Rabbit Retina Research Articles

Analysis of melanopsin gene expression in the rabbit retina at different ages.

Melanopsin is the photopigment of intrinsically photosensitive retinal ganglion cells that mediate non-visual responses to light. The aim of this study was to describe and analyze melanopsin gene expression in the rabbit retina at different ages and compare its expression with the prototypic gene of retinal ganglion cells (Thy-1 gene). Expression levels of OPN4, Thy-1, and GADPH genes were measured by real-time PCR at 3, 4, 8, 11, 12, 17, 19, 20, 23, 27, 32, and 47 postnatal days. We also regrouped the days before and after day 12 of life (pre-photic and post-photic stage, respectively). Average expression of the OPN4 gene between days was similar (P = 0.713), but was statistically different in the Thy-1 gene (P = 0.004). Also, no significant differences were found in OPN4 gene expression pre-photic and post-photic stage (P = 0.629); however, Thy-1 expression was higher in the pre-photic stage, almost double, than in the post-photic stage, with significant differences (P = 0.001). This is the first report describing OPN4 gene expression in the rabbit retina at different ages. We demonstrated that the OPN4 gene is constantly expressed at all early stages, even before the onset of photoentrainment by the pups and that Thy-1 and OPN4 gene expressions are out of phase.

Potential hazards of glyphosate on rabbit retina

Background/aim Retinal degeneration is a leading cause of vision loss. Exposure to pesticides is a high risk factor of retinal degeneration. The aim of the work is to investigate the molecular structural changes of retina associated with the topical application of glyphosate (GLP), an organophosphorus compound pesticide.Materials and methods Twenty rabbits were randomly categorized into four groups. Group I served as control (n=5, 10 eye balls) and the other three groups (each composed of five rabbits) received topical instillation of 100 μl twice a day of GLP in three concentrations of 0.12, 0.97, and 7.8 mg/kg, respectively. After 1 week, eyes were enucleated and retinae were removed and prepared for analysis by infrared spectroscopy (Fourier-transform infrared spectroscopy).Results The regions of NH–OH spectra indicated a significant decrease (P<0.05) in wavenumber and restriction of two components related to strO–H and OHasym band after application of GLP. The protein secondary structure components in terms of β sheets, alpha helices and β turns were changed in groups III and IV. Also the fingerprint regions indicate changes in the surrounding environment after all doses of GLP.Conclusion Certain retinal structure modifications may lead to the degeneration of retina after topical exposure to GLP in rabbits. So this herbicide should be handled with caution. National governments must introduce a GLP reduction program because of its damage effect on retina function.

Ameliorative Effect of Grape Seed Proanthocyanidin Extract on Argon-Laser Induced Retinal Damage

Photocoagulation is routinely used as a major treatment method for many retinal disorders. The present study was conducted to investigate the protective effect of Grape seed extract (GSE) on reactive oxygen species produced during argon laser photocoagulation and also to explore the benefit of retinal photocoagulation over two session's argon laser compared to single session. Forty two pigmented rabbits weighted 2–2.5 Kg were used in this study. The animals were classified into three groups. The left eye for each animal was photocoagulated with 200 mW, 400 mW and 400 mw fractionated dose (FD) argon laser with and without GSE supplementation respectively. After 24 hours the retina was separated carefully, malondialdehyde level (MDA), total antioxidant capacity (TAC) and Fourier transform infrared spectroscopy (FT-IR) for retinal tissue were detected. FT-IR findings showed a positive result for GSE supplementation in reducing laser effects on the retinal tissue. Also, GSE supplementation improved the level of TAC in rabbit's retina exposed to argon laser with a concurrent decrease in MDA level. In conclusion, GSE has an extremely beneficial role in overcoming the resultant adverse biological effects of argon laser photocoagulation on retinal tissues due to its potent antioxidant properties. Results also revealed that retinal photocoagulation over two sessions was more protective for retinal tissue than single session argon laser.

