Ionic current model for the inner-segment of a retinal photoreceptor
Ionic current model for the inner-segment of a retinal photoreceptor
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视网膜感光器内段的离子电流模型
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
S. Usui
中科院分区：
文献类型：
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作者：
T. Ogura;Y. Kamiyama;S. Usui
从形态学的角度来看，视网膜感光器由外节、内节和突触组成。每一个都有自己的功能作用。外节接受光刺激并将其转化为光敏电流。内段通过该电流变化与内段中存在的各种离子电流之间的相互作用形成光响应。突触根据光响应调节信息传递物质的释放，并将信息传递到双极细胞和水平细胞。虽然已经有许多关于这些感光器功能的生理学研究，但是必须构建模型并对该模型进行模拟分析，以便澄清感光器的各种离子电流在光响应中的行为以及它们的作用等信息处理功能的细节。从这个角度出发，本文基于光感受器内节膜电位依赖性电流的生理学知识，构建了一个离子电流模型。然后，钙依赖性电流被认为是和行为的离子电流对应的细胞中的钙离子密度的变化进行建模，考虑到细胞内机制的钙离子。结果表明，该模型在光感受器内节的膜电位和膜电流响应方面表现出相同的行为。通过模拟确定了Ca 2+峰期各离子电流的时程，这是生理实验难以测量的。其结果是，每个离子电流上的Ca 2+尖峰的修改效果指示。基于离子电流的动态行为，还考虑了膜电位依赖性K+电流阻断期和对照状态之间的尖峰波形的差异。分析了细胞内Ca 2+浓度变化对膜电位响应的影响，结果表明，随着细胞内Ca 2+浓度的增加，Ca 2+依赖性Cl−电流的激活对Ca 2+峰电位的终止有很大影响。作者认为，本文提出的光感受器内节模型将有助于从生理工程的角度分析视网膜功能的未来研究。© 1998 Scripta Technica. Syst Comp Jpn，28（13）：55-66，1997
From the morphological point of view, the retinal photoreceptor is composed of the outer segment, the inner segment, and the synapse. Each of these has its own functional role. The outer segment receives light stimulation and changes it into the photosensitive current. The inner segment forms the photoresponse through the interaction between that current change and the various ionic currents existing in the inner segment. The synapse adjusts the release of the information transmission substance according to the photoresponse, and transmits the information to the bipolar cell and the horizontal cell. Although there have been many physiological studies concerning these photoreceptor functions, a model must be constructed and a simulation analysis must be applied to that model in order to clarify such details of the information processing function as the behavior of the various ionic currents of the photoreceptor in the photoresponse, as well as their roles. From such a viewpoint, this paper constructs a model for the ionic currents based on physiological knowledge of the membrane potential-dependent current existing in the inner segment of the photoreceptor. Then, a Ca2+-dependent current is considered and the behavior of the ionic current corresponding to the change of Ca2+ density in the cell is modeled, considering the intracell mechanism for Ca2+. It is verified that the model exhibits the same behavior in terms of the membrane potential and the membrane current response of the inner segment of the photoreceptor. The time-course of each ionic current in the Ca2+ spike period is determined by simulation, which has been difficult to measure by physiological experiments. As a result, the modification effect of each ionic current on the Ca2+ spike is indicated. The difference of the spike waveform between the membrane potential-dependent K+-current blocking period and the control state is also accounted for, based on the dynamic behavior of the ionic currents. The effect of the intracellular Ca2+ density change on the membrane potential response is analyzed, and it is shown that the termination of the Ca2+ spike is greatly affected by the activation of the Ca2+ dependent Cl− current accompanying the intracellular Ca2+ density increase. The authors believe that the model for the inner segment of the photoreceptor presented in this paper will contribute greatly to future studies of the retinal function through analysis from a physiological engineering point of view. © 1998 Scripta Technica. Syst Comp Jpn, 28(13): 55–66, 1997