleviate angina by regulating the expression of genes, whether the alternative splicing (AS) of genes is affected by acupuncture is still unknown. We established a rat model of myocardial ischemia-reperfusion by coronary artery ligation and confirmed electroacupuncture alleviated the abnormal discharge caused by angina pectoris measured in EMG electromyograms. Analysis of the GSE61840 dataset established that AS events were altered after I/R and regulated by electroacupuncture. I/R decreased the expression of splicing factor Nova1 while electroacupuncture rescued it. Further experiments in dorsal root ganglion cells showed Nova1 regulated the AS of the GABRG2, specifically on its exon 9 where an important phosphorylation site is present. In vivo, results also showed that electroacupuncture can restore AS of GABRG2. Our results proved that electroacupuncture alleviates angina results by regulating alternative splicing.
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Affiliation(s)
- Wenchuan Qi
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China
| | - Hongjuan Fu
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China
| | - Xinye Luo
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China
| | - Yanrong Ren
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China.,Shanxi University of Traditional Chinese Medicine, Jinzhong, 030002, Shanxi, China
| | - Xueying Liu
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China.,Shanxi University of Traditional Chinese Medicine, Jinzhong, 030002, Shanxi, China
| | - Hongyuan Dai
- College of Life Sciences, Sichuan University, Chengdu, 610065, Sichuan, China
| | - Qianhua Zheng
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China
| | - Fanrong Liang
- Chengdu University of Traditional Chinese Medicine, Chengdu, 610075, Sichuan, China.
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3
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Eliasen JN, Krall J, Frølund B, Kohlmeier KA. Sex-specific alterations in GABA receptor-mediated responses in laterodorsal tegmentum are associated with prenatal exposure to nicotine. Dev Neurobiol 2020; 80:178-199. [PMID: 32628361 DOI: 10.1002/dneu.22772] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/23/2020] [Accepted: 06/23/2020] [Indexed: 12/14/2022]
Abstract
Smoking during pregnancy is associated with deleterious physiological and cognitive effects on the offspring, which are likely due to nicotine-induced alteration in the development of neurotransmitter systems. Prenatal nicotine exposure (PNE) in rodents is associated with changes in behaviors controlled in part by the pontine laterodorsal tegmentum (LDT), and LDT excitatory signaling is altered in a sex and age-dependent manner by PNE. As effects on GABAergic LDT signaling are unknown, we used calcium imaging to evaluate GABAA receptor- (GABAA R as well as GABAA -ρ R) and GABAB receptor (GABAB R)-mediated calcium responses in LDT brain slices from female and male PNE mice in two different age groups. Overall, in older PNE females, changes in calcium induced by stimulation of GABAA R and GABAB R, including GABAA -ρ R were shifted toward calcium rises. In both young and old males, PNE was associated with alterations in calcium mediated by all three receptors; however, the GABAA R was the most affected. These results show for the first time that PNE is associated with alterations in GABAergic transmission in the LDT in a sex- and age-dependent manner, and these data are the first to show PNE-associated alterations in functionality of GABA receptors in any nucleus. PNE-associated alterations in LDT GABAergic transmission within the LDT would be expected to alter output to target regions and could play a role in LDT-implicated, negative behavioral outcomes following gestational exposure to smoking. Accordingly, our data provide further supportive evidence of the importance of eliminating the consumption of nicotine during pregnancy.
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Affiliation(s)
- Jannik Nicklas Eliasen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Krall
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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4
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Simulated Saccadic Stimuli Suppress ON-Type Direction-Selective Retinal Ganglion Cells via Glycinergic Inhibition. J Neurosci 2019; 39:4312-4322. [PMID: 30926751 DOI: 10.1523/jneurosci.3066-18.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 03/18/2019] [Accepted: 03/19/2019] [Indexed: 02/06/2023] Open
Abstract
Two types of mammalian direction-selective ganglion cells (DSGCs), ON and ONOFF, operate over different speed ranges. The directional axes of the ON-DSGCs are thought to align with the axes of the vestibular system and provide sensitivity at rotational velocities that are too slow to activate the semicircular canals. ONOFF-DSGCs respond to faster image velocities. Using natural images that simulate the natural visual inputs to freely moving animals, we show that simulated visual saccades suppress responses in ON-DSGCs but not ONOFF-DSGCs recorded in retinas of domestic rabbits of either gender. Analysis of the synaptic inputs shows that this saccadic suppression results from glycinergic inputs that are specific to ON-DSGCs and are absent in ONOFF-DSGCs. When this glycinergic input is blocked, both cell types respond similarly to visual saccades and display essentially identical speed tuning. The results demonstrate that glycinergic circuits within the retina can produce saccadic suppression of retinal ganglion cell activity. The cell-type-specific targeting of the glycinergic circuits further supports the proposed physiological roles of ON-DSGCs in retinal-image stabilization and of ONOFF-DSGCs in detecting local object motion and signaling optical flow.SIGNIFICANCE STATEMENT In the mammalian retina, ON direction-selective ganglion cells (DSGCs) respond preferentially to slow image motion, whereas ONOFF-DSGCs respond better to rapid motion. The mechanisms producing this different speed tuning remain unclear. Here we show that simulated visual saccades suppress ON-DSGCs, but not ONOFF-DSGCs. This selective saccadic suppression is because of the selective targeting of glycinergic inhibitory synaptic inputs to ON-DSGCs. The different saccadic suppression in the two cell types points to different physiological roles, consistent with their projections to distinct areas within the brain. ON-DSGCs may be critical for providing the visual feedback signals that contribute to stabilizing the image on the retina, whereas ONOFF-DSGCs may be important for detecting the onset of saccades or for signaling optical flow.
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5
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Dendro-dendritic cholinergic excitation controls dendritic spike initiation in retinal ganglion cells. Nat Commun 2017; 8:15683. [PMID: 28589928 PMCID: PMC5477517 DOI: 10.1038/ncomms15683] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 04/12/2017] [Indexed: 02/06/2023] Open
Abstract
The retina processes visual images to compute features such as the direction of image motion. Starburst amacrine cells (SACs), axonless feed-forward interneurons, are essential components of the retinal direction-selective circuitry. Recent work has highlighted that SAC-mediated dendro-dendritic inhibition controls the action potential output of direction-selective ganglion cells (DSGCs) by vetoing dendritic spike initiation. However, SACs co-release GABA and the excitatory neurotransmitter acetylcholine at dendritic sites. Here we use direct dendritic recordings to show that preferred direction light stimuli evoke SAC-mediated acetylcholine release, which powerfully controls the stimulus sensitivity, receptive field size and action potential output of ON-DSGCs by acting as an excitatory drive for the initiation of dendritic spikes. Consistent with this, paired recordings reveal that the activation of single ON-SACs drove dendritic spike generation, because of predominate cholinergic excitation received on the preferred side of ON-DSGCs. Thus, dendro-dendritic release of neurotransmitters from SACs bi-directionally gate dendritic spike initiation to control the directionally selective action potential output of retinal ganglion cells. Neural computations performed by the retinal microcircuit have been extensively studied. Here the authors report using dendritic recordings that the direction selective responses of retinal ganglion cells are controlled by dendro-dendritic cholinergic excitation from starburst amacrine cells.