Expression of Nicotinic Acetylcholine Receptor α4 and β2 Subunits on Direction-Selective Retinal Ganglion Cells in the Rabbit

The direction selectivity of the retina is a distinct mechanism that is critical function of eyes for survival. The direction-selective retinal ganglion cells (DS RGCs) strongly respond to a preferred direction, but rarely respond to opposite direction or null directional visual stimuli. The DS RGCs are sensitive to acetylcholine, which is secreted from starburst amacrine cells (SACs) to the DS RGCs. Here, we investigated the existence and distribution of the nicotinic acetylcholine receptor (nAChR) α4 and β2 subunits on the dendritic arbors of the DS RGCs in adult rabbit retina using immunocytochemistry. The DS RGCs were injected with Lucifer yellow to identify their dendritic morphology. The double-labeled images of dendrites and nAChR subunits were visualized for reconstruction using high-resolution confocal microscopy. Although our results revealed that the distributional pattern of the nAChR subunits on the dendritic arbors of the DS RGCs was not asymmetric in the adult rabbit retina, the distribution of nAChR α4 and β2 subunits and molecular profiles of cholinergic inputs to DS RGCs in adult rabbit retina provide anatomical evidence for direction selectivity.

Long-Term Protection of Genetically Ablated Rabbit Retinal Degeneration by Sustained Transscleral Unoprostone Delivery.

To evaluate the long-term protective effects of transscleral unoprostone (UNO) against retinal degeneration in transgenic (Tg) rabbits (Pro347Leu rhodopsin mutation). The UNO release devices (URDs) were implanted into the sclerae of Tg rabbits and ERG, optical coherence tomography (OCT), and ophthalmic examinations were conducted for 40 weeks. Unoprostone metabolites in retina, choroid/RPE, aqueous humor, and plasma from wild-type (Wt) rabbits were measured using liquid chromatography-tandem mass spectrometry. In situ hybridization and immunohistochemistry evaluated the retinal distribution of big potassium (BK) channels, and RT-PCR evaluated the expressions of BK channels and m-opsin at 1 week after URD treatment. The URD released UNO at a rate of 10.2 ±1.0 μg/d, and the release rate and amount of UNO decreased during 32 weeks. Higher ERG amplitudes were observed in the URD-treated Tg rabbits compared with the placebo-URD, or nontreated controls. At 24 weeks after implantation into the URD-treated Tg rabbits, OCT images showed preservation of retinal thickness, and histologic examinations (44 weeks) showed greater thickness of outer nuclear layers. Unoprostone was detected in the retina, choroid, and plasma of Wt rabbits. Retina/plasma ratio of UNO levels were 38.0 vs. 0.68 ng UNO*hour/mL in the URD-treated group versus control (topical UNO), respectively. Big potassium channels were observed in cone, cone ON-bipolar, and rod bipolar cells. Reverse-transcriptase PCR demonstrated BK channels and m-opsins increased in URD-treated eyes. In Tg rabbits, URD use slowed the decline of retinal function for more than 32 weeks, and therefore provides a promising tool for long-term treatment of RP.

Photoreceptor degeneration by intravitreal injection of N-methyl-N-nitrosourea (MNU) in rabbits: a pilot study.

