Chicken retinal ganglion cells response characteristics: multi-channel electrode recording study

A fundamental question in neuroscience is how the information relevant to behavior is presented in the activity of neurons[1]. The visual system, especially the retina, offers some advantage to explore the neural code owing to its explicitly layered structure and relatively simple neuron types[2]. However, most of what we know about retinal signaling is derived from single neuron recordings[2,3]. The assumptions underlying this approach are that individual neuron acts as a unique element dedi…     

The development of intrinsic excitability in mouse retinal ganglion cells

Activity-dependent refinement of synaptic connections occurs throughout the developing nervous system, including the visual system. Retinal ganglion cells (RGCs) overproduce synapses then refine them in an activity-dependent manner that segregates RGC connections into multicellular patterns, such as eye-specific regions and retinotopic maps. Ferrets additionally segregate ON and OFF retinogeniculate pathways in an activity-dependent manner. It was unknown whether differences in ON versus OFF intrinsic and spontaneous activity occur in postnatal mouse. The work reported here measured the intrinsic properties and spontaneous activity of morphologically identified postnatal mouse RGCs, and tested the hypothesis that mouse ON and OFF RGCs develop differences in spontaneous activity. We found developmental changes in resting potential, action potential threshold, depolarization to threshold, action potential width, action potential patterns, and maximal firing rates. These results are consistent with the maturation of the intrinsic properties of RGCs extending through the first three postnatal weeks. However, there were no differences among mouse ON, OFF, and multistratified RGCs in intrinsic excitability, spontaneous synaptic drive or spontaneous action potential patterns. The absence of differences between ON and OFF activity patterns is unlike the differences that arise in ferrets. In contrast to the ferret, the ON and OFF target neurons in the mouse are organized in a random pattern, not layers. This supports the hypothesis that the absence of systematic differences in activity results in the nonlayered distribution of retinogeniculate connections.     

Autophagy promotes survival of retinal ganglion cells after optic nerve axotomy in mice

Autophagy is an essential recycling pathway implicated in neurodegeneration either as a pro-survival or a pro-death mechanism. Its role after axonal injury is still uncertain. Axotomy of the optic nerve is a classical model of neurodegeneration. It induces retinal ganglion cell death, a process also occurring in glaucoma and other optic neuropathies. We analyzed autophagy induction and cell survival following optic nerve transection (ONT) in mice. Our results demonstrate activation of autophagy shortly after axotomy with autophagosome formation, upregulation of the autophagy regulator Atg5 and apoptotic death of 50% of the retinal ganglion cells (RGCs) after 5 days. Genetic downregulation of autophagy using knockout mice for Atg4B (another regulator of autophagy) or with specific deletion of Atg5 in retinal ganglion cells, using the Atg5(flox/flox) mice reduces cell survival after ONT, whereas pharmacological induction of autophagy in vivo increases the number of surviving cells. In conclusion, our data support that autophagy has a cytoprotective role in RGCs after traumatic injury and may provide a new therapeutic strategy to ameliorate retinal diseases.     

Circadian regulation of phospholipid metabolism in retinal photoreceptors and ganglion cells

The neural retina is a key component of the vertebrate circadian system that is responsible for synchronizing the central circadian pacemaker to external light-dark (LD) cycles. The retina is itself rhythmic, showing circadian cycles in melatonin levels and gene expression. We assessed the in vivo incorporation of 32P-phosphate and 3H-glycerol into phospholipids of photoreceptor cells (PRCs) and retina ganglion cells (GCs) from chicks in constant illumination conditions (dark: DD or light: LL) over a 24-h period. Our findings showed that in DD there was a daily oscillation in 32P-labeling of total phospholipids synthesized in GCs and axonally transported to the brain. This metabolic fluctuation peaked during the subjective night (zeitgeber time [ZT] 20), persisted for several hours well into the subjective day and declined at subjective dusk (ZT 10-12). PRCs also exhibited an in vivo rhythm of 32P-phospholipid synthesis in DD. This rhythm peaked around ZT 22, continued a few hours into the day and declined by the end of subjective dusk. The major individual species labeled 1 h after 32P administration was phosphatidylinositol (PI) in both PRCs and GCs. Rhythmic phospholipid biosynthesis was also observed in DD after 3H-glycerol administration, with levels in GCs elevated from midday to early night. PRCs exhibited a similar rhythmic profile with the lowest levels of labeling during midnight. Phosphatidylcholine (PC) accounted for the individual species with the highest ratio of 3H-glycerol incorporation in both cell populations at all phases examined. By contrast, in LL the rhythm of 3H-glycerol labeling of phospholipids damped out in both cell layers. Our findings support the idea that, in constant darkness, the metabolism of retinal phospholipids, including their de novo biosynthesis, is regulated by an endogenous circadian clock.     