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Abstract
Abstract
How direction of image motion is detected as early as at the level of the vertebrate eye has been intensively studied in retina research. Although the first direction-selective (DS) retinal ganglion cells were already described in the 1960s and have since then been in the focus of many studies, scientists are still puzzled by the intricacy of the neuronal circuits and computational mechanisms underlying retinal direction selectivity. The fact that the retina can be easily isolated and studied in a Petri dish-by presenting light stimuli while recording from the various cell types in the retinal circuits-in combination with the extensive anatomical, molecular and physiological knowledge about this part of the brain presents a unique opportunity for studying this intriguing visual circuit in detail. This article provides a brief overview of the history of research on retinal direction selectivity, but then focuses on the past decade and the progress achieved, in particular driven by methodological advances in optical recording techniques, molecular genetics approaches and large-scale ultrastructural reconstructions. As it turns out, retinal direction selectivity is a complex, multi-tiered computation, involving dendrite-intrinsic mechanisms as well as several types of network interactions on the basis of highly selective, likely genetically predetermined synaptic connectivity. Moreover, DS ganglion cell types appear to be more diverse than previously thought, differing not only in their preferred direction and response polarity, but also in physiology, DS mechanism, dendritic morphology and, importantly, the target area of their projections in the brain.
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7
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Abstract
UNLABELLED Neurons that signal the orientation of edges within the visual field have been widely studied in primary visual cortex. Much less is known about the mechanisms of orientation selectivity that arise earlier in the visual stream. Here we examine the synaptic and morphological properties of a subtype of orientation-selective ganglion cell in the rabbit retina. The receptive field has an excitatory ON center, flanked by excitatory OFF regions, a structure similar to simple cell receptive fields in primary visual cortex. Examination of the light-evoked postsynaptic currents in these ON-type orientation-selective ganglion cells (ON-OSGCs) reveals that synaptic input is mediated almost exclusively through the ON pathway. Orientation selectivity is generated by larger excitation for preferred relative to orthogonal stimuli, and conversely larger inhibition for orthogonal relative to preferred stimuli. Excitatory orientation selectivity arises in part from the morphology of the dendritic arbors. Blocking GABAA receptors reduces orientation selectivity of the inhibitory synaptic inputs and the spiking responses. Negative contrast stimuli in the flanking regions produce orientation-selective excitation in part by disinhibition of a tonic NMDA receptor-mediated input arising from ON bipolar cells. Comparison with earlier studies of OFF-type OSGCs indicates that diverse synaptic circuits have evolved in the retina to detect the orientation of edges in the visual input. SIGNIFICANCE STATEMENT A core goal for visual neuroscientists is to understand how neural circuits at each stage of the visual system extract and encode features from the visual scene. This study documents a novel type of orientation-selective ganglion cell in the retina and shows that the receptive field structure is remarkably similar to that of simple cells in primary visual cortex. However, the data indicate that, unlike in the cortex, orientation selectivity in the retina depends on the activity of inhibitory interneurons. The results further reveal the physiological basis for feature detection in the visual system, elucidate the synaptic mechanisms that generate orientation selectivity at an early stage of visual processing, and illustrate a novel role for NMDA receptors in retinal processing.
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8
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Garaycochea J, Slaughter MM. GABAB receptors enhance excitatory responses in isolated rat retinal ganglion cells. J Physiol 2016; 594:5543-54. [PMID: 27112134 DOI: 10.1113/jp272374] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/21/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS GABA is an inhibitory transmitter but can sometimes produce paradoxical excitatory effects through synaptic networks. We found a novel GABA-mediated excitation within a single retinal cell. It involves a chain of events from receptor stimulation to the sequential modulation of two associated channels, resulting in enhanced neuroexcitability. GABAB receptor activation selectively suppresses N-type calcium channels. The BK-type potassium channels are exclusively linked to the N-type calcium channel. Thus, stimulation of GABAB receptors suppresses an outward current, increasing the excitatory range of single neurons. ABSTRACT GABAB receptors (GABAB Rs) suppress voltage-gated calcium channels and activate G-protein coupled potassium channels (GIRK and TREK channels), both mechanisms serving to inhibit neurons. In isolated rat retinal spiking neurons, GABAB Rs produce both actions but the net effect is to enhance excitatory signals. This is because GABAB Rs selectively suppress N-type calcium channels, which in turn are specifically linked to BK channels. Consequently, when GABAB Rs are stimulated there is a reduction in outward current, allowing neurons to extend their level of depolarization. Whereas many retinal neurons use L-type channels to stimulate vesicle fusion, the suppression of N-type channels augments dynamic range without affecting transmitter release.
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Affiliation(s)
- Jay Garaycochea
- Neuroscience Program and Department of Physiology & Biophysics, University at Buffalo School of Medicine, 124 Sherman Hall Buffalo, NY, 14214, USA.,Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
| | - Malcolm M Slaughter
- Neuroscience Program and Department of Physiology & Biophysics, University at Buffalo School of Medicine, 124 Sherman Hall Buffalo, NY, 14214, USA.
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9
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Sigal YM, Speer CM, Babcock HP, Zhuang X. Mapping Synaptic Input Fields of Neurons with Super-Resolution Imaging. Cell 2015; 163:493-505. [PMID: 26435106 PMCID: PMC4733473 DOI: 10.1016/j.cell.2015.08.033] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 07/22/2015] [Accepted: 08/12/2015] [Indexed: 01/28/2023]
Abstract
As a basic functional unit in neural circuits, each neuron integrates input signals from hundreds to thousands of synapses. Knowledge of the synaptic input fields of individual neurons, including the identity, strength, and location of each synapse, is essential for understanding how neurons compute. Here, we developed a volumetric super-resolution reconstruction platform for large-volume imaging and automated segmentation of neurons and synapses with molecular identity information. We used this platform to map inhibitory synaptic input fields of On-Off direction-selective ganglion cells (On-Off DSGCs), which are important for computing visual motion direction in the mouse retina. The reconstructions of On-Off DSGCs showed a GABAergic, receptor subtype-specific input field for generating direction selective responses without significant glycinergic inputs for mediating monosynaptic crossover inhibition. These results demonstrate unique capabilities of this super-resolution platform for interrogating neural circuitry.