Pilot study on the attempt to induce selective photoreceptor degeneration in the rabbit eye by intravitreal injection of MNU, facing the difficulties of the evaluation of retinal degeneration by different in-vivo and in-vitro methods in such a large eye animal model. Eight pigmented Chinchilla Bastard rabbits were injected intravitreally with MNU (1× 1mg/kg body weight (BW), 1× 2mg/kg BW, 3× 3mg/kg BW, 1× 4mg/kg BW, 1× 6mg/kg BW, and 1× DMSO + PBS as control). One, 2, and 3weeks after injection, the effects on the rabbit retina were examined in vivo using clinical observation (macroscopic images, funduscopy, weighing of the animals), measurement of intraocular pressure (IOP), full-field Electroretinography (ffERG), and spectral-domain Optical Coherence Tomography (sd-OCT). After3weeks follow-up, blood samples were taken to evaluate the general health status of the animals, and immunohistochemistry (IH) was performed on sections obtained from six different regions throughout the whole retina to evaluate MNU effects in more detail. It was difficult to observe the effects of MNU on retinal structure by OCT in vivo. Only the temporal quadrant of the retina could be visualized. Therefore, it was indispensible to evaluate the effects of MNU on the retina in vitro by examining six areas of the retina using immunohistochemistry. Furthermore, immunohistochemistry plays a decisive role to evaluate the effects on retinal cells other than photoreceptors while in H&E staining, namely the cell count of the ONL can be observed. The results obtained in vivo and in vitro in this study mainly follow the results of a previous study in mice. The low doses of MNU (1, 2 mg/kg BW) had no effects on retinal function and morphology, while high doses (4, 6 mg/kg BW) led to retinal changes in combination with significant side-effects (e.g., cataractous changes). Injection of 3 mg/kg BW MNU induced selective photoreceptor degeneration. However, the degree of degeneration varied between different parts of the same retina and between retinae of different animals. In two of three animals, a complete loss of ERG potentials was observed. Negative effects on the contralateral eye or on general welfare of the animal were never observed. In rabbits, the intravitreal injection of 3 mg/kg BW MNU leads to selective but inhomogeneous photoreceptor degeneration.

Screening of optimal ultrasound parameters after intravitreal injection of microbubble in normal rabbit eyes

Background Ultrasound microbubbles play important effects on delivery of drug or gene, which can significantly improve the transfection efficiency of drug or gene after ultrasonic irradiation.However, different ultrasonic irradiation parameters have different biological effects on different cells. Objectives This study was to investigate the effects of ultrasound microbubble on normal rabbit retina in different ultrasound intensities and irradiation time and provide the experimental basis for the treating study of fundus diseases with ultrasound microbubble. Methods Eighteen clean New Zealand albino rabbits were randomized into blank control group, simple ultrasound radiation group, simple intraocular injection group and intraocular injection+ low, moderate and high intensity ultrasound groups.No intervention was performed in the blank control group.Only 2.0 W/cm2 ultrasound radiated for 60 seconds or 0.1 ml microbubbles were injected in vitreous cavity respectively in the simple ultrasound radiation group or simple intraocular injection group.The ultrasound with the intensity of 0.5, 1.0 and 2.0 W/cm2 radiated the eyes with intraocular injection of microbubbles for 60 seconds in the intraocular injection+ low, moderate and high intensity ultrasound groups, respectively.The photography of ocular anterior segment, direct ophthalmoscopy and color fundus photography were performed before operation, immediately after operation and 1 day, 7 days after operation.The retinas were isolated in the seventh day and hematoxylin & eosin staining was carried out for the evaluation of retinal morphology.The ultrastructure of the retinas was examined by transmission electron microscope.This study protocol was approved by Ethic Committee of Experimental Animals Use and Care in Shenzhen Eye Hospital. Results There were not abnomal findings by slit lamp microscope and ophthalmoscope in the eyes of various groups at different time points.In the intraocular injection+ moderate and high intensity ultrasound groups, the loosening of retinal layers, disorder of photoreceptors, thinning of inner and outer nuclear layers as well as the decrease of retinal ganglion cells (RGCs) were exhibited under the optical microscope, and mitochondrial swelling of photoreceptors, noneven of chromatin in nucleus and losing of RGCs were found under the transmission electron microscope.However, the retinal morphology and ultrastructure were normal in the blank control group, simple ultrasound radiation group, simple intraocular injection group and intraocular injection+ low intensity ultrasound group. Conclusions Ultrasound irradiation in the intensity 0.5 W/cm2 for 60 seconds is safe and suitable for retina in the eyes with intraocular injection of microbubble.This result provides an experimental basis for the management of fundus diseases by ultrasound microbubble. Key words: Retina; Ultrasonics; Microbubbles; Sonication; Intravitreal injection; Ultrasound parameter; Rabbits

