For the investigation of the receptive field of the retinal neurons, the spatial and temporal properties of horizontal cells and the center-surround antagonisms of bipolar cells and the third-order neurons were studied using conventional intracellular recording techniques. Horizontal cells were hyperpolarized by the large annulus light stimuli (id: 3.5mm) and required at least 0.2 seconds of dark periods to respond enough. The amplitudes of the response of the ON-bipolar cell were decreased as the diameter of the spot stimuli was increased to 2.6mm and the responses were inverted at 2.6mm of inner diameter of the spreading annulus stimuli with fixed width. ON-sustained cell with spikes generated ON-sustained light responses by small annulus (1400-2100micrometer), but elicited OFF-sustained responses by large annulus (2100-2800micrometer). ON-sustained cell without spikes also showed surround antagonism. The spikes were generated at the spot of 490micrometer diameter and they were disappeared at the spot of 5600micrometer diameter. And, OFF-transient component of the ON-OFF transient cell was enhanced as annulus stimuli spread. The results suggest that the horizontal cells have large and monotonic receptive fields while the bipolar cells and the ON-sustained cells have large biphasic receptive fields in the catfish retina.
Catfishes* ; Neurons* ; Retina ; Retinal Neurons

Müller glia (MG) are the primary support cells in the vertebrate retina, regulating homeostasis in one of the most metabolically active tissues. In lower vertebrates such as fish, they respond to injury by proliferating and reprogramming to regenerate retinal neurons. In mammals, MG may also react to injury by proliferating, but they fail to initiate regeneration. The barriers to regeneration could be intrinsic to mammalian MG or the function of the niche that cannot support the MG reprogramming required for lineage conversion or both. Understanding these mechanisms in light of those being discovered in fish may lead to the formulation of strategies to unlock the neurogenic potential of MG and restore regeneration in the mammalian retina.
Homeostasis ; Mammals ; Neurogenesis ; Neuroglia* ; Regeneration ; Retina ; Retinal Neurons ; Vertebrates

Horizontal cells (HCs) of the mammalian retina are interneurons that provide negative feedback to photoreceptors in the outer plexiform layer (OPL) where the first synapse occurs and contribute to the center surround antagonism that underlies the receptive field properties of many retinal neurons. These functions of HCs are thought to be attributed to their coupled network via gap junctions. Two kinds of connexin (Cx) proteins, Cx50 and 57 are known to form gap junctions of HCs. However, little is known about precise localization of gap junctions within HCs. Thus, this study was designed to determine the localization of HC gap junctions at subcellular level. In vertical ultrathin sections of the rabbit retina, gap junctions composed of Cx50 and 57 were identified in the OPL by the electron-dense reaction products. Each Cx50 and 57 gap junction on putative HC processes showed its own distinct features. Cx50 gap junction was bigger in size and localized more proximally than Cx57. In addition, Cx57 gap junctions had distinct shape. That is, about a half of them appeared to be invaginated or endocytosed in shape. The differences in shape, size and subcellular localization between Cx50 and 57 gap junctions may provide the insights into the function of different types of horizontal cell.
Gap Junctions ; Interneurons ; Proteins ; Retina ; Retinal Neurons ; Synapses

