非成像视觉环路对生理活动和行为的调控作用

视网膜神经节细胞(RGCs)是视网膜视觉信号输出到大脑的终极神经元, 可参与成像视觉(IFV)(图像形成)和非成像视觉(NIFV)(非图像形成)。视觉处理系统除了传递图像的视觉信息外, 传入的光信号对人的生理活动和行为也会产生影响, 称为NIFV。NIFV较少依赖于传统光感受器细胞产生的信号, 而是由视网膜上一类特殊的视网膜感光神经节细胞(ipRGCs)来完成。ipRGCs是RGCs中一类能表达感光黑视蛋白的细胞, 其轴突投射至特定核团, 参与调控多种NIFV行为, 从基础生理调节(如心率和瞳孔大小)到更复杂的行为调节(如昼夜节律), 甚至更高层次的认知过程(如焦虑等情绪)。NIFV环路是对光的重要反应, ipRGCs在NIFV环路中起着至关重要的作用。本文就NIFV环路对生理活动和行为的调控作用进行综述, 归纳ipRGCs投射核团与NIFV功能的关系, 以期为临床医生提供更加全面的视觉认识。     

视网膜感光神经节细胞研究进展

视网膜感光神经节细胞（intrinsically photosensitive retinal ganglion cells，ipRGCs）是哺乳动物视网膜上一种特殊类型的神经节细胞，它能表达一种视网膜色素蛋白即黑视素蛋白，因此具备自主对光产生反应的能力。ipRGCs本质上是光敏细胞，参与成像和非成像视觉过程。本文对ipRGCs的细胞分类、信号转导、中枢投射、生理功能以及其在疾病研究中最新的研究进展进行综述。     

斑马鱼视网膜感光细胞的发育及视蛋白的表达

目的研究斑马鱼视网膜感光细胞的发育和视蛋白的表达，明确利用斑马鱼研究视网膜和感光细胞的可行性。方法制备斑马鱼视网膜感光细胞视蛋白（视杆细胞视紫质、视锥细胞紫外线视蛋白和视锥细胞蓝色视蛋白）的RNA探针。收集受精后72，96，120h的斑马鱼眼球组织进行切片、电镜观察和整体原位杂交。结果斑马鱼的神经视网膜分层排列，包括3个细胞层和2个丛状层。随时间发展，视网膜的发育逐渐成熟，3个细胞层的细胞排列更加整齐，感光细胞的外节盘发育更加成熟，3种视蛋白的表达逐渐增强，范围扩大。结论利用斑马鱼进行视网膜和感光细胞的研究是可行的，视蛋白可作为感光细胞的标记。     

内在光敏性视网膜神经节细胞研究现状与展望

内在光敏性视网膜神经节细胞(ipRGC)是近20a来新发现的一类感光细胞。它们通过视色素黑视蛋白发挥感光功能，并将光信号传递至非成像功能脑区如视交叉上核(SCN)、橄榄前盖核(OPN)以控制昼夜节律光夹带和瞳孔对光反射； 还有少部分信号投射至大脑成像区域如背外侧膝状核(dLGN)和上丘(SC)参与成像视觉。目前已发现6种ipRGC亚型(M1～M6)，每种亚型都具有独特的形态和生理特性。这些细胞除了接收来自视杆细胞和视锥细胞的信号输入，也在视网膜内部通过化学突触和电突触调节视网膜内信号转导，在视觉信号传递和视觉发育中发挥重要作用。研究发现ipRGC与多种眼科及全身性疾病存在重要联系。由此可见这是一类复杂且重要的细胞类型，本文从ipRGC的发现、一般生理特性、信号转导和与疾病的关系等多方面进行综述。     

新感光视蛋白视黑质的研究进展

视黑质是一种新近发现的、主要分布于视网膜神经节细胞的光感受器视蛋白,这一发现打破了一直以来持有的光感受器视蛋白仅分布于视杆和视锥细胞的观点。与经典的感光视蛋白功能不同,视黑质的主要功能是参与引发昼夜节律变化、瞳孔对光反应、体内激素水平的变化等非视觉成像光反应。本文就视黑质的形态和功能特点等作一综述。     