Complexity of gap junctions between horizontal cells of the carp retina

In the vertebrate retina, horizontal cells (HCs) reveal homologous coupling by gap junctions (gj), which are thought to consist of different connexins (Cx). However, recent studies in mouse, rabbit and zebrafish retina indicate that individual HCs express more than one connexin. To provide further insights into the composition of gj connecting HCs and to determine whether HCs express multiple connexins, we examined the molecular identity and distribution of gj between HCs of the carp retina.We have cloned four carp connexins designated Cx49.5, Cx55.5, Cx52.6 and Cx53.8 with a close relationship to connexins previously reported in HCs of mouse, rabbit and zebrafish, respectively. Using in situ hybridization, Cx49.5 expression was detected in different subpopulations of retinal neurons including HCs, whereas the Cx52.6 transcript was localized exclusively in HCs. Using specific antibodies, Cx55.5 and Cx53.8 were detected on dendrites of all four HC subtypes and axon terminals. Immunoelectron microscopy confirmed the presence of Cx55.5 and Cx53.8 in gap junctions between these processes and Cx55.5 was additionally observed in HC dendrites invaginating cone pedicles, suggesting its participation in the modulation of photoreceptor output in the carp retina. Furthermore, using single-cell RT–PCR, all four connexins were detected in different subtypes of HCs, suggesting overlapping expression patterns. Thus, the composition of gj mediating homologous coupling between subtypes of carp HCs appears to be more complex than expected. Moreover, BLAST searches of the preliminary carp genome, using novel sequences as query, suggest that most of the analyzed connexin genes are duplicated in carp.

Histopathological Changes of Inner Retina, Optic Disc, and Optic Nerve in Rabbit with Advanced Retinitis Pigmentosa

ABSTRACTWe observed the histopathological changes of retinal ganglion cells (RGCs), optic disc, and optic nerve in rabbit with advanced retinitis pigmentosa (RP). Wild-type (WT) and rhodopsin transgenic (Tg) of RP rabbits were used at age 24 months. Light and electron microscopy were used to observe the retina, optic disc, and optic nerve. RGCs were also confirmed by immunofluorescent staining with a TUJ-1 monoclonal antibody. In addition to the rod and cone degeneration, we observed the astrocyte infiltration of the optic disc due to the damage of small RGCs and nerve fibres and atrophy of small optic nerve fibres. They subsequently lead to the optic disc excavation and atrophy of the optic nerve. Consequently, our histopathological study clarified that not only the outer retina but also the inner retina, the optic disc, and the optic nerve were also affected in the late stages of RP rabbit.

Membrane-associated guanylate kinase scaffolds organize a horizontal cell synaptic complex restricted to invaginating contacts with photoreceptors.

Synaptic processes and plasticity of synapses are mediated by large suites of proteins. In most cases, many of these proteins are tethered together by synaptic scaffold proteins. Scaffold proteins have a large number and typically a variety of protein interaction domains that allow many different proteins to be assembled into functional complexes. Because each scaffold protein has a different set of protein interaction domains and a unique set of interacting partners, the presence of synaptic scaffolds can provide insight into the molecular mechanisms that regulate synaptic processes. In studies of rabbit retina, we found SAP102 and Chapsyn110 selectively localized in the tips of B-type horizontal cell processes, where they contact cone and rod photoreceptors. We further identified some known SAP102 binding partners, kainate receptor GluR6/7 and inward rectifier potassium channel Kir2.1, closely associated with SAP102 in photoreceptor invaginations. The kainate receptor occupies a position distinct from that of the majority of AMPA receptors that dominate the horizontal cell postsynaptic response. GluR6/7 and Kir2.1 presumably are involved in synaptic processes that govern cell-to-cell communication and could both contribute in different ways to synaptic currents that mediate feedback signaling. Notably, we failed to find evidence for the presence of Cx57 or Cx59 that might be involved in ephaptic feedback signaling in this complex. The presence of SAP102 and its binding partners in both cone and rod invaginating synapses suggests that whatever mechanism is supported by this protein complex is present in both types of photoreceptors. J. Comp. Neurol. 525:850-867, 2017. © 2016 Wiley Periodicals, Inc.

