Rod Photoreceptors Avoid Saturation in Bright Light by the Movement of the G Protein Transducin
Rod Photoreceptors Avoid Saturation in Bright Light by the Movement of the G Protein Transducin
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DOI：
10.1523/jneurosci.2817-20.2021
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发表时间：
2021-04-14
影响因子：
5.3
通讯作者：
Sampath, Alapakkam P.
中科院分区：
文献类型：
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作者：
Frederiksen, Rikard;Morshedian, Ala;Sampath, Alapakkam P.
视杆细胞感光器可以通过暴露于明亮的背景光而饱和，使得叠加在背景上的闪光不能引起可检测的响应。这种现象被称为增量饱和，最早由阿吉拉尔和斯泰尔斯从心理学角度证明，此后许多研究表明，这种现象发生在单杆细胞中。然而，最近的实验表明，在某些光照条件下，视杆细胞可能能够避免饱和。现在，我们在离体视网膜电图和单细胞记录中显示，即使在非常明亮的光线下连续和长时间暴露，雄性和雌性小鼠的视杆细胞也能恢复多达15%的暗电流，并且这种反应可以持续数小时。在平行恢复外段电流是一个;10倍增加杆光响应的灵敏度。在转基因小鼠中，G蛋白转导素的光依赖性易位减少，这种恢复降低。外节transducin的减少与视杆内的视觉色素再生的新机制一起使视杆能够在整个视觉生理范围内保持反应。以这种方式，杆能够避免转导通道关闭的延长时间，这是已知的导致感光细胞变性。
Rod photoreceptors can be saturated by exposure to bright background light, so that no flash superimposed on the background can elicit a detectable response. This phenomenon, called increment saturation, was first demonstrated psychophysically by Aguilar and Stiles and has since been shown in many studies to occur in single rods. Recent experiments indicate, however, that rods may be able to avoid saturation under some conditions of illumination. We now show in ex vivo electroretinogram and single-cell recordings that in continuous and prolonged exposure even to very bright light, the rods of mice from both sexes recover as much as 15% of their dark current and that responses can persist for hours. In parallel to recovery of outer segment current is an ;10-fold increase in the sensitivity of rod photoresponses. This recovery is decreased in transgenic mice with reduced light-dependent translocation of the G protein transducin. The reduction in outer-segment transducin together with a novel mechanism of visual-pigment regeneration within the rod itself enable rods to remain responsive over the whole of the physiological range of vision. In this way, rods are able to avoid an extended period of transduction channel closure, which is known to cause photoreceptor degeneration.