视网膜色素变性患者视锥和视杆细胞多焦视网膜电图检测

目的 观察视网膜色素变性(RP)患者视锥细胞和视杆细胞的多焦视网膜电图(mfERG)特征.评估感光细胞功能.方法 选取正常受试者8例8只眼进行视杆细胞mfERG检查.分析不同刺激光亮度对P1波振幅的影响;对19例RP患者38只眼分别进行视杆和视锥细胞mfERG检查.根据局部波形信噪比判断检出率,对视锥细胞mfERG不同类型间的平均视力、P1波振幅惭度进行比较和统计学分析.同时对比分析RP患者视杆和视锥细胞mfERG在各象限P1波振幅的变化.结果 采用0.04 cd/m~2蓝色低刺激光亮度可以稳定记录正常人视杆细胞mfERG反应.RP患者视锥和视杆细胞mfERG有效波形检出率分别为65.79%和10.51%.视锥mfERG I型P1波振幅密度高于Ⅱ型,差异有统计学意义(t=5.21,P=0.0000),平均视力差异无统汁学意义(t=1.15,P=0.612).I型振幅密度与logMAR视力呈负相关(r=-0.48,P=0.04).分别比较RP患者视锥和视杆mfERG局部波形特征发现,两者在各象限的P_1振幅密度在空间上有一定的对应性.结论 RP患者黄斑区视锥细胞的反应存在多样性,视锥细胞mfERG检出率高于视杆细胞,残存视锥和视杆细胞功能在空间上有一定的对应性.     

OTX2和CRX调控视网膜光感受器细胞发育分化的研究进展

视网膜感受器细胞可以将光信号转化为电信号,从而产生视觉。哺乳动物的光感受器细胞包括视锥细胞和视杆细胞。视锥细胞和视杆细胞的发育受多种调控因子的作用,其中,转录因子ＯＴＸ２和ＣＲＸ对视锥细胞和视杆细胞的发育分化和功能维持起着至关重要的作用。本文综述ＯＴＸ２和ＣＲＸ在视网膜光感受器细胞发育分化中的关键机制,为研究视网膜疾病的发生机制和干预治疗提供理论基础。     

试题与解答

1.在视网膜部,色觉信息处理是通过: A.三种类型视锥细胞; B.两种视锥细胞和视杆细胞相互作用; C.含黑色素视蛋白的神经节细胞; D.Blobs.     

视锥细胞营养不良七例报告

本文报道了七例视锥细胞营养不良病人,均双眼患病,眼底黄斑部呈青灰色伴有金箔样反光,视网膜脉络膜萎缩和色素沉着,以及视网膜血管变细等改变。荧光造影显示黄斑部靶心样或弥漫性色素上皮脱失,色素上皮和脉络膜毛细血管萎缩,色素遮蔽荧光和视网膜血管变细等改变。全视野 ERG 明视反应均明显降低或熄灭,暗视反应可正常、降低或熄灭。暗适应曲线呈现视锥细胞阈值明显升高,视杆细胞阈值正常或升高。色觉检查呈全色盲。结果表明本病以视锥细胞受损为主,伴有不同程度的视杆细胞损害。视功能的检查,尤其是全视野 ERG 和暗适应的测定,对本病的诊断具有重要的意义。     

对视网膜细胞蛋白合成的加龄变化研究

应用光镜放射自显技术的胎生期至生后一年鼠的视网膜各层细胞的蛋白合成变化进行了研究，结果表明，视杆，视锥细胞生后至一年始终保持着旺盛的蛋白合成功能，胎生期至生后一周，视杆，视锥细胞处于不成熟的分化阶段，视网膜各层细胞的胞核及胞质内切可见记颗粒，生后第一天其标记率出现第一个高峰，视杆，视锥和双极细胞分化成熟后，可见标记颗粒主要分布在视细胞的胞体，内节及双极细胞的胞质内，且视细胞的标记颗粒多于双极细胞，     

The influence of intrinsically-photosensitive retinal ganglion cells on the spectral sensitivity and response dynamics of the human pupillary light reflex