Computational neuroscience: Species-specific motion detectors.

A range of neuronal mechanisms can enable animals to detect the direction of visual motion. Computational models now indicate that a factor as simple as eye size might explain some of this diversity. See Article p.105 The starburst amacrine cell (SAC) dendrites of the retina play an essential role in the computation of direction selectivity in the detection of moving visual stimuli. Past studies of SAC anatomy have mostly involved the rabbit retina. Now Kevin Briggman and colleagues present a large-scale reconstruction of the mouse retina at single-synapse level, which reveals a striking asymmetry in the distribution of inhibitory and excitatory input synapses onto SAC dendrites. Using computer modelling and further physiological imaging, the authors demonstrate that the mouse-specific retinal circuitry is adapted to its smaller eye size, compared to the rabbit. Without this adaptation, mice would be blind to slowly moving objects.

Histological and Immunohistochemical Retinal Changes Following the Intravitreal Injection of Aflibercept, Bevacizumab and Ranibizumab in Newborn Rabbits

ABSTRACTPurpose: To analyze the retinal effects of the intravitreally administered vascular endothelial growth factor (VEGF) inhibitors (aflibercept, bevacizumab and ranibizumab) in newborn rabbits.Methods: Right eyes of 28 two-week-old New Zealand albino rabbits comprised the study population. Four eyes received intravitreal injection of 0.025cc balanced salt solution (BSS) (group I, control group); six 0.25 mg ranibizumab (group II), six 0.3125 mg bevacizumab (group III), six 0.625 mg bevacizumab (group IV), and six 1 mg aflibercept (group V) intravitreally. Blood samples were obtained to evaluate serum VEGF levels. Retinal tissues were examined by light microscopy and immunohistochemical examination (TUNEL and caspase-3 staining) to evaluate the level of apoptosis at the end of the third week.Results: Light microscopic evaluation did not show any retinal abnormality in all study and control eyes. Positive TUNEL staining was present in 16.75 ± 1.25%, 23.6 ± 1.36%, 33.1 ± 5.03%, 49.3 ± 9.3%, and 32.33 ± 8.06% of the eyes recruited in groups I, II, III, IV, and V, respectively. Mean percentage of apoptotic cell counts detected by caspase-3 staining was as follows: 6.75 ± 2.06% in Group I, 12.6 ± 13.44% in Group II, 15.5 ± 1.37% in Group III, 24.0 ± 2.7% in Group IV, and 17.33 ± 1.96% in Group V. TUNEL and caspase-3 staining ratio was found to be statistically higher in all anti-VEGF drug groups compared to the controls (TUNEL stain; p = 0.01, p = 0.01, p = 0.01, p = 0.01; caspase-3 stain; p = 0.024, p = 0.009, p = 0.01, p = 0.01, respectively). Serum VEGF levels were 82.16 ± 1.72 pg/mL, 54.53 ± 12.69 pg/mL, 33.09 ± 17.26 pg/mL, 39.66 ± 5.77 pg/mL, and 36.90 ± 28.14 pg/mL for the control groups II, III, IV, and V, respectively. Serum VEGF concentrations were found to be statistically lower in the anti-VEGF groups compared to the control eyes (p = 0.011, p = 0.011, p = 0.011, p = 0.014, respectively).Conclusion: This study demonstrates that apoptosis was induced in the retina of newborn rabbits by intravitreal administration of anti-VEGF agents together with reduction in serum VEGF levels. Among the three anti-VEGF agents, ranibizumab caused the least apoptotic activity in the retina and reduction in serum VEGF levels. In light of our study, we believe that intravitreal anti-VEGF agents should be used with caution as a first line treatment for the treatment of retinopathy of prematurity.