The role of GABA or glycine as an inhibitory neurotransmitter is well established, and GABAergic or glycinergic neurons appear to play an important role in the mammalian retinas. It has been reported that certain amacrine, bipolar, displaced amacrine and ganglion cells are consistently labeled with anti-GABA or anti-glycine antisera in the mammalian retinae so far, and it has been suggested that colocalization of GABA and glycine within the retinal neurons could be common in the mammalian retina by recent immunecytochemical and electrophysiological studies. This study was conducted to localize GABAergic and glycinergic neurons and to define whether GABA and glycine are colocalized within same retinal neurons of the rat retina by immunocytochemical method using anti-GABA and anti-glycine antisera. The results were as follows : 1. GABAergic neurons of the rat retina were amacrine, interplexiform, bipolar, displaced amacrine and ganglion cells, and processes of GABAergic neurons formed dense networks with distinct two bands in the inner plexiform layer. 2. Glycinergic neurons were amacrine, bipolar, displaced amacrine and ganglion cells,and their processes were evenly distributed as dense networks through whole inner plexiform layer. 3. 28.5% of GABA immunoreactive amacrine cells and 9.8% of GABA immunoreactive bipolar cells located in the inner nuclear layer,and 11.9% of labeled neurons located in the ganglion cell layer showed glycine immunoreactivity in the rat retina. These results demonstrate that GABA and glycine, major inhibitory neurotransmitters, are colocalized within certain amacrine and displaced amacrine cells, and a few bipolar cells, and that neurons synthesizing and utilizing both GABA and glycine as their neurotransmitters may play an unique role in the visual processing in the rat retina.
Amacrine Cells ; Animals ; GABAergic Neurons ; gamma-Aminobutyric Acid* ; Ganglion Cysts ; Glycine* ; Immune Sera ; Neurons* ; Neurotransmitter Agents ; Rats* ; Retina* ; Retinal Neurons

We used an animal model of laser-induced retinal vein occlusion to study the temporal and spatial patterns of neuronal necrosis and apoptosis. After photodynamic retinal vein thrombosis with argon-green laser, rats were sacrificed at 6 hours, 12 hours, 1 day, 2 days, 3 days, 5 days, 7 days, and 14 days after vein occlusion. The temporal and spatial patterns of neuronal cell death were determined using light and electron microscopy, TdT-dUTP nick-end labeling[TUNEL]and DNA gel electrophoresis. The cells in retinal ganglion cell layer and inner nuclear layer showed both necrotic and apoptotic changes 12 hours after vein occlusion. The TUNEL positivity were detected at day 1 after vein occlusion and the number of positive cell increased until day 2, and decreased thereafter. DNA ladder pattern was observed 48 hours after vein occlusion by DNA gel electrophoreisis. These data demonstrated that retinal vein occlusion induces necrosis and apoptosis in the retinal ganglion cell and inner nuclear layer.
Animals ; Apoptosis ; Cell Death* ; DNA ; Electrophoresis ; In Situ Nick-End Labeling ; Microscopy, Electron ; Models, Animal ; Necrosis ; Neurons ; Rats ; Retinal Ganglion Cells ; Retinal Vein Occlusion* ; Retinal Vein* ; Retinaldehyde* ; Veins

We used an animal model of laser-induced retinal vein occlusion to study the temporal and spatial patterns of neuronal necrosis and apoptosis. After photodynamic retinal vein thrombosis with argon-green laser, rats were sacrificed at 6 hours, 12 hours, 1 day, 2 days, 3 days, 5 days, 7 days, and 14 days after vein occlusion. The temporal and spatial patterns of neuronal cell death were determined using light and electron microscopy, TdT-dUTP nick-end labeling[TUNEL]and DNA gel electrophoresis. The cells in retinal ganglion cell layer and inner nuclear layer showed both necrotic and apoptotic changes 12 hours after vein occlusion. The TUNEL positivity were detected at day 1 after vein occlusion and the number of positive cell increased until day 2, and decreased thereafter. DNA ladder pattern was observed 48 hours after vein occlusion by DNA gel electrophoreisis. These data demonstrated that retinal vein occlusion induces necrosis and apoptosis in the retinal ganglion cell and inner nuclear layer.
Animals ; Apoptosis ; Cell Death* ; DNA ; Electrophoresis ; In Situ Nick-End Labeling ; Microscopy, Electron ; Models, Animal ; Necrosis ; Neurons ; Rats ; Retinal Ganglion Cells ; Retinal Vein Occlusion* ; Retinal Vein* ; Retinaldehyde* ; Veins

