The time course of light adaptation in vertebrate retinal rods.
The time course of light adaptation in vertebrate retinal rods.
复制标题
脊椎动物视网膜杆的光适应时间过程。
DOI：
10.1007/978-1-4615-0121-3_3
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发表时间：
2002
影响因子：
--
通讯作者：
Makino,ClintL
中科院分区：
文献类型：
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作者：
Calvert,PeterD;Makino,ClintL
在稳定的光照下，视杆的光响应随着时间的推移而减弱，因为光失去了产生响应的效力。这种脱敏是自适应的，因为它扩展了环境光水平的范围，在该范围内，视杆信号的光强度变化了几个数量级。适应开始迅速展开后，光的时间常数为-1秒，导致杆的稳定光的敏感性下降了近两个对数单位。此后，一个缓慢得多的适应阶段以9秒的时间常数演变。在此阶段，杆的灵敏度降低了一个额外的对数单位。这两个阶段都依赖于光诱导的细胞内Ca 2+的下降。光适应的快速阶段可以归因于Ca 2+反馈过程调节光敏视紫红质的寿命、cGMP合成和cGMP门控通道对cGMP的敏感性。虽然慢相的机制尚不清楚，但似乎包括进一步调节光活化视紫红质的寿命。
The photoresponse of a rod wanes over time in steady illumination, as light loses its efficacy in generating the response. Such desensitization is adaptive because it extends the range of ambient light levels over which the rod signals changes in light intensity by several orders of magnitude. Adaptation begins to unfold rapidly after the onset of light with a time constant of —1 s, causing the rod’s sensitivity to steady light to decrease by nearly two log units. Thereafter, a much slower phase of adaptation evolves with a time constant of 9 s. During this phase the rod’s sensitivity decreases by an additional log unit. Both phases are dependent upon the light-induced fall in intracellular Ca2+. The fast phase of light adaptation can be attributed to Ca2+feedback processes regulating the lifetime of photoactivated rhodopsin, cGMP synthesis and sensitivity of the cGMP-gated channel to cGMP. Although the mechanism(s) of the slow phase is not yet known, it appears to include further regulation of the lifetime of photoactivated rhodopsin.