Proteomic analysis of retinal proteins in rabbits following intravitreal PBS injection: analysis with tandem mass tag labeling coupled with LC-MS/MS.

Intravitreal (IVT) injection has become one of the most commonly performed ophthalmologic procedures. We investigated the changes in retinal function and proteomics in rabbits receiving IVT injection of PBS to evaluate the safety of IVT injection. Twenty Chinchilla rabbits were subjected to IVT injection of 50 µL PBS in the right eyes. On days 0, 4, 7 and day 14, the retinas of the rabbits were isolated after routine ophthalmic and electroretinogram examinations. The protein expressions in the retinas were quantified using tandem mass tag (TMT)-labeling coupled with LC-MS/MS, and bioinformatic analysis of the differentially expressed proteins (DEPs) was performed based on KEGG database to identify significantly enriched pathways. Functional network of the significant DEPs was analyzed using STRING. No noticeable fundus or functional changes occurred in the rabbit eyes following IVT injection of PBS. A total of 6042 retinal proteins were identified in the retina following the injection, among which 49 proteins (0.81%) exhibited over 5.0-fold up-regulation or over 80% down- regulation relative to the control. Most of the distinctly up-regulated or down-regulated proteins were associated with the cytoskeleton. Significantly enriched pathways involved focal adhesion, tight junction, riboflavin metabolism, extracellular matrix-receptor interaction and regulation of actin cytoskeleton. Functional network analysis showed that ACTC1 and ISG15 played central roles in the protein interaction networks. IVT PBS injection in rabbits causes alterations in proteins associated with cell adhesion, morphology, migration, differentiation, signal transduction and riboflavin metabolism, but the alterations of the retinal proteins appear not sufficient to cause observable pathology of the retina.

The Preventive Effects of Adrenalectomy in Metha- nol Intoxication on Photoreceptors in Rabbit Retina (Oryctolagus cuniculus): Ultrastructural Study

The Preventive Effects of Adrenalectomy in Metha- nol Intoxication on Photoreceptors in Rabbit Retina (Oryctolagus cuniculus): Ultrastructural Study

Сравнительная характеристика влияния двухнедельной тампонады жидких перфторуглеродов и «легкого» силиконового масла на биоэлектрическую функциональную активность сетчатки глаза кролика

Сравнительная характеристика влияния двухнедельной тампонады жидких перфторуглеродов и «легкого» силиконового масла на биоэлектрическую функциональную активность сетчатки глаза кролика

The effects on rabbit corneas and retinas after single intravitreal injection of voriconazole at different doses

Objective To observe the effects on rabbit corneas and retinas after single intravitreal injection of voriconazole at different doses. Methods According to the randomization table, 25 healthy rabbits were randomly divided into control group, and voriconazole 50, 100, 200, and 400 μg groups. Therefore, there were 5 rabbits in each group. The eyes of control group received intravitreal injection of 0.1 ml balanced saline solution, and those treatment groups received 0.1 ml voriconazole injection of corresponding dose. Before the injection and 1, 7, and 14 days after the injection, endothelial cell counts and corneal thicknesses were measured; full-field electroretinogram were performed and b-wave amplitudes in maximal combined reaction (Max-R) were recorded. On 14 days after the injection, histologic structures were observed by light microscope and transmission electron microscope. Results There was no significant difference in endothelial cell counts (F=0.320, 0.291, 0.467, 0.649) and corneal thicknesses (F=0.214, 0.284, 0.360, 0.225) with those of control group at any time points (P>0.05). Before and 1 day after the injection, b-wave amplitudes of each voriconazole group had no significant difference compared with those of control group (F=0.220, 0.106; P>0.05). On 7 days after the injection, b-wave amplitudes decreased significantly at doses of 200 μg and 400 μg (P 0.05). However, the amplitude of the 400 μg group decreased continuously and there was still significant difference (P<0.05). Light microscopy did not reveal any corneal abnormality in both control group and voriconazole groups. The retinas were normal except that of the 400 μg group, which had a thinner and degenerated inner nuclear layer and disordered photoreceptor layer. Under transmission electron microscope, there were no ultrastructure damages of corneas in both control group and voriconazole groups, either. The rabbit retinas of the 50 μg and 200 μg group have normal inner nuclear layer and photoreceptor layer, but degrees of changes in both layers were observed in the eyes of 200 μg and 400 μg group. Conclusions There is no obvious effects on rabbit corneas and retinas after single intravitreal injection of voriconazole at he dose less than or equal 100 μg. There are no obvious effects on rabbit corneas at the dose of 200 μg and 400 μg, while there are damages to the retinas in both functions and histological structures. Key words: Retina/drug effects; Cornea/drug effects; Triazoles/administration & dosage; Animal experimentation