Nitric oxide(NO) is a free radical which serves a wide variety of functions on vascular tone, neurotransmission, immune cytotoxicity, and many others. Nitric oxide synthase(NOS) is the biosynthetic enzyme of NO and colocalized with NADPH diaphorase(NADPH-d) activity in many tissues. The author aimed to assess the changes that occur in this populations of neurons in the streptozotocin-induced diabetic rat where the retinal vasculature is known to be dysfunctional. The 8 rats was a diabetic group and the other 8 was a control group. Diabetes was induced with a single intraperitoneal injection of streptozotocin(65mg/kg). Four weeks later, the retina was flat mounted and stained with NADPH-d. Counting of the stained cells was made. There was a 20.6% decrease in the total number of positively staining cells in the retinas of the diabetic group(2532+/-192) compared with those of the control group(3188+/-176)(p<0.001). It is worth to suggest the close correlation between NO released from retinal neurons and the microcirculatory dysfunction in diabetic retinopathy.
Animals ; Diabetic Retinopathy ; Injections, Intraperitoneal ; NADP* ; NADPH Dehydrogenase* ; Neurons ; Nitric Oxide ; Rats* ; Retina* ; Retinal Neurons ; Retinaldehyde* ; Synaptic Transmission

To investigate the mechanism of the excitatory signal transmission, the effects of N-methyl-D-aspartate(NMDA, ionotropic glutamate agonist) and kynurenic acid(glutamate antagonist) on catfish retinal neurons were explored using conventional intracellular recording techniques. Horizontal cells were depolarized by glutamate, kainate, quisqualate, and NMDA but gyperpolarized by kynurenate. Transient components of both ON-and OFF-bipolar cells were reduced either by glutamate or by NMDA. Kynurenate suppressed sustained components of the third-order neurons or OFF-bipolar cells. Furthermore, kynurenate blocked the depolarizing actions of NMDA on horizontal cells and ON-sustained cells with large ON-transient components. The results suggest that NMDA would exert a tonic depolarization in the horizontal cells and the 3rd-order neurons, and there might be a preferential suppression on the a NMDA receptors by kynurenic acid in the catfish retina.
Catfishes ; Glutamic Acid ; Kainic Acid ; Kynurenic Acid* ; N-Methylaspartate ; Neurons* ; Quisqualic Acid ; Receptors, N-Methyl-D-Aspartate ; Retina* ; Retinal Neurons

Since the output of retina for visual stimulus is carried by neurons of very diverse functional properties, it is not adequate to use conventional single electrode for recording the retinal action potential. For this purpose, we used newly developed multichannel recording system for monitoring the simultaneous electrical activities of many neurons in a functioning piece of retina. Retinal action potentials are recorded with an extra-cellular planar array of 60 microelectrodes. In studying the collective activity of the ganglion cell population it is essential to recognize basic functional distinctions between individual neurons. Therefore, it is necessary to detect and to classify the action potential of each ganglion cell out of mixed signal. We programmed M-files with MATLAB for this sorting process. This processing is mandatory for further analysis, e.g. poststimulus time histogram (PSTH), auto-correlogram, and cross-correlogram. We established MATLAB based protocol for waveform classification and verified that this approach was effective as an initial spike sorting method.
Action Potentials ; Classification ; Electrodes ; Ganglion Cysts ; Microelectrodes ; Neurons ; Retina ; Retinal Ganglion Cells* ; Retinaldehyde*

PURPOSE: To determine the loss of ganglion cell layer (GCL) neurons in patients with age-related macular degeneration (AMD) with choroidal neovascularization (CNV). METHODS: Retinal nerve fiber layer (RNFL) photography was taken in patients with AMD with CNV to assess the presence of RNFL defects in the papillomacular bundle area. Patients with other ocular disorders or a history of previous intraocular surgery or laser treatment were excluded from this study. RESULTS: Eighty-five eyes in 65 patients were included, of which only one (1.2%) showed papillomacular bundle defects in association with CNV. CONCLUSIONS: From this study, the majority of the patients with AMD with CNV had no papillomacular bundle defect, which demonstrates that considerable amount of GCL is maintained in AMD.
Choroidal Neovascularization ; Ganglion Cysts ; Humans ; Macular Degeneration* ; Nerve Fibers* ; Neurons ; Photography* ; Retinal Ganglion Cells* ; Retinaldehyde*