Circadian modulation of temporal properties of the rod pathway in larval Xenopus.
Circadian modulation of temporal properties of the rod pathway in larval Xenopus.
复制标题
非洲爪蟾幼虫视杆通路时间特性的昼夜节律调节。
DOI：
10.1152/jn.00344.2004
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发表时间：
2004
影响因子：
2.5
通讯作者：
Barlow,RobertB
中科院分区：
文献类型：
--
作者：
Solessio,Eduardo;Scheraga,David;Engbretson,GustavA;Knox,BarryE;Barlow,RobertB
生物钟是视觉系统的组成部分。它们帮助调整动物的视力以适应环境光照的昼夜变化。要了解如何昼夜节律钟可能会适应视觉灵敏度，我们调查的空间和时间特性的视动反应的非洲爪蟾laevistadpoles（Nieuwkoop和费伯，发展阶段48）使用修改后的2-替代优先观看的方法。我们将动物保持在恒定的黑暗中，并在其主观的白天和黑夜中测量时间敏感性。我们发现，他们的行为反应可以解释在2个机制具有不同的时间属性。更敏感的机制在低时间频率和中间波长（λmax= 520 nm）下工作，这些特性与杆信号一致。这种机制的阈值约为0.04光异构化棒-1s-1，与单光子探测一致。一个不太敏感的机制响应较高的时间频率（截止= 12 Hz），并具有广泛的光谱灵敏度（370-720 nm），与多种类别的锥信号一致。这种锥机制没有改变，但更敏感的杆机制的截止频率从夜间的0.35 Hz变为主观白天的1.1 Hz，从而增强了动物对暗淡快速变化的刺激的敏感性。视杆细胞时间截止频率的昼夜变化在完全黑暗中循环，是内源性昼夜节律的特征。的行为测量杆机制的时间特性密切对应的电生理测量的视网膜反应，表明杆信号调制的水平外视网膜。
Circadian clocks are integral components of visual systems. They help adjust an animal's vision to diurnal changes in ambient illumination. To understand how circadian clocks may adapt visual sensitivity, we investigated the spatial and temporal properties of optomotor responses of youngXenopus laevistadpoles (Nieuwkoop and Faber, developmental stage 48) using a modified 2-alternative preferential-viewing method. We maintained animals in constant darkness and measured temporal sensitivity during their subjective day and night. We found that their behavioral responses can be explained in terms of 2 mechanisms with different temporal properties. The more sensitive mechanism operates at low temporal frequencies and intermediate wavelengths (λmax= 520 nm), properties consistent with rod signals. Threshold for this mechanism is approximately 0.04 photoisomerizations rod−1s−1, consistent with single-photon detection. A less-sensitive mechanism responds to higher temporal frequencies (cutoff = 12 Hz) and has broad spectral sensitivity (370–720 nm), consistent with multiple classes of cone signals. This cone mechanism does not change, but the cutoff frequency of the more sensitive rod mechanism shifts from 0.35 Hz at night to 1.1 Hz during the subjective day, thereby enhancing the animal's sensitivity to dim rapidly changing stimuli. This day–night shift in rod temporal cutoff frequency cycles in complete darkness, characteristic of an endogenous circadian rhythm. The temporal properties of the behaviorally measured rod mechanism correspond closely with those of the electrophysiologically measured retinal response, indicating that the rod signals are modulated at the level of the outer retina.