Electrical activity of rat retinal ganglion cells

The electrical activity of rat retinal ganglion cells is described. It was found that most such cells generate tonic discharges, while cells that demonstrate a phasic type of activity are less numerous. Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 382–384, July–October, 2007.     

Adenosine inhibits calcium channel currents via A1 receptors on salamander retinal ganglion cells in a mini-slice preparation

The effects of adenosine on high-voltage-activated calcium channel currents in tiger salamander retinal ganglion cells were investigated in a mini-slice preparation. Adenosine produced a concentration-dependent decrease in the amplitude of calcium channel current with a maximum inhibition of 26%. The effects of adenosine on calcium channel current were both time- and voltage-dependent. In cells dialyzed with GTP-gamma-s, adenosine caused a sustained and irreversible inhibition of calcium channel current, suggesting involvement of a GTP-binding protein. The inhibitory effect of adenosine on calcium channel current was blocked by the A1 antagonist 8-cyclopentyltheophylline (DPCPX, 1-10 microm), but not by the A2 antagonist 3-7-dimethyl-1-propargylxanthine (DMPX, 10 microm), and was mimicked by the A1 agonist N6-cyclohexyladenosine (CHA, 1 microm) but not by the A2 agonist 5'-(N-cyclopropyl) carbox-amidoadenosine (CPCA, 1 microm). Adenosine's inhibition of calcium channel current was not affected by the L-type calcium channel blocker nifedipine (5 microm). However, adenosine's inhibition of calcium channel current was reduced to approximately 10% after application of omega-conotoxin GVIA (1 microm), suggesting that adenosine inhibits N-type calcium channels. These results show that adenosine acts on an A1 adenosine receptor subtype via a G protein-coupled pathway to inhibit the component of calcium channel current carried in N-type calcium channels.     

Oxidative stress induces autophagy in response to multiple noxious stimuli in retinal ganglion cells

Retinal ganglion cells (RGCs) are the only afferent neurons that can transmit visual information to the brain. The death of RGCs occurs in the early stages of glaucoma, diabetic retinopathy, and many other retinal diseases. Autophagy is a highly conserved lysosomal pathway, which is crucial for maintaining cellular homeostasis and cell survival under stressful conditions. Research has established that autophagy exists in RGCs after increasing intraocular pressure (IOP), retinal ischemia, optic nerve transection (ONT), axotomy, or optic nerve crush. However, the mechanism responsible for defining how autophagy is induced in RGCs has not been elucidated. Accumulating data has pointed to an essential role of reactive oxygen species (ROS) in the activation of autophagy. RGCs have long axons with comparatively high densities of mitochondria. This makes them more sensitive to energy deficiency and vulnerable to oxidative stress. In this review, we explore the role of oxidative stress in the activation of autophagy in RGCs, and discuss the possible mechanisms that are involved in this process. We aim to provide a more theoretical basis of oxidative stress-induced autophagy, and provide innovative targets for therapeutic intervention in retinopathy.     

