Matthews H R
Physiological Laboratory, University of Cambridge, UK.
J Physiol Paris. 1992;86(1-3):147-55. doi: 10.1016/s0928-4257(05)80020-8.
The process of light adaptation in vertebrate rod and cone photoreceptors is believed to involve a diffusible cytoplasmic messenger. Two lines of evidence indicate that photoreceptor light adaptation is mediated by a light-induced fall in cytoplasmic calcium concentration (Ca2+i). First, if changes in calcium concentration are slowed by the incorporation of calcium chelators into the photoreceptor cytoplasm then light adaptation is slowed also. Second, if the normal control of Ca2+i is prevented by simultaneously minimising calcium influx and efflux across the outer segment membrane by means of external solution changes, then all of the manifestations of light adaptation are abolished. Furthermore, recent results show that changes in Ca2+i imposed in the absence of light are sufficient to cause at least some of the manifestations of light adaptation. Together these results indicate that calcium acts as the messenger of light adaptation in the photoreceptors of both lower and higher vertebrates.
脊椎动物视杆和视锥光感受器的光适应过程被认为涉及一种可扩散的细胞质信使。有两条证据表明，光感受器的光适应是由光诱导的细胞质钙浓度（Ca2+i）下降介导的。首先，如果通过将钙螯合剂引入光感受器细胞质来减缓钙浓度的变化，那么光适应也会减缓。其次，如果通过外部溶液变化同时最小化跨外段膜的钙流入和流出，从而阻止对Ca2+i的正常控制，那么光适应的所有表现都会被消除。此外，最近的结果表明，在无光情况下施加的Ca2+i变化足以引起至少一些光适应的表现。这些结果共同表明，钙在低等和高等脊椎动物的光感受器中都充当光适应的信使。