Historically, it was assumed that the light-evoked neural signals driving the human pupillary light reflex (PLR) originated exclusively from rod and cone photoreceptors. However, a novel melanopsin-containing photoreceptive cell class has recently been discovered in the mammalian retina. These intrinsically-photosensitive retinal ganglion cells (ipRGCs) project to the pretectum, the retinorecipient area of the brain responsible for the PLR. This study was therefore designed to examine the relative contribution of rod, cone and the melanopsin photoresponses of ipRGCs to the human PLR. We establish that the melanopsin photoresponse of ipRGCs contributes significantly to the maintenance of half maximal pupilloconstriction in response to light stimuli of 30 s or longer, even at low photopic irradiances. Furthermore, we show that the melanopsin photoresponse contributes significantly to three-quarter maximal pupilloconstriction in response to light stimuli as short as 2 s. We also demonstrate that cone photoresponses driving pupilloconstriction adapt considerably and contribute little after 30 s, but rod photoresponses adapt less and contribute significantly to the maintenance of pupilloconstriction in response to steady-state light stimuli at irradiance levels which are below the threshold of the melanopsin photoresponse.     

Synaptic contact between melanopsin-containing retinal ganglion cells and rod bipolar cells

PURPOSE: Evidence indicates that the melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) receive input from rods and cones, which are thought to modulate the irradiance detecting system driving entrainment of the circadian system and pupillomotor control. This study was performed to identify retinal cells that have synaptic contact with ipRGCs. METHODS: Immunohistochemistry and high-power confocal microscopy were used to generate stacks of digital images of sections stained with antibodies against melanopsin, protein kinase C (PKCalpha), tyrosine hydroxylase (TH), presynaptic terminal markers (C-terminal binding protein 2 [CtBP2], vesicular monoamine transporter 2 [VMAT2] and postsynaptic marker (glutamate receptor subunit 4 [GluR4]). Results were analyzed in a computer-based three-dimensional reconstruction program for cellular contacts. RESULTS: Markers and melanopsin rod bipolar processes were found to have axosomatic and axodendritic contact with melanopsin-containing RGCs. Typically, three to four contacts were found on the soma of the melanopsin-containing RGCs, together with contacts on proximal dendrites. Contacts visualized by only CtBP2 immunoreactivity could also be demonstrated on melanopsin cell bodies and processes representing contacts with other types of bipolar cells. At the border of the inner plexiform layer (IPL) and inner nuclear layer (INL), where melanopsin processes stratify, contacts between melanopsin and TH or VMAT2 immunoreactivity processes were observed. CONCLUSIONS: Through confocal microscopy and computer-based three-dimensional analyses, this study demonstrates that melanopsin-containing RGCs have synaptic contact with PKC/CtBP2-containing rod bipolar cells and TH/VMAT2-immunoreactive amacrine cells through axodendritic and axosomatic contact, supporting electrophysiological observations that rods and cones signal to the melanopsin-containing intrinsically photosensitive RGCs.     

The effect of controlled photopigment excitations on pupil aperture

In addition to rods and cones, the human retina contains melanopsin which has been identified recently in the body and dendrites of a few ganglion cells. The intrinsically photosensitive retinal ganglion cells (ipRGCs) are good candidates for controlling the tonic pupil aperture but their spectral sensitivity is close to those of rods and S‐cones which are other candidates. Our study aims at identifying the stimulus for the pupil response when the luminance is constant and the spectrum of the light changes. A light booth was equipped with five types of coloured light emitting diodes (LEDs): Blue, Cyan, Green, Orange and Red. The intensity of each LED type could be adjusted to control the light spectrum. Illumination pairs were prepared ensuring the exclusive variation of excitation of one receptor type and silent substitution for others. Because the range of the possible controlled changes of excitation was narrow, we also prepared illumination pairs ensuring silent substitution for luminance rather than for L‐cones and M‐cones independently. Photographs of the observer’s eyes were taken following one minute of adaptation to each illumination and the ratio of pupil to iris diameter was measured. No differential pupillary response was observed with a variation of rod, melanopsin or S‐cone excitation alone. A differential pupillary response could only be obtained with a variation of the melanopsin stimulus of sufficient high contrast with or without a concurrent variation of rods.     

