感光神经节细胞的活体形态特点:异于视杆、视锥细胞的光感受器

摘要

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.%目的 在细胞水平研究活体感光视网膜神经节细胞(ipRGCs)形态特点,其在弯曲视网膜组织内与视杆、视锥细胞的位置关系,及其光感受器光反应信号特点.方法 研究263个经增强型绿色荧光蛋白(EGFP)标记的活体ipRGCs,经用膜片钳记录技术复染,通过数码录像记录每个细胞从神经纤维层到内核层形态,分析其细胞体和树突在视网膜内丛状层、神经节细胞层的分布特点,及与弯曲的视网膜几何结构的匹配.对ipRGCs与视杆、视锥细胞光感受器的几何位置关系进行重建分析,推测ipRGCs系统的视功能. 结果 ipRGCs树突依视网膜曲度在内丛状层呈严格的3个亚层分布,亚层之间无感光树突面存在.每一亚层被稀疏的ipRGCs树突网络全覆盖成感光曲面,但对于每个ipRGCs,其树突在这些特定视网膜内丛状亚层曲面呈随机分布.所有ipRGCs树突形成的全视网膜感光三曲面与视杆、视锥细胞呈正交排列.ipRGCs树突形成的感光曲面与内丛状层的ON/OFF功能分层不一致,黑视色素及内在钙钠动作电位离子通道表达水平在单个M1、M2、M3细胞呈随机性.M4、M5细胞形态和功能与传统神经节细胞交叉. 结论 ipRGCs树突形成的多层全视网膜感光曲面与视杆、视锥细胞在弯曲的视网膜三维空间呈正交排列,单个ipRGCs形态、黑视色素及内在钙钠动作电位离子通道表达水平的随机性都提示其具有与视杆、视锥细胞不同的光感受器特点.