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Affiliation(s)
- Yaron M Sigal
- Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Colenso M Speer
- Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Hazen P Babcock
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Xiaowei Zhuang
- Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA; Center for Brain Science, Harvard University, Cambridge, MA 02138, USA; Department of Physics, Harvard University, Cambridge, MA 02138, USA.
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10
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Pinsky E, Donchin O, Segev R. Pharmacological study of direction selectivity in the archer fish retina. J Integr Neurosci 2015; 14:1550024. [PMID: 26380942 DOI: 10.1142/s0219635215500247] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Direction selective cells have been found in the retina, the first level of the visual system, in mammals and recently also in the archer fish. These cells are involved in a variety of fast neural computation processes, from the control of eye movements to the detection of prey by the archer fish. The standard model for this mechanism in mammalian retina is well understood and is based on the asymmetry of inhibitory and excitatory inputs to the retinal ganglion cells. However, it remains unclear whether the mechanism that underlies direction selectivity is similar across animal classes. This study reports a pharmacological investigation designed to elucidate the mechanism that underlies motion detection in the archer fish retina. Direction selectivity in the retina was characterized under the influence of specific channel blockers that are known to be present in the different types of neurons of the retina. The results show that the direction-selective mechanism in the archer fish retina is modified only when the inhibitory channels of GABA and Glycine are manipulated. This suggests that the mechanism of direction selectivity in the archer fish retina is fundamentally different from the mechanism of direction selectivity in the mammalian retina.
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Affiliation(s)
- Ehud Pinsky
- * Department of Biomedical Engineering, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
- † Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
| | - Opher Donchin
- * Department of Biomedical Engineering, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
- † Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
- ‡ Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
| | - Ronen Segev
- † Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
- § Department of Life Sciences, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel
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11
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Popova E. GABAergic neurotransmission and retinal ganglion cell function. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2015; 201:261-83. [PMID: 25656810 DOI: 10.1007/s00359-015-0981-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 01/19/2015] [Accepted: 01/21/2015] [Indexed: 01/13/2023]
Abstract
Ganglion cells are the output retinal neurons that convey visual information to the brain. There are ~20 different types of ganglion cells, each encoding a specific aspect of the visual scene as spatial and temporal contrast, orientation, direction of movement, presence of looming stimuli; etc. Ganglion cell functioning depends on the intrinsic properties of ganglion cell's membrane as well as on the excitatory and inhibitory inputs that these cells receive from other retinal neurons. GABA is one of the most abundant inhibitory neurotransmitters in the retina. How it modulates the activity of different types of ganglion cells and what is its significance in extracting the basic features from visual scene are questions with fundamental importance in visual neuroscience. The present review summarizes current data concerning the types of membrane receptors that mediate GABA action in proximal retina; the effects of GABA and its antagonists on the ganglion cell light-evoked postsynaptic potentials and spike discharges; the action of GABAergic agents on centre-surround organization of the receptive fields and feature related ganglion cell activity. Special emphasis is put on the GABA action regarding the ON-OFF and sustained-transient ganglion cell dichotomy in both nonmammalian and mammalian retina.
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Affiliation(s)
- E Popova
- Department of Physiology, Medical Faculty, Medical University, 1431, Sofia, Bulgaria,
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12
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Excitatory synaptic inputs to mouse on-off direction-selective retinal ganglion cells lack direction tuning. J Neurosci 2014; 34:3976-81. [PMID: 24623775 DOI: 10.1523/jneurosci.5017-13.2014] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Direction selectivity represents a fundamental visual computation. In mammalian retina, On-Off direction-selective ganglion cells (DSGCs) respond strongly to motion in a preferred direction and weakly to motion in the opposite, null direction. Electrical recordings suggested three direction-selective (DS) synaptic mechanisms: DS GABA release during null-direction motion from starburst amacrine cells (SACs) and DS acetylcholine and glutamate release during preferred direction motion from SACs and bipolar cells. However, evidence for DS acetylcholine and glutamate release has been inconsistent and at least one bipolar cell type that contacts another DSGC (On-type) lacks DS release. Here, whole-cell recordings in mouse retina showed that cholinergic input to On-Off DSGCs lacked DS, whereas the remaining (glutamatergic) input showed apparent DS. Fluorescence measurements with the glutamate biosensor intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) conditionally expressed in On-Off DSGCs showed that glutamate release in both On- and Off-layer dendrites lacked DS, whereas simultaneously recorded excitatory currents showed apparent DS. With GABA-A receptors blocked, both iGluSnFR signals and excitatory currents lacked DS. Our measurements rule out DS release from bipolar cells onto On-Off DSGCs and support a theoretical model suggesting that apparent DS excitation in voltage-clamp recordings results from inadequate voltage control of DSGC dendrites during null-direction inhibition. SAC GABA release is the apparent sole source of DS input onto On-Off DSGCs.
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13
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Kim HJ, Jeon CJ. Synaptic pattern of nicotinic acetylcholine receptor α7 and β2 subunits on the direction-selective retinal ganglion cells in the postnatal mouse retina. Exp Eye Res 2014; 122:54-64. [PMID: 24631336 DOI: 10.1016/j.exer.2014.02.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/18/2014] [Accepted: 02/25/2014] [Indexed: 11/26/2022]
Abstract
Direction-selective retinal ganglion cells (DS RGCs) respond strongly to a stimulus that moves in their preferred direction, but respond weakly or do not respond to a stimulus that moves in the opposite or null direction. DS RGCs are sensitive to acetylcholine, and starburst amacrine cells (SACs) make cholinergic synapses on DS RGCs. We studied the distributions of nicotinic acetylcholine receptor (nAChR) α7 and β2 subunits on the dendritic arbors of DS RGCs to search for anisotropies that contribute to the directional preferences of DS RGCs. The DS RGCs from the retinas of postnatal mice (postnatal day P5, P10, and P15) were injected with Lucifer yellow, and injected cells were identified by their dendritic morphology. The dendrites of the DS RGCs were labeled with antibodies for either the nAChR α7 or β2 subunit as well as postsynaptic density protein-95 (PSD-95), visualized by confocal microscopy, and reconstructed from high-resolution confocal images. The distribution of nAChR subunits on the dendritic arbors in both the ON and OFF layers of the RGCs revealed an asymmetrical pattern on early postnatal day P5. However, the distributions of nAChR subunits on the dendritic arbors were not asymmetric on P10 and P15. Our results therefore provide anatomical and developmental evidence suggesting that the nAChR α7 and β2 subunits may involve in the early direction-selectivity formation of DS RGCs in the mouse retina.
