SPECTRAL AND METABOLIC BASIS OF VISUAL RESPONSES

本申请提出了实验来研究光的过程， 离体脊椎动物暗适应与氧化代谢 光感受器 这些细胞在背景下的电响应， 将使用抽吸微电极获得漂白适应条件。 视觉色素含量的变化将使用 显微分光光度法 分离的细胞的氧化代谢将是 使用微型氧敏电极测量。 心理物理学已经表明，背景和漂白适应是 “等同”。 遵守这一规则主要涉及以下措施： 使用时变刺激的脱敏，这可能是由于非 光感受器响应动力学的等效性。 我们建议比较 视杆细胞和视锥细胞在同等背景水平下的反应动力学， 漂白适应 视杆细胞和视锥细胞外节的内部钙水平[Ca ~（2+）]i与视杆细胞和视锥细胞外节的钙水平有关。 最近被证明可以调节背景适应。 我们建议 研究[Ca 2 +]i是否也是漂白适应的介质。 从漂白适应中恢复需要视觉色素的再生， 但是使用11-顺式锁定的视网膜类似物，我们发现它不 需要形成一种传导视觉色素。 我们建议使用其他 视网膜类似物，以研究恢复是否需要形成一个 视蛋白-发色团席夫碱，或简单地占据发色团 结合位点 光暗条件下视色素水平的维持和恢复 适应需要类维生素A在视网膜和色素之间移动 上皮细胞和可能涉及IRBP（感光细胞间类维生素A结合 蛋白质）。 我们已经能够将类维生素A从IRBP转移到分离的 光感受器（促进暗适应）。 我们建议调查 促进这种转移，特别是视黄醇和 视网膜到光感受器，并研究IRBP的作用， 在光适应过程中类维生素A的转移，即从 光感受器 以前对光感受器的O2消耗的解释是 由于测量不是孤立进行的， 研究单个光感受器细胞的氧消耗， 解决这个问题。 我们将调查O2消耗是否 由光触发，以及它是否由水平变化控制 [Na+]i或[Ca 2 +]i。

This application proposes experiments to study the processes of light and dark adaptation as well as oxidative metabolism in isolated vertebrate photoreceptors. Electrical responses of these cells under background and bleach-adapted conditions will be obtained using suction microelectrodes. Changes in visual pigment content will be measured using microspectrophotometry. Oxidative metabolism of isolated cells will be measured using miniature oxygen-sensitive electrodes. Psychophysics has shown that background and bleaching adaptation are "equivalent". Exceptions to this rule involve principally measures of desensitization using time varying stimuli, that could be due to non- equivalence in photoreceptor response kinetics. We propose to compare response kinetics of rods and cones at equivalent levels of background and bleaching adaptation. The internal calcium level [Ca2+]i in rod and cone outer segments has recently been shown to regulate background adaptation. We propose to investigate whether [Ca2+]i is also a mediator of bleaching adaptation. Recovery from bleaching adaptation requires regeneration of visual pigment, but using 11-cis locked retinal analogs, we have found that it does not require formation of a transducing visual pigment. We proposed using other retinal analogues to investigate whether recovery requires formation of an opsin-chromophore Schiff base, or simply occupation of the chromophore binding site. Maintenance and restoration of visual pigment levels during light and dark adaptation requires movement of retinoid between retina and pigment epithelium and likely involves IRBP (interphotoreceptor retinoid-binding protein). We have been able to transfer retinoid from IRBP to isolated photoreceptors (promoting dark adaptation). We propose to investigate further this transfer, in particular the transfer of both retinol and retinal to photoreceptors, and also to investigate the role of IRBP in the transfer of retinoid during light adaptation, i.e. transfer from photoreceptors. Previous interpretations of the O2 consumption of photoreceptors have been hampered by the measurements not having been made in isolation. Investigation of the O2 consumption of single photoreceptor cells should remove this problem. WE will investigate whether the O2 consumption is triggered by light, and whether it is controlled by changes in the levels of [Na+]i or [Ca2+]i.