Oxidative stress induces autophagy in response to multiple noxious stimuli in retinal ganglion cells

Retinal ganglion cells (RGCs) are the only afferent neurons that can transmit visual information to the brain. The death of RGCs occurs in the early stages of glaucoma, diabetic retinopathy, and many other retinal diseases. Autophagy is a highly conserved lysosomal pathway, which is crucial for maintaining cellular homeostasis and cell survival under stressful conditions. Research has established that autophagy exists in RGCs after increasing intraocular pressure (IOP), retinal ischemia, optic nerve transection (ONT), axotomy, or optic nerve crush. However, the mechanism responsible for defining how autophagy is induced in RGCs has not been elucidated. Accumulating data has pointed to an essential role of reactive oxygen species (ROS) in the activation of autophagy. RGCs have long axons with comparatively high densities of mitochondria. This makes them more sensitive to energy deficiency and vulnerable to oxidative stress. In this review, we explore the role of oxidative stress in the activation of autophagy in RGCs, and discuss the possible mechanisms that are involved in this process. We aim to provide a more theoretical basis of oxidative stress-induced autophagy, and provide innovative targets for therapeutic intervention in retinopathy.     

Exogenous nitric oxide causes collapse of retinal ganglion cell axonal growth cones in vitro

We show that nitric oxide (NO) from applied NO-donating chemicals induces collapse of ganglion cell axonal growth cones extending from explants of tadpole retina in culture. Peroxynitrite, a neurotoxic product of NO and superoxide reaction, did not induce collapse, and oxyhemoglobin, which binds NO, blocked the highly effective collapsing activity of the NO donor S-nitrosocysteine. Membrane-permeable analogs of cyclic guanosine monophosphate had no collapsing activity. Inhibitors of NO synthase did not induce collapse. NO is a potential retrograde messenger through which postsynaptic neurons signal to their inputs to modify synaptic efficacy following NMDA receptor activation. Our results suggest a role for NO as such a messenger during development of the retinotectal projection. © 1996 John Wiley & Sons, Inc.     

Neuroprotective role of Nrf2 for retinal ganglion cells in ischemia‐reperfusion

Retinal ischemia plays a critical role in multiple vision‐threatening diseases and leads to death of retinal neurons, particularly ganglion cells. Oxidative stress plays an important role in this ganglion cell loss. Nrf2 (NF‐E2‐related factor 2) is a major regulator of the antioxidant response, and its role in the retina is increasingly appreciated. We investigated the potential retinal neuroprotective function of Nrf2 after ischemia‐reperfusion (I/R) injury. In an experimental model of retinal I/R, Nrf2 knockout mice exhibited much greater loss of neuronal cells in the ganglion cell layer than wild‐type mice. Primary retinal ganglion cells isolated from Nrf2 knockout mice exhibited decreased cell viability compared to wild‐type retinal ganglion cells, demonstrating the cell‐intrinsic protective role of Nrf2. The retinal neuronal cell line 661W exhibited reduced cell viability following siRNA‐mediated knockdown of Nrf2 under conditions of oxidative stress, and this was associated with exacerbation of increase in reactive oxygen species. The synthetic triterpenoid CDDO‐Im (2‐Cyano‐3,12‐dioxooleana‐1,9‐dien‐28‐imidazolide), a potent Nrf2 activator, inhibited reactive oxygen species increase in cultured 661W under oxidative stress conditions and increased neuronal cell survival after I/R injury in wild‐type, but not Nrf2 knockout mice. Our findings indicate that Nrf2 exhibits a retinal neuroprotective function in I/R and suggest that pharmacologic activation of Nrf2 could be a therapeutic strategy.