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Affiliation(s)
- Hyun Jin Kim
- Department of Biology, School of Life Sciences, KNU Creative BioResearch Group (BK21 Plus Program), College of Natural Sciences, and Brain Science and Engineering Institute, Kyungpook National University, Daegu 702-701, South Korea; Department of Life Sciences, Pohang University of Science and Technology, Pohang, Kyungpook 790-784, South Korea
| | - Chang Jin Jeon
- Department of Biology, School of Life Sciences, KNU Creative BioResearch Group (BK21 Plus Program), College of Natural Sciences, and Brain Science and Engineering Institute, Kyungpook National University, Daegu 702-701, South Korea.
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14
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Escobar MJ, Pezo D, Orio P. Mathematical analysis and modeling of motion direction selectivity in the retina. ACTA ACUST UNITED AC 2013; 107:349-59. [PMID: 24008129 DOI: 10.1016/j.jphysparis.2013.08.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 07/31/2013] [Accepted: 08/20/2013] [Indexed: 10/26/2022]
Abstract
Motion detection is one of the most important and primitive computations performed by our visual system. Specifically in the retina, ganglion cells producing motion direction-selective responses have been addressed by different disciplines, such as mathematics, neurophysiology and computational modeling, since the beginnings of vision science. Although a number of studies have analyzed theoretical and mathematical considerations for such responses, a clear picture of the underlying cellular mechanisms is only recently emerging. In general, motion direction selectivity is based on a non-linear asymmetric computation inside a receptive field differentiating cell responses between preferred and null direction stimuli. To what extent can biological findings match these considerations? In this review, we outline theoretical and mathematical studies of motion direction selectivity, aiming to map the properties of the models onto the neural circuitry and synaptic connectivity found in the retina. Additionally, we review several compartmental models that have tried to fill this gap. Finally, we discuss the remaining challenges that computational models will have to tackle in order to fully understand the retinal motion direction-selective circuitry.
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Affiliation(s)
- María-José Escobar
- Universidad Técnica Federico Santa María, Department of Electronics Engineering, Avda España 1680, Valparaíso, Chile
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15
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Rivlin-Etzion M, Wei W, Feller MB. Visual stimulation reverses the directional preference of direction-selective retinal ganglion cells. Neuron 2013; 76:518-25. [PMID: 23141064 DOI: 10.1016/j.neuron.2012.08.041] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 08/31/2012] [Indexed: 11/16/2022]
Abstract
Direction selectivity in the retina is mediated by direction-selective ganglion cells. These cells are part of a circuit in which they are asymmetrically wired to inhibitory neurons. Thus, they respond strongly to an image moving in the preferred direction and weakly to an image moving in the opposite (null) direction. Here, we demonstrate that adaptation with short visual stimulation of a direction-selective ganglion cell using drifting gratings can reverse this cell's directional preference by 180°. This reversal is robust, long lasting, and independent of the animal's age. Our findings indicate that, even within circuits that are hardwired, the computation of direction can be altered by dynamic circuit mechanisms that are guided by visual stimulation.
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Affiliation(s)
- Michal Rivlin-Etzion
- Department of Molecular and Cell Biology and the Helen Wills Neurosciences Institute, UC Berkeley, Berkeley, CA 94720, USA
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Auferkorte ON, Baden T, Kaushalya SK, Zabouri N, Rudolph U, Haverkamp S, Euler T. GABA(A) receptors containing the α2 subunit are critical for direction-selective inhibition in the retina. PLoS One 2012; 7:e35109. [PMID: 22506070 PMCID: PMC3323634 DOI: 10.1371/journal.pone.0035109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/13/2012] [Indexed: 01/08/2023] Open
Abstract
Far from being a simple sensor, the retina actively participates in processing visual signals. One of the best understood aspects of this processing is the detection of motion direction. Direction-selective (DS) retinal circuits include several subtypes of ganglion cells (GCs) and inhibitory interneurons, such as starburst amacrine cells (SACs). Recent studies demonstrated a surprising complexity in the arrangement of synapses in the DS circuit, i.e. between SACs and DS ganglion cells. Thus, to fully understand retinal DS mechanisms, detailed knowledge of all synaptic elements involved, particularly the nature and localization of neurotransmitter receptors, is needed. Since inhibition from SACs onto DSGCs is crucial for generating retinal direction selectivity, we investigate here the nature of the GABA receptors mediating this interaction. We found that in the inner plexiform layer (IPL) of mouse and rabbit retina, GABA(A) receptor subunit α2 (GABA(A)R α2) aggregated in synaptic clusters along two bands overlapping the dendritic plexuses of both ON and OFF SACs. On distal dendrites of individually labeled SACs in rabbit, GABA(A)R α2 was aligned with the majority of varicosities, the cell's output structures, and found postsynaptically on DSGC dendrites, both in the ON and OFF portion of the IPL. In GABA(A)R α2 knock-out (KO) mice, light responses of retinal GCs recorded with two-photon calcium imaging revealed a significant impairment of DS responses compared to their wild-type littermates. We observed a dramatic drop in the proportion of cells exhibiting DS phenotype in both the ON and ON-OFF populations, which strongly supports our anatomical findings that α2-containing GABA(A)Rs are critical for mediating retinal DS inhibition. Our study reveals for the first time, to the best of our knowledge, the precise functional localization of a specific receptor subunit in the retinal DS circuit.
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Vaney DI, Sivyer B, Taylor WR. Direction selectivity in the retina: symmetry and asymmetry in structure and function. Nat Rev Neurosci 2012; 13:194-208. [PMID: 22314444 DOI: 10.1038/nrn3165] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Visual information is processed in the retina to a remarkable degree before it is transmitted to higher visual centres. Several types of retinal ganglion cells (the output neurons of the retina) respond preferentially to image motion in a particular direction, and each type of direction-selective ganglion cell (DSGC) is comprised of multiple subtypes with different preferred directions. The direction selectivity of the cells is generated by diverse mechanisms operating within microcircuits that rely on independent neuronal processing in individual dendrites of both the DSGCs and the presynaptic neurons that innervate them.
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Affiliation(s)
- David I Vaney
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland 4072, Australia.