Chromatic Pupillometry Dissects Function of the Three Different Light-Sensitive Retinal Cell Populations in RPE65 Deficiency

Purpose. The aim of the study was to objectively characterize the function of rods, cones, and intrinsic photosensitive retinal ganglion cells (ipRGCs) in patients with RPE65 mutations by using two published protocols for chromatic pupillometry, and to correlate the data with the clinical phenotype. Methods. The study group comprised 11 patients with RPE65 mutations, and for control purposes, 32 healthy probands and 2 achromats. A custom-made binocular chromatic pupillometer (Bino I) connected to a ColorDome Ganzfeld stimulator was used to assess changes in pupil diameter in response to red (640 nm) and blue (462 nm) light stimuli. Light intensities, stimulus duration, and background varied depending on the protocol used. Results were compared to the clinical phenotype, that is, visual field (Goldmann perimetry), best corrected visual acuity, and full-field stimulus testing (FST). Results. No significant differences in any of the pupil response parameters were observed in intraday or intervisit variability tests. Pupil responses to rod-weighted stimulation were significantly diminished in all RPE65 patients. Pupil responses to cone-weighted stimuli differed among RPE65 patients and did not always correlate with residual visual field and cone sensitivity loss in FST. Pupil responses to ipRGC-weighted answers were slightly but significantly diminished, and the postillumination pupil response was significantly increased. Conclusions. Chromatic pupillometry represents a highly sensitive and objective test to quantify the function of rods, cones, and ipRGCs in patients with RPE65 mutations.     

Melanopsin-dependent persistence and photopotentiation of murine pupillary light responses

PURPOSE: To determine the relative contributions of inner and outer retinal photoreception to the pupillary light response. METHODS: Wild-type, retinal degenerate (rd/rd), and melanopsin mutant (opn4(-/-)) mice were tested for pupillary light responsiveness by video pupillometry before, during, and after exposure to supersaturating light intensities. Similar lighting protocols were used to probe responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) recorded with multielectrode arrays ex vivo. RESULTS: Both outer retinal photoreceptors (rods and cones) and inner retinal photoreceptors (intrinsically photosensitive retinal ganglion cells [ipRGCs]) are sufficient to drive the pupillary light response in mice. After supersaturating light exposure, rather than bleaching or adapting, rd/rd mice showed paradoxical potentiation of responses to subsaturating light exposure. opn4(-/-) mice, in contrast, could not sustain pupillary constriction under continuous bright illumination, and showed desensitization after bright-light exposure. Both the intensity of light necessary to induce potentiation and the spectral sensitivity for sustained and potentiated responses differed from that necessary to trigger pupillary constriction, suggesting that photopotentiation is dependent on a pigment-state distinct from that triggering the pupillary light response itself. Multielectrode array recordings of ipRGCs from rd/rd retinas demonstrated persistent cell firing under continuous light exposure but did not show potentiation. CONCLUSIONS: Unique photoreceptive properties of intrinsically photosensitive RGCs confer resistance to bleaching and/or adaptation under continuous bright illumination to the pupillary light response and suggest the presence of a photopigment with multiple absorption states.     

Toward a clinical protocol for assessing rod, cone, and melanopsin contributions to the human pupil response

PURPOSE. To better understand the relative contributions of rod, cone, and melanopsin to the human pupillary light reflex (PLR) and to determine the optimal conditions for assessing the health of the rod, cone, and melanopsin pathways with a relatively brief clinical protocol. METHODS. PLR was measured with an eye tracker, and stimuli were controlled with a Ganzfeld system. In experiment 1, 2.5 log cd/m(2) red (640 ± 10 nm) and blue (467 ± 17 nm) stimuli of various durations were presented after dark adaptation. In experiments 2 and 3, 1-second red and blue stimuli were presented at different intensity levels in the dark (experiment 2) or on a 0.78 log cd/m(2) blue background (experiment 3). Based on the results of experiments 1 to 3, a clinical protocol was designed and tested on healthy control subjects and patients with retinitis pigmentosa and Leber's congenital amaurosis. RESULTS. The duration for producing the optimal melanopsin-driven sustained pupil response after termination of an intense blue stimulus was 1 second. PLR rod- and melanopsin-driven components are best studied with low- and high-intensity flashes, respectively, presented in the dark (experiment 2). A blue background suppressed rod and melanopsin responses, making it easy to assess the cone contribution with a red flash (experiment 3). With the clinical protocol, robust melanopsin responses could be seen in patients with few or no contributions from the rods and cones. CONCLUSIONS. It is possible to assess the rod, cone, and melanopsin contributions to the PLR with blue flashes at two or three intensity levels in the dark and one red flash on a blue background.     