     

Up‐regulation of crystallins is involved in the neuroprotective effect of wolfberry on survival of retinal ganglion cells in rat ocular hypertension model

Wolfberry (fruit of Lycium barbarum Linn) has been known for balancing ‘Yin’ and ‘Yang’ in the body, nourishing the liver and kidney, improving visual acuity for more than 2,500 years in oriental countries. The active components in wolfberry include L. barbarum polysaccharide (LBP), zeaxanthine, betaine, cerebroside and trace amounts of zinc, iron, and copper. Each of them confers distinct beneficial effects and together they help to explain widespread use of wolfberry in the eastern world. Earlier study reported the neuroprotective effects of LBP on retinal ganglion cell (RGC) in an experimental model of glaucoma and the underlying in vivo cellular mechanisms of LBP neuroprotection deserve further exploration. In this study, we adopted proteomics, functional genomics, to evaluate pharmacological effects of LBP on the neuronal survival pathways. Among the significantly changed proteins induced by LBP feeding on ocular hypertension (OH) retinas, only proteins in crystallin family were focused in this study. The proteomic results were further confirmed using the Western blotting of the retinas and immunohistochemical staining of the retinal sections. We demonstrated that neuroprotective effect of—wolfberry extract—LBP on the survival of RGCs may be mediated via direct up‐regulation of neuronal survival signal βB2‐crystallin. J. Cell. Biochem. 110: 311–320, 2010. © 2010 Wiley‐Liss, Inc.     

Formation of functional synapses by regenerating adult rat retinal ganglion cell axons in midbrain target regions in vitro

The ability of adult rat retinal ganglion cell (RGC) axons to reinnervate normal target regions was examined in vitro. In co-culture experiments, adult rat retinal explants were placed adjacent to fetal rat midbrain sections that contained the superior colliculus (SC) which is the main target for RGC axons. Adult rat RGCs regrew axons over more than 500 μm on a polylysine-laminin substrate to reach the co-cultured explants. By using neurofilament immunohistochemistry and the fluorescent dye Dil for anterograde and retrograde tracing, it was shown that (1) adult rat RGCs with a stereotyped morphology survived in explant cultures for more than 4 weeks in the presence of fetal midbrain explants, (2) regenerating RGC axons preferentially terminated within midbrain target regions, and (3) RGCs formed functional synapses. In addition, the maturation of the SC region in midbrain explants was examined histologically and ultrastructurally to demonstrate appropiate target development. © 1993 John Wiley & Sons, Inc.     

Contribution of human melanopsin retinal ganglion cells to steady-state pupil responses

The recent discovery of melanopsin-containing retinal ganglion cells (mRGCs) has led to a fundamental reassessment of non-image forming processing, such as circadian photoentrainment and the pupillary light reflex. In the conventional view of retinal physiology, rods and cones were assumed to be the only photoreceptors in the eye and were, therefore, considered responsible for non-image processing. However, signals from mRGCs contribute to this non-image forming processing along with cone-mediated luminance signals; although both signals contribute, it is unclear how these signals are summed. We designed and built a novel multi-primary stimulation system to stimulate mRGCs independently of other photoreceptors using a silent-substitution technique within a bright steady background. The system allows direct measurements of pupillary functions for mRGCs and cones. We observed a significant change in steady-state pupil diameter when we varied the excitation of mRGC alone, with no change in luminance and colour. Furthermore, the change in pupil diameter induced by mRGCs was larger than that induced by a variation in luminance alone: that is, for a bright steady background, the mRGC signals contribute to the pupillary pathway by a factor of three times more than the L- and M-cone signals.     

Intrinsically photosensitive retinal ganglion cells

A new mammalian photoreceptor was recently discovered to reside in the ganglion cell layer of the inner retina.These intrinsically photosensitive retinal ganglion cells(ipRGCs) express a photopigment,melanopsin,that confers upon them the ability to respond to light in the absence of all rod and cone photoreceptor input.Although relatively few in number,ipRGCs extend their dendrites across large expanses of the retina making them ideally suited to function as irradiance detectors to assess changes in ambient...     