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18
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Borst A, Euler T. Seeing Things in Motion: Models, Circuits, and Mechanisms. Neuron 2011; 71:974-94. [PMID: 21943597 DOI: 10.1016/j.neuron.2011.08.031] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2011] [Indexed: 12/31/2022]
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19
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Cheng ZY, Chebib M, Schmid KL. rho1 GABAC receptors are expressed in fibrous and cartilaginous layers of chick sclera and located on sclera fibroblasts and chondrocytes. J Neurochem 2011; 118:281-7. [DOI: 10.1111/j.1471-4159.2011.07300.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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20
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POZNANSKI RR. CELLULAR INHIBITORY BEHAVIOR UNDERLYING THE FORMATION OF RETINAL DIRECTION SELECTIVITY IN THE STARBURST NETWORK. J Integr Neurosci 2010; 9:299-335. [DOI: 10.1142/s0219635210002457] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 08/26/2010] [Indexed: 11/18/2022] Open
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21
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Leung CKS, Yeung CK, Chiang SWY, Chan KP, Pang CP, Lam DSC. GABAAand GABAC(GABAA0r) Receptors Affect Ocular Growth and Form-Deprivation Myopia. Cutan Ocul Toxicol 2008. [DOI: 10.1081/cus-200068620] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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22
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Strang CE, Renna JM, Amthor FR, Keyser KT. Nicotinic acetylcholine receptor expression by directionally selective ganglion cells. Vis Neurosci 2007; 24:523-33. [PMID: 17686198 DOI: 10.1017/s0952523807070435] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2006] [Accepted: 04/25/2007] [Indexed: 11/06/2022]
Abstract
Acetylcholine (ACh) enhances the preferred direction responses of directionally selective ganglion cells (DS GCs; Ariel & Daw, 1982; Ariel & Adolph, 1985) through the activation of nicotinic acetylcholine receptors (nAChRs; Ariel & Daw, 1982; Massey et al., 1997; Kittila & Massey, 1997). DS GCs appear to express at least two types of nAChRs, those that are sensitive to the partially subtype-specific antagonist methyllycaconitine (MLA), and those that are MLA-insensitive (Reed et al., 2002). Our purpose was to confirm the expression of alpha7 nAChRs by DS GCs and to assess the contributions of other nAChR subtypes to DS GC responses. Using choline as a nAChR partially subtype-specific agonist, we found that the majority of DS GCs demonstrated responses to choline while under synaptic blockade. The blockade or reduction of choline-induced responses by bath application of nanomolar (nM) concentrations of MLA provided direct evidence that the choline responses were mediated by alpha7 nAChRs. Because choline is a partial agonist for alpha3beta4 nAChRs (Alkondon et al., 1997), the residual choline responses are consistent with mediation by alpha3beta4 nAChRs. Additionally, a subset of DS GCs responded to nicotine but not to choline, indicating the expression of a third nAChR subtype. The pharmacological results were supported by single cell reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry experiments. The expression of alpha7 and specific non-alpha7 nAChR subtypes was correlated with the preferred direction. This indicates the possibility of differential responses to ACh depending on the direction of movement. This is the first description of differential expression of multiple nAChR subtypes by DS GCs.
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Affiliation(s)
- Christianne E Strang
- Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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23
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Hausselt SE, Euler T, Detwiler PB, Denk W. A dendrite-autonomous mechanism for direction selectivity in retinal starburst amacrine cells. PLoS Biol 2007; 5:e185. [PMID: 17622194 PMCID: PMC1906843 DOI: 10.1371/journal.pbio.0050185] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 05/15/2007] [Indexed: 11/18/2022] Open
Abstract
Detection of image motion direction begins in the retina, with starburst amacrine cells (SACs) playing a major role. SACs generate larger dendritic Ca(2+) signals when motion is from their somata towards their dendritic tips than for motion in the opposite direction. To study the mechanisms underlying the computation of direction selectivity (DS) in SAC dendrites, electrical responses to expanding and contracting circular wave visual stimuli were measured via somatic whole-cell recordings and quantified using Fourier analysis. Fundamental and, especially, harmonic frequency components were larger for expanding stimuli. This DS persists in the presence of GABA and glycine receptor antagonists, suggesting that inhibitory network interactions are not essential. The presence of harmonics indicates nonlinearity, which, as the relationship between harmonic amplitudes and holding potential indicates, is likely due to the activation of voltage-gated channels. [Ca(2+)] changes in SAC dendrites evoked by voltage steps and monitored by two-photon microscopy suggest that the distal dendrite is tonically depolarized relative to the soma, due in part to resting currents mediated by tonic glutamatergic synaptic input, and that high-voltage-activated Ca(2+) channels are active at rest. Supported by compartmental modeling, we conclude that dendritic DS in SACs can be computed by the dendrites themselves, relying on voltage-gated channels and a dendritic voltage gradient, which provides the spatial asymmetry necessary for direction discrimination.
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Affiliation(s)
- Susanne E Hausselt
- Department of Biomedical Optics, Max-Planck Institute for Medical Research, Heidelberg, Germany
| | - Thomas Euler
- Department of Biomedical Optics, Max-Planck Institute for Medical Research, Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail:
| | - Peter B Detwiler
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Winfried Denk
- Department of Biomedical Optics, Max-Planck Institute for Medical Research, Heidelberg, Germany
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Grzywacz NM, Zucker CL. Modeling Starburst cells' GABA(B) receptors and their putative role in motion sensitivity. Biophys J 2006; 91:473-86. [PMID: 16648160 PMCID: PMC1483088 DOI: 10.1529/biophysj.105.072256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Accepted: 04/10/2006] [Indexed: 11/18/2022] Open
Abstract
Neal and Cunningham (Neal, M. J., and J. R. Cunningham. 1995. J. Physiol. (Lond.). 482:363-372) showed that GABA(B) agonists and glycinergic antagonists enhance the light-evoked release of retinal acetylcholine. They proposed that glycinergic cells inhibit the cholinergic Starburst amacrine cells and are in turn inhibited by GABA through GABA(B) receptors. However, as recently shown, glycinergic cells do not appear to have GABA(B) receptors. In contrast, the Starburst amacrine cell has GABA(B) receptors in a subpopulation of its varicosities. We thus propose an alternate model in which GABA(B)-receptor activation reduces the release of ACh from some dendritic compartments onto a glycinergic cell, which then feeds back and inhibits the Starburst cell. In this model, the GABA necessary to make these receptors active comes from the Starburst cell itself, making them autoreceptors. Computer simulations of this model show that it accounts quantitatively for the Neal and Cunningham data. We also argue that GABA(B) receptors could work to increase the sensitivity to motion over other stimuli.
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Affiliation(s)
- Norberto M Grzywacz
- Department of Biomedical Engineering, Neuroscience Graduate Program, and Center For Visual Science and Technology, University of Southern California, Los Angeles, California, USA.
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25
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Oesch N, Euler T, Taylor WR. Direction-selective dendritic action potentials in rabbit retina. Neuron 2005; 47:739-50. [PMID: 16129402 DOI: 10.1016/j.neuron.2005.06.036] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 05/31/2005] [Accepted: 06/28/2005] [Indexed: 11/16/2022]
Abstract
Dendritic spikes that propagate toward the soma are well documented, but their physiological role remains uncertain. Our in vitro patch-clamp recordings and two-photon calcium imaging show that direction-selective retinal ganglion cells (DSGCs) utilize orthograde dendritic spikes during physiological activity. DSGCs signal the direction of image motion. Excitatory subthreshold postsynaptic potentials are observed in DSGCs for motion in all directions and provide a weakly tuned directional signal. However, spikes are generated over only a narrow range of motion angles, indicating that spike generation greatly enhances directional tuning. Our results indicate that spikes are initiated at multiple sites within the dendritic arbors of DSGCs and that each dendritic spike initiates a somatic spike. We propose that dendritic spike failure, produced by local inhibitory inputs, might be a critical factor that enhances directional tuning of somatic spikes.
