Perlman I, Normann R A, Chandler J P, Lipetz L E
Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel.
Vis Neurosci. 1990 Jan;4(1):53-62. doi: 10.1017/s0952523800002765.
A technique by which the retina can be isolated from the turtle eye is described. Scanning electron microscopy revealed morphological variability between preparations and also between regions of the same one. Large areas were often totally free of any pigment epithelial cells, yet contained a high proportion of photoreceptors with complete outer segments. However, adjacent regions may contain photoreceptors without outer segments or with fragmented ones. The physiological properties of the horizontal cells also demonstrated large variability between different preparations. In all cases, lowering calcium concentration from 2 mM to 0.1-0.5 mM depolarized the horizontal cells and augmented the amplitude of the maximum photoresponses. However, these effects were accompanied by changes in the photoresponse kinetics and by a reduction in the horizontal cell sensitivity to light. Moreover, prolonged exposure to low calcium induced permanent damage to the retina as was indicated by the reduction in the response amplitude after superfusion with 2 mM calcium solution had been resumed. The toxic effects of low calcium were most apparent when superfusion with 0.1-1.0 microM calcium concentration was performed. These solutions induced complex time-dependent effects on the resting potential of horizontal cells and on the amplitude and kinetics of the photoresponses. We conclude from these observations that the normal concentration of extracellular calcium in the turtle retina is in the 2 mM range.
本文描述了一种从龟眼中分离视网膜的技术。扫描电子显微镜显示，不同制备物之间以及同一制备物的不同区域之间存在形态学差异。大片区域通常完全没有任何色素上皮细胞，但含有高比例的具有完整外段的光感受器。然而，相邻区域可能含有没有外段或外段破碎的光感受器。水平细胞的生理特性在不同制备物之间也表现出很大差异。在所有情况下，将钙浓度从2 mM降至0.1 - 0.5 mM会使水平细胞去极化，并增加最大光反应的幅度。然而，这些效应伴随着光反应动力学的变化以及水平细胞对光的敏感性降低。此外，长时间暴露于低钙环境会导致视网膜永久性损伤，这表现为恢复用2 mM钙溶液灌流后反应幅度降低。当用0.1 - 1.0 microM钙浓度进行灌流时，低钙的毒性作用最为明显。这些溶液对水平细胞的静息电位以及光反应的幅度和动力学产生复杂的时间依赖性影响。我们从这些观察结果得出结论，龟视网膜中细胞外钙的正常浓度在2 mM范围内。