光学方法同步记录成群前庭神经节细胞膜电位

目的 :采用电压敏感染料和多位点光学成像系统研究前庭神经节细胞 (vestibularganglioncells ,VGCs)电生理特性。方法 :自新生小鼠内耳分离并培养的VGCs ,用吸光性电压敏感染料RH15 5染色后 ,多个或成群VGCs被同时成像于 16× 16记录单元Photodiodearrays (PDA)光学成像系统。 结果 :用高钾溶液灌流刺激时发现当VGCs膜电位变化时 ,膜表面的光吸收增强 ,光吸收度为 0 .2 3%± 0 .0 8%。并且所记录的光学反应具有波长特性。另外 ,在本实验条件下 ,光损伤和染料的药毒性副作用不明显或者可忽略不计。结论 :光学记录可以同步观测多个和成群VGCs膜电位变化 ,是电生理研究的新方法     

视网膜神经节细胞的协同活动以及信息编码

在脊椎动物的视觉系统中,信息的初级处理发生在视网膜.随着多电极记录技术的发展,视网膜神经节细胞的协同活动在不同物种中被广泛地观察到.然而,协同活动在视觉信息处理中的作用还不清楚,并且存在一定的争议.本文回顾了近些年关于视网膜神经节细胞协同活动的相关研究,对协同活动的分类、检测以及生理功能进行讨论.     

Changing dendritic field size of mouse retinal ganglion cells in early postnatal development

During early postnatal development, dendrites of retinal ganglion cells (RGCs) extend and branch in the inner plexiform layer to establish the adult level of stratification, pattern of branching, and coverage. Many studies have described the branching patterns, transient features, and regulatory factors of stratification of the RGCs. The rate of RGC dendritic field (DF) expansion relative to the growing retina has not been systematically investigated. In this study, we used two methods to examine the relative expansion of RGC DFs. First, we measured the size of RGC DFs and the diameters of the eyeballs at several postnatal stages. We compared the measurements with the RGC DF sizes calculated from difference of the eyeball sizes based on a linear expansion assumption. Second, we used the number of cholinergic amacrine cells (SACs) circumscribed by the DFs of RGCs at corresponding time points as an internal ruler to assess the size of DFs. We found most RGCs exhibit a phase of faster expansion relative to the retina between postnatal day 8 (P8) and P13, followed by a phase of retraction between P13 and adulthood. The morphological α cells showed the faster growing phase but not the retraction phase, whereas the morphological ON–OFF direction selective ganglion cells expanded in the same pace as the growing retina. These findings indicate different RGCs show different modes of growth, whereas most subtypes exhibit a fast expansion followed by a retraction phase to reach the adult size. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 397–407, 2010     

Exenatide prevents high-glucose-induced damage of retinal ganglion cells through a mitochondrial mechanism

Exenatide (exendin-4 analogue) is widely used in clinics and shows a neuroprotective effect. The main objectives of the present study were to prove that retinal ganglion cells (RGC-5) express GLP-1R, to ascertain whether exenatide prevents a high-glucose-induced RGC-5 impairment, to determine the appropriate concentration of exenatide to protect RGC-5 cells, and to explore the neuroprotective mechanisms of exenatide. Immunofluorescence and Western blot analyses demonstrated that RGC-5 cells express GLP-1R. We incubated RGC-5 cells with 25 mM glucose prior to incubation with either 25 mM glucose, 55 mM glucose (high), high glucose plus exenatide or high glucose plus a GLP-1R antagonist. The survival rates of the cells were measured by CCK-8, and cellular injury was detected by electron microscopy. There were statistical differences between the high-glucose group and the control group (P<0.05). Exenatide improved the survival rate of the cells and suppressed changes in the mitochondrial morphology. The optimum concentration of exenatide to protect the RGC-5 cells from high-glucose-induced RGC injury was 0.5 μg/ml, and this protective effect could be inhibited by exendin (9-39). To further study the mechanism underlying the beneficial effects of exenatide, the expression levels of cytochrome c, Bcl-2, Bax and caspase-3 were analysed by Western blot. The present study showed that treatment with exenatide significantly inhibited cytochrome c release and decreased the intracellular expression levels of Bax and caspase-3, whereas Bcl-2 was increased (P<0.05). These results suggested that GLP-1R activation can inhibit the cellular damage that is induced by high glucose. A mitochondrial mechanism might play a key role in the protective effect of exenatide on the RGC-5 cells, and exenatide might be beneficial for patients with diabetic retinopathy.