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Affiliation(s)
- Nicholas Oesch
- Neurological Sciences Institute, Oregon Health and Sciences University, Beaverton, Oregon 97006, USA
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26
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Poznanski RR. BIOPHYSICAL MECHANISMS AND ESSENTIAL TOPOGRAPHY OF DIRECTIONALLY SELECTIVE SUBUNITS IN RABBIT'S RETINA. J Integr Neurosci 2005; 4:341-61. [PMID: 16178062 DOI: 10.1142/s0219635205000860] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Accepted: 06/16/2005] [Indexed: 11/18/2022] Open
Abstract
We commemorate the 40th anniversary of the classical study undertaken by Barlow-Levick with a new challenge: to show how direction selectivity in the dendritic plexus of starburst amacrine cells is being computed. In the rabbit retina, although the cellular locus of direction selectivity is known to occur predominantly in the dendrites of starburst amacrine cells, the biophysical mechanism by which this takes place and its essential topography are yet to be specified with precision. A cotransmission model, involving a conjoint release of excitation/inhibition (i.e., a bisynaptic relay of endogenous ACh and GABA) from the distal varicosities of individual starburst amacrines, will be non-diphasic when the vesicular release of Ach and the non-vesicular, carrier-mediated release of GABA by transporters in the anterograde direction are preferentially suppressed by a negative feedback mechanism involving autoreceptors. Such biophysical mechanisms, including the asymmetric distribution of chloride cotransporters, explain somatofugal motion bias in starburst amacrine cells leading to autonomous functioning "subunits" that underlie the formation of directional selectivity. However, the functional independence of starburst amacrine cell "subunits" is partly a question of their network organization. The topography of directionally selective "subunits" resides in the plexus of crisscrossing dendrites of juxtaposed starburst amacrines, consisting of (i) serial synapses of three or more starburst amacrines and a ON-OFF directionally selective ganglion cell; (ii) a synaptic couplet between two starburst amacrines; and (iii) a conventional synapse between a starburst amacrine and a ON-OFF directionally selective ganglion cell. Cholinergic and GABAergic monosynaptic interactions between starburst amacrine cells, including glutamatergic interactions with cone bipolar cells, are involved in the primary circuit underlying directional selectivity. Furthermore, the secondary circuit underlying directional selectivity, consists of starburst amacrine cells and cone bipolar cells arranged in a "push-pull" configuration, interacting synaptically onto ON-OFF directionally selective ganglion cells.
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Affiliation(s)
- Roman R Poznanski
- Claremont Research Institute of Applied Mathematical Sciences, Claremont Graduate University, Claremont, CA 91711-3988, USA.
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27
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Fried SI, Münch TA, Werblin FS. Directional selectivity is formed at multiple levels by laterally offset inhibition in the rabbit retina. Neuron 2005; 46:117-27. [PMID: 15820698 DOI: 10.1016/j.neuron.2005.02.007] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 11/30/2004] [Accepted: 02/01/2005] [Indexed: 11/18/2022]
Abstract
The excitatory and inhibitory inputs to directionally selective (DS) ganglion cells are themselves directionally selective. Directionality is achieved because excitation is reduced during null-direction movement along a GABAergic pathway. Inhibition is reduced during preferred-direction movement along a pathway that includes cholinergic synapses. Both excitation and inhibition are made directional by laterally offset inhibitory signals similar to the spatial offset of the direct inhibitory input to the DS cell dendrites. Thus, spatially offset lateral inhibition generates directionality at three different levels in the DS circuitry. We also found that for stimuli falling within the dendritic field, cholinergic input is delivered to the OFF but not the ON dendrites. Cholinergic pathways from outside the dendritic field reach both ON and OFF dendrites, but both of these pathways are normally inactivated by GABAergic synapses.
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Affiliation(s)
- Shelley I Fried
- Vision Science, University of California at Berkeley, 145 LSA, Berkeley, California 94720, USA
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29
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Clifford CWG, Ibbotson MR. Fundamental mechanisms of visual motion detection: models, cells and functions. Prog Neurobiol 2002; 68:409-37. [PMID: 12576294 DOI: 10.1016/s0301-0082(02)00154-5] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Taking a comparative approach, data from a range of visual species are discussed in the context of ideas about mechanisms of motion detection. The cellular basis of motion detection in the vertebrate retina, sub-cortical structures and visual cortex is reviewed alongside that of the insect optic lobes. Special care is taken to relate concepts from theoretical models to the neural circuitry in biological systems. Motion detection involves spatiotemporal pre-filters, temporal delay filters and non-linear interactions. A number of different types of non-linear mechanism such as facilitation, inhibition and division have been proposed to underlie direction selectivity. The resulting direction-selective mechanisms can be combined to produce speed-tuned motion detectors. Motion detection is a dynamic process with adaptation as a fundamental property. The behavior of adaptive mechanisms in motion detection is discussed, focusing on the informational basis of motion adaptation, its phenomenology in human vision, and its cellular basis. The question of whether motion adaptation serves a function or is simply the result of neural fatigue is critically addressed.
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Affiliation(s)
- C W G Clifford
- Colour, Form and Motion Laboratory, Visual Perception Unit, School of Psychology, The University of Sydney, Sydney 2006, NSW, Australia.
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30
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Euler T, Detwiler PB, Denk W. Directionally selective calcium signals in dendrites of starburst amacrine cells. Nature 2002; 418:845-52. [PMID: 12192402 DOI: 10.1038/nature00931] [Citation(s) in RCA: 413] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The detection of image motion is fundamental to vision. In many species, unique classes of retinal ganglion cells selectively respond to visual stimuli that move in specific directions. It is not known which retinal cell first performs the neural computations that give rise to directional selectivity in the ganglion cell. A prominent candidate has been an interneuron called the 'starburst amacrine cell'. Using two-photon optical recordings of intracellular calcium concentration, here we find that individual dendritic branches of starburst cells act as independent computation modules. Dendritic calcium signals, but not somatic membrane voltage, are directionally selective for stimuli that move centrifugally from the cell soma. This demonstrates that direction selectivity is computed locally in dendritic branches at a stage before ganglion cells.
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Affiliation(s)
- Thomas Euler
- Max Planck Institute for Medical Research, Jahnstrasse 29, D-69120 Heidelberg, Germany.