Safety of intravitreal quinupristin/dalfopristin in an animal model.

To determine whether different intravitreal doses of quinupristin/dalfopristin lead to electroretinographic or histological changes in the rabbit retina over one month period after injection. Eighteen New Zealand white rabbits were divided into three treatment groups (groups 1 to 3) and different intravitreal doses of quinupristin/dalfopristin were tested in each group. The right eye was injected with the drug and the left eye received intravitreal injection of 5% dextrose water and served as control eye. The doses delivered to each group were 0.1 mg/0.1 mL, 1 mg/0.1 mL and 10 mg/0.1 mL. Simultaneous, bilateral, dark-adapted electroretinography and clinical images of both eyes were obtained in all groups before injection (baseline) and after 7, 14, 21 and 28d, followed by enucleation for histological examination. Subjects in the group 1 showed no signs of toxicity in the electroretinogram when compared with groups 2 and 3 (Kruskall-Wallis test, P=0.000). By day 7, no electrical response to light stimuli was recorded in the treated eyes in groups 2 and 3, consistent with severe damage due to retinal toxicity. Light microscopy revealed no significant histopathological changes in the group 1, while rabbits in groups 2 and 3 had signs of granulomatous inflammation in most cases. Intravitreal 0.1 mg/0.1 mL doses of quinupristin/dalfopristin do not lead to electroretinographic or histological signs of retinal toxicity compared with 1 mg/0.1 mL and 10 mg/0.1 mL in this rabbit model.

Synaptic Mechanisms Generating Orientation Selectivity in the ON Pathway of the Rabbit Retina.

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.

Event-Based Computation of Motion Flow on a Neuromorphic Analog Neural Platform.

Estimating the speed and direction of moving objects is a crucial component of agents behaving in a dynamic world. Biological organisms perform this task by means of the neural connections originating from their retinal ganglion cells. In artificial systems the optic flow is usually extracted by comparing activity of two or more frames captured with a vision sensor. Designing artificial motion flow detectors which are as fast, robust, and efficient as the ones found in biological systems is however a challenging task. Inspired by the architecture proposed by Barlow and Levick in 1965 to explain the spiking activity of the direction-selective ganglion cells in the rabbit's retina, we introduce an architecture for robust optical flow extraction with an analog neuromorphic multi-chip system. The task is performed by a feed-forward network of analog integrate-and-fire neurons whose inputs are provided by contrast-sensitive photoreceptors. Computation is supported by the precise time of spike emission, and the extraction of the optical flow is based on time lag in the activation of nearby retinal neurons. Mimicking ganglion cells our neuromorphic detectors encode the amplitude and the direction of the apparent visual motion in their output spiking pattern. Hereby we describe the architectural aspects, discuss its latency, scalability, and robustness properties and demonstrate that a network of mismatched delicate analog elements can reliably extract the optical flow from a simple visual scene. This work shows how precise time of spike emission used as a computational basis, biological inspiration, and neuromorphic systems can be used together for solving specific tasks.

Влияние тридцатидневной тампонады перфторорганическими соединениями на биоэлектрическую функциональную активность и структуру сетчатки глаза кролика

Влияние тридцатидневной тампонады перфторорганическими соединениями на биоэлектрическую функциональную активность и структуру сетчатки глаза кролика