Burton B G
Department of Zoology, University of Cambridge, Cambridge, UK.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2002 Aug;188(7):527-38. doi: 10.1007/s00359-002-0327-5. Epub 2002 Jul 5.
The photoreceptors of many animals adapt, when illuminated, by reducing their sensitivities to light and improving their response speeds. Light adaptation is usually considered to be rapid and complete within minutes. However, under bright light conditions, I show that functionally significant improvements in impulse response amplitude and speed continue over the course of an hour in photoreceptors of the fly, Musca domestica. After sustained illumination, the average information rate, a measure of signalling performance, improved by 28% in a sample of sixteen photoreceptors. This long-term light adaptation is a robust phenomenon across animals and is repeatable within the same cell when light-adapting sessions are separated by a period of darkness. White-noise analysis of voltage responses to light and current stimuli indicate that much of the long-term changes observed are attributable to an improvement in the reliability with which photoreceptors register the timing of photon absorptions. It is also found that the impedance amplitude of the photoreceptor increases during long-term adaptation, suggesting that the area of the photoreceptor's membrane is reduced.
许多动物的光感受器在受到光照时会通过降低对光的敏感度并提高反应速度来进行适应。光适应通常被认为在几分钟内迅速且完全。然而，在强光条件下，我发现家蝇的光感受器在一小时的过程中，脉冲反应幅度和速度在功能上有显著改善。持续光照后，在16个光感受器的样本中，作为信号传递性能指标的平均信息率提高了28%。这种长期光适应在动物中是一种稳健的现象，当光适应阶段被一段时间的黑暗隔开时，在同一细胞内是可重复的。对光和电流刺激的电压反应进行白噪声分析表明，观察到的许多长期变化归因于光感受器记录光子吸收时间的可靠性的提高。还发现光感受器的阻抗幅度在长期适应过程中增加，这表明光感受器膜的面积减小。