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31
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Stasheff SF, Masland RH. Functional inhibition in direction-selective retinal ganglion cells: spatiotemporal extent and intralaminar interactions. J Neurophysiol 2002; 88:1026-39. [PMID: 12163551 DOI: 10.1152/jn.2002.88.2.1026] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We recorded from ON-OFF direction-selective ganglion cells (DS cells) in the rabbit retina to investigate in detail the inhibition that contributes to direction selectivity in these cells. Using paired stimuli moving sequentially across the cells' receptive fields in the preferred direction, we directly confirmed the prediction of that a wave of inhibition accompanies any moving excitatory stimulus on its null side, at a fixed spatial offset. Varying the interstimulus distance, stimulus size, luminance, and speed yielded a spatiotemporal map of the strength of inhibition within this region. This "null" inhibition was maximal at an intermediate distance behind a moving stimulus: 1/2 to 11/2 times the width of the receptive field. The strength of inhibition depended more on the distance behind the stimulus than on stimulus speed, and the inhibition often lasted 1-2 s. These spatial and temporal parameters appear to account for the known spatial frequency and velocity tuning of ON-OFF DS cells to drifting contrast gratings. Stimuli that elicit distinct ON and OFF responses to leading and trailing edges revealed that an excitatory response of either polarity could inhibit a subsequent response of either polarity. For example, an OFF response inhibited either an ON or OFF response of a subsequent stimulus. This inhibition apparently is conferred by a neural element or network spanning the ON and OFF sublayers of the inner plexiform layer, such as a multistratified amacrine cell. Trials using a stationary flashing spot as a probe demonstrated that the total amount of inhibition conferred on the DS cell was equivalent for stimuli moving in either the null or preferred direction. Apparently the cell does not act as a classic "integrate and fire" neuron, summing all inputs at the soma. Rather, computation of stimulus direction likely involves interactions between excitatory and inhibitory inputs in local regions of the dendrites.
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Affiliation(s)
- Steven F Stasheff
- Department of Neurology, Children's Hospital, Harvard Medical School, Boston 02115, USA.
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Vitanova L, Kupenova P, Haverkamp S, Popova E, Mitova L, Wässle H. Immunocytochemical and electrophysiological characterization of GABA receptors in the frog and turtle retina. Vision Res 2001; 41:691-704. [PMID: 11248259 DOI: 10.1016/s0042-6989(00)00294-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The expression of GABA receptors (GABARs) was studied in frog and turtle retinae. Using immunocytochemical methods, GABA(A)Rs and GABA(C)Rs were preferentially localized to the inner plexiform layer (IPL). Label in the IPL was punctate indicating a synaptic clustering of GABARs. Distinct, but weaker label was also present in the outer plexiform layer. GABA(A)R and GABA(C)R mediated effects were studied by recording electroretinograms (ERGs) and by the application of specific antagonists. Bicuculline, the GABA(A)R antagonist, produced a significant increase of the ERG. Picrotoxin, when co-applied with saturating doses of bicuculline, caused a further increase of the ERG due to blocking of GABA(C)Rs. The putative GABA(C)R antagonist Imidazole-4-acidic acid (I4AA) failed to antagonize GABA(C)R mediated inhibition and, in contrast, appeared rather as an agonist of GABARs.
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Affiliation(s)
- L Vitanova
- Department of Physiology, Medical University, Sofia, Bulgaria
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33
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Borg-Graham LJ. The computation of directional selectivity in the retina occurs presynaptic to the ganglion cell. Nat Neurosci 2001; 4:176-83. [PMID: 11175879 DOI: 10.1038/84007] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Directional selectivity is a response that is greater for a visual stimulus moving in one (PREF) direction than for the opposite (NULL) direction, and its computation in the vertebrate retina is a classical issue in functional neurophysiology. To date, most quantitative experimental studies have relied on extracellular responses for identifying properties of the directionally selective circuit. Here I describe an intracellular analysis using whole-cell patch recordings of the synaptic events underlying the spike response in directionally selective ganglion cells of the turtle retina. These quantitative measurements allowed me to distinguish among various explicit classes of circuit models that can, in principle, account for ganglion cell directional selectivity. I found that ganglion cell directional selectivity is due to an excitatory input that itself is directionally selective, and that the crucial shunting inhibition implicated in this computation must act on cells presynaptic to the ganglion cell.
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Affiliation(s)
- L J Borg-Graham
- Unité de Neurosciences Intégrative et Computationnelles, UPR CNRS 2191-INAF CNRS, 91198 Gif-sur-Yvette, France.
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34
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Brown SP, Masland RH. Spatial scale and cellular substrate of contrast adaptation by retinal ganglion cells. Nat Neurosci 2001; 4:44-51. [PMID: 11135644 DOI: 10.1038/82888] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Human visual perception and many visual system neurons adapt to the luminance and contrast of the stimulus. Here we describe a form of contrast adaptation that occurs in the retina. This adaptation had a local scale smaller than the dendritic or receptive fields of single ganglion cells and was insensitive to pharmacological manipulation of amacrine cell function. These results implicate the bipolar cell pathway as a site of contrast adaptation. The time required for contrast adaptation varied with stimulus size, ranging from approximately 100 ms for the smallest stimuli, to seconds for stimuli the size of the receptive field. The differing scales and time courses of these effects suggest that multiple types of contrast adaptation are used in viewing natural scenes.
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Affiliation(s)
- S P Brown
- Program in Neuroscience, Goldenson 228, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abstract
The development of cholinergic cells in the rat retina has been examined with immunocytochemistry by using antisera against choline acetyltransferase (ChAT). ChAT-immunoreactive (IR) cells were first detected at embryonic day 17 (E17) in the transitional zone between the neuroblastic layer (NBL) and ganglion cell layer (GCL). At E20, ChAT-IR cells are located exclusively in the GCL. At postnatal day 0 (P0), ChAT immunoreactivity appeared for the first time in cells at the distal margin of the NBL. Two prominent bands of labeled processes were first visible at P3, and by P15, these two bands resembled those of the adult retina. In addition, ChAT immunoreactivity appeared transiently in horizontal cells from P5 to P10. The number of ChAT-IR cells increased steadily up to P15. This resulted in a 93.8-fold increase between E17 and P15 (680-63,800 cells). However, after P15, the number declined by 19% from 63,800 cells at P15 to 51,800 in the adult. At all ages, the spatial density of each ChAT-IR cell population in the central retina was higher than in the periphery. In both central and peripheral regions, the peak density of ChAT-IR cells in the GCL was attained at E20. However, in the INL, the peak densities occurred at P3 in the central region and at P5 in the peripheral region. Up to P15, the soma diameter of ChAT-IR cells in the INL and GCL in each region increased continuously, reaching peak values at P15. Our results demonstrate that ChAT immunoreactivity is expressed in early developmental stages in the rat retina, as in other mammals, and that acetylcholine released from ChAT-IR cells may have neurotrophic functions in retinal maturation.
