The absence of spread of adaptation between rod photoreceptors in turtle retina.
The absence of spread of adaptation between rod photoreceptors in turtle retina.
复制标题
乌龟视网膜中杆状光感受器之间缺乏适应传播。
DOI：
10.1113/jphysiol.1985.sp015894
复制
发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Green,DG
中科院分区：
文献类型：
--
作者：
Copenhagen,DR;Green,DG
研究了鳄龟视网膜弱背景适应和视杆间脱敏的空间扩散。细胞内膜电位记录从这些光感受器在眼杯制备。视杆细胞反应的动力学和灵敏度被大的、非常暗淡的背景显著改变。对于暗适应闪光灵敏度SDF大于1.0 mV/Rh* 的25个最敏感的杆，Rh* 是每个杆的有效光异构化的数量，将线性范围响应的幅度减半所需的背景强度平均为0.21 Rh* s-1。这些暗淡的背景使测试响应的达峰时间减少了50%。测量了不同强度的全场背景对大测试点响应的脱敏效应。增量闪光灵敏度SF对背景强度IB的依赖关系符合以下形式（公式：见正文），其中I 0是使SDF减半的背景强度。同样的强度依赖性也适用于狭缝形背景场，这种背景场使对小测试点的反应不敏感。大的、非常暗的闪光和连续的背景的脱敏效果需要几秒钟才能出现并衰减到黑暗的水平。这与光子的稀疏性相结合表明，来自单个光异构化的脱敏可以持续几秒钟。斑点和环形背景的脱敏效果的比较表明，小斑点背景叠加在中心测试点脱敏棒更有效地比环形字段。即使当环形图案在视杆中产生更大的维持超极化时，这一发现也是正确的。因此，脱敏与背景场诱发的稳定维持的超极化之间没有独特的关系。通过将狭缝形背景场放置在杆感受野的不同位置，确定适应对与穿刺杆距离的依赖性。位移狭缝刺激的脱敏效果被发现下降更迅速地与距离比激励。将狭缝从中心移位20微米，使其减敏效果减少1个对数单位以上。相比之下，在相同的距离（λ范围从50到70微米）激发下降到约80%。减敏随距离的下降与计算出的光从狭缝散射的随距离的下降相匹配。在同等脱敏、叠加和位移狭缝的存在下，测试响应的动力学没有差异。（400字处截断摘要）
Adaptation by weak backgrounds and the spatial spread of desensitization between rods was studied in the snapping turtle retina, Chelydra serpentina. Intracellular membrane potentials were recorded from these photoreceptors in an eyecup preparation. The kinetics and sensitivity of rod responses were changed significantly by large, very dim backgrounds. For the twenty‐five most sensitive rods where the dark‐adapted flash sensitivity, SDF, was greater than 1.0 mV/Rh*, Rh* being the number of effective photo‐isomerizations per rod, the background intensity required to halve the amplitude of the linear range response averaged 0.21 Rh* s‐1. The time‐to‐peak of the test responses was reduced up to 50% by these dim backgrounds. The desensitizing effects of full field backgrounds of various intensities on the responses to large test spots were measured. The dependence of incremental flash sensitivity, SF, on background intensity, IB, followed the form (FORMULA: SEE TEXT) where I0 is the background intensity which halved SDF. The same intensity dependence held for slit‐shaped background fields that desensitized responses to small test spots. The desensitizing effects of large, very dim flashed and continuous backgrounds took several seconds to appear and decay to dark levels. This in conjunction with the sparsity of photons suggests, that the desensitization from a single photoisomerization can persist for several seconds. A comparison of the desensitizing effects of spot and annular backgrounds revealed that small spot backgrounds superimposed on the centered test spots desensitized rods more effectively than annular fields. This finding held true even when annular patterns produced a greater maintained hyperpolarization in the rods. Thus, there was no unique relationship between desensitization and the steady maintained hyperpolarization evoked by a background field. The dependence of adaptation on distance from the impaled rod was determined with slit‐shaped background fields placed at different positions across the rod's receptive field. The desensitizing effect of displaced slit stimuli was found to decline much more rapidly with distance than excitation. Displacing the slit by 20 micron from the centre reduced its desensitizing effect by more than 1 log unit. In contrast, excitation fell to about 80% at the same distance (lambda ranging from 50 to 70 micron). The fall off of desensitization with distance matched the calculated fall off with distance of light scatter from a slit. No difference was noted in the kinetics of test responses in the presence of equally desensitizing, superimposed and displaced slits.(ABSTRACT TRUNCATED AT 400 WORDS)