Morphology of intrinsically photosensitive retinal ganglion cells: distinct photoreceptors from rod/cone photoreceptors北大核心CSCD

Objective: This study was to observe the morphology of live intrinsically photosensitive retinal ganglion cells (ipRGCs) at cellular level, and to explore their three-dimensional structure and responses to light in curved retina and the relationship with rod/cone photoreceptors. Methods: ipRGCs were identified according to the enhanced green fluorescent potein (EGFP) markers. Two hundred and sixty-three ipRGCs were videoed in mouse whole-mounted retina after strengthening with Lucifer Yellow from patch clamp electrodes. The dendrites and cell bodies were analyzed according to their sublayer-specific localization in inner plexiform layer and ganglion cell layer of curved retina. The relationship with rod/cone system was reconstructed and their functions were speculated. The animal feeding and use was in accordance with the standards set by the ARVO, and the experiment was approved by the Ethic Committee for Experimental Animal of Hubei University of Science and Technology. Results: The ipRGCs had strictly sublayer-specific localization in three sublayers of retinal inner plexiform layer. Each sublayer occupies full retina and form photosensitive surface, without any intermediate photosensitive dentric distribution between sublayers. Each ipRGC had randomly dentric distributions among the three sublayer curves, without the specific ON/OFF stratification. The photosensitive sublayers had absolutely perpendicular assignment related to cone/rod photoreceptors. The expression of melanopsin and spike-producing Ca2+ /Na+ channels were randomly distributed in M1, M2 and M3 cells. M4 and M5 cells shared the characteristic properties of conventional ganglion cells. Conclusions: In contrast to the rod/cone photoreceptors, ipRGCs form multiple-sublayer photosensitive curved surface, which are perpendicular to rod/cone photoreceptors, their photosensitive melanopsin and intrinsic spike-producing channels randomly occupy these specific sublayers, which suggest their distinct functions from rod/cone photoreceptors. Copyright © 2018 by the Chinese Medical Association.     

Unique functional properties of the APB sensitive and insensitive rod pathways signaling light decrements in mouse retinal ganglion cells

Light decrements are mediated by two distinct groups of rod pathways in the dark-adapted retina that can be differentiated on the basis of their sensitivity to the glutamate agonist DL-2-amino-phosphonobutyric (APB). By means of the APB sensitive pathway, rods transmit light decrements via rod bipolar cells to AII amacrine cells, then to Off cone bipolar cells, which in turn innervate the dendrites of Off ganglion cells. APB hyperpolarizes rod bipolar cells, thus blocking this rod pathway. With APB insensitive pathways, rods either directly synapse onto Off cone bipolar cells, or rods pass light decrement signal to cones by gap junctions. In the present study, whole-cell patch-clamp recordings were made from ganglion cells in the dark-adapted mouse retina to investigate the functional properties of APB sensitive and insensitive rod pathways. The results revealed several clear-cut differences between the APB sensitive and APB insensitive rod pathways. The latency of Off responses to a flashing spot of light was significantly shorter for the APB insensitive pathways than those for the APB sensitive pathway. Moreover, Off responses of the APB insensitive pathways were found to be capable of following substantially higher stimulus frequencies. Nitric oxide was found to selectively block Off responses in the APB sensitive rod pathway. Collectively, these results provide evidence that the APB sensitive and insensitive rod pathways can convey different types of information signaling light decrements in the dark-adapted retina.     

Macular pigmentation and the spectral sensitivity of retinal ganglion cells of macaques.

Foveal and extrafoveal macaque ganglion cells having spectrally-opponent responses have different spectral sensitivities in the 420–500 nm band. Foveal cells with responses mediated by signals from green-sensitive or blue-sensitive cones, respectively, have a sharper fall-off in sensitivity or a flatter spectral sensitivity at the short wavelengths than extrafoveal cells of the same variety. These differences can be detected in test and field action spectra obtained in the presence of chromatic adaptation and they are dependent on the orientation of the electrical vector of plane-polarized light, indicating that they are not due to neural interactions. The difference spectrum of these action spectra closely resembles the spectral absorbance of the human macular pigment and it is clearly different from the mean spectral sensitivity of rod and blue-sensitive cone signals.