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Affiliation(s)
- I B Kim
- Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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Nguyen LT, Grzywacz NM. Colocalization of choline acetyltransferase and gamma-aminobutyric acid in the developing and adult turtle retinas. J Comp Neurol 2000; 420:527-38. [PMID: 10805925 DOI: 10.1002/(sici)1096-9861(20000515)420:4<527::aid-cne9>3.0.co;2-i] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Acetylcholine and gamma -aminobutyric acid (GABA) are putative neurotransmitters in the adult vertebrate retina. In this study, cells that coexpress choline acetyltransferase (ChAT) and GABA or glutamic acid decarboxylase (GAD) were investigated in turtle retinas from stage 14 (S14) to adulthood by using a double-labeling immunofluorescence technique. ChAT immunoreactivity was observed at S15 and included not only the presumptive starburst cholinergic amacrine cells but also a population in the ganglion cell layer (GCL) that expressed ChAT transiently during the embryonic stages (see the accompanying paper: Nguyen et al. [2000] J. Comp. Neurol. 420:512-526).
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Affiliation(s)
- L T Nguyen
- The Smith-Kettlewell Eye Research Institute, San Francisco, California 94115, USA
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37
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Abstract
Visual field loss in glaucoma is due to death of retinal ganglion cells. Reducing or slowing down the loss of ganglion cells in glaucoma, a concept known as neuroprotection, would appear to be the only way forward. This does not imply that treatment of risk factors, such as elevated intraocular pressure, must not be continuously implemented. In this paper we point out that very little is known about the mechanisms of ganglion cell death in glaucoma and that data derived from studies on the "ideal animal model for glaucoma" must not be overemphasized. We also propose that the death processes of neurones in various diseases are fundamentally the same but vary in cause. Experimental data show that the death rate of neuronal populations is dependent on the impact of the insult and that neuroprotectants are more likely to benefit a patient in diseases in which the neurones die slowly, as in glaucoma, than in a disease in which the death of a set of neurones is rapid. We conclude that if a putative neuroprotectant can be administered in such a way that it reaches the retina in appropriate amounts and has insignificant side effects, it is likely to attenuate ganglion cell death and thus benefit the glaucoma patient.
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Affiliation(s)
- N N Osborne
- Nuffield Laboratory of Ophthalmology, Oxford University, UK
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38
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Affiliation(s)
- S C Mangel
- Department of Neurobiology, University of Alabama School of Medicine, Birmingham, AL 35294, USA
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39
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Akopian A, Gabriel R, Witkovsky P. Calcium released from intracellular stores inhibits GABAA-mediated currents in ganglion cells of the turtle retina. J Neurophysiol 1998; 80:1105-15. [PMID: 9744925 DOI: 10.1152/jn.1998.80.3.1105] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We studied spiking neurons isolated from turtle retina by the whole cell version of the patch clamp. The studied cells had perikaryal diameters > 15 microns and fired multiple spikes in response to depolarizing current steps, indicating they were ganglion cells. In symmetrical [Cl-], currents elicited by puffs of 100 microM gamma-aminobutyric acid (GABA) were inward at a holding potential of -80 mV. All of the GABA-evoked current was blocked by SR95331 (20 microM), indicating that it was mediated by a GABAA receptor. The GABA-evoked currents were unaltered by eliciting a transmembrane calcium current either just before or during the response to GABA. On the other hand caffeine (10 mM), which induces Ca2+ release from intracellular stores, inhibited the GABA-evoked current on average by 30%. The caffeine effect was blocked by introducing the calcium buffer bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) into the cell but was unaffected by replacing [Ca2+]o with equimolar cobalt. Thapsigargin (10 microM), an inhibitor of intracellular calcium pumps, and ryanodine (20 microM), which depletes intracellular calcium stores, both markedly reduced a caffeine-induced inhibition of the GABA-evoked current. Another activator of intracellular calcium release, inositol trisphosphate (IP3; 50 microM), also progressively reduced the GABA-induced current when introduced into the cell. Dibutyryl adenosine 3'5'-cyclic monophosphate (cAMP; 0.5 mM), a membrane-permeable analogue of cAMP, did not reduce GABA-evoked currents, suggesting that cAMP-dependent kinases are not involved in suppressing GABAA currents, whereas calmidazolium (30 microM) and cyclosporin A (20 microM), which inhibit Ca/calmodulin-dependent phosphatases, did reduce the caffeine-induced inhibition of the GABA-evoked current. Alkaline phosphatase (150 micrograms/ml) and calcineurin (300 micrograms/ml) had a similar action to caffeine or IP3. Antibodies directed against the ryanodine receptor or the IP3 receptor reacted with the great majority of neurons in the ganglion cell layer. We found that these two antibodies colocalized in large ganglion cells. In summary, intracellular calcium plays a role in reducing the currents elicited by GABA, acting through GABAA receptors. The modulatory action of calcium on GABA responses appears to work through one or more Ca-dependent phosphatases.
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Affiliation(s)
- A Akopian
- Department of Ophthalmology, New York University School of Medicine, New York 10016, USA
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40
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Abstract
Rod bipolar (RB) cells of mammalian retinae receive synapses from different gamma-aminobutyric acid (GABAergic) amacrine cells in the inner plexiform layer (IPL). We addressed the question whether RB cells of the rabbit and of the rat retina express different types of GABA receptors at these synapses. RB cells were immunolabeled in vertical sections of rat retinae with an antibody against protein kinase C (PKC). The sections were double-labeled for the alpha 1, alpha 2, alpha 3, or gamma 2 subunits of the GABAA receptor. Punctate immunofluorescence, which represents synaptic localization, was found for all four subunits. Many of the alpha 1-, alpha 3-, or gamma 2-immunoreactive puncta coincided with the axon terminals of the PKC-immunolabeled RB cells. Sections and wholemounts of rabbit retinae were also double labeled for PKC and the rho subunits of the GABAC receptor. Rabbit RB cells were decorated by many rho-immunoreactive puncta, which were shown by electron microscopy to represent synaptic localization. Previous work from our laboratory has shown that the alpha 1, alpha 2, alpha 3, and rho subunits are not found within the same synapse but are expressed at different synaptic sites. Taken together, these results suggest that RB cells of mammalian retinae express at least three different types of GABA receptors at synaptic sites in the IPL: GABAC receptors, GABAA receptors containing the alpha 1 subunit, and GABAA receptors containing the alpha 3 subunit.
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Affiliation(s)
- E L Fletcher
- Max-Planck-Institut für Hirnforschung, Frankfurt, Germany
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