Gresh Jeffrey, Goletz Patrice W, Crouch Rosalie K, Rohrer Baerbel
Department of Ophthalmology, Medical University of South Carolina, Charleston 29425, USA.
Vis Neurosci. 2003 Mar-Apr;20(2):211-20. doi: 10.1017/s0952523803202108.
To determine whether the photoreceptors change structurally and functionally during aging, and to analyze whether pigmentation in the retinal pigment epithelium might be a contributing factor. Young, adult, and aged C57BL/6 and Balb/c mice (1, 4, and 17 months of age) were housed under a 12-h light/12-h dark cycle, with an ambient light intensity at the eye level of the mice of 85 +/- 18 lux. Scotopic single-flash and photopic-flicker electroretinograms (ERGs) after complete dark adaptation were used to assess rod and cone function, respectively. Numbers of rod photoreceptors were counted in plastic sections, and rhodopsin levels were measured using absorption difference spectrophotometry. Numbers and types of cones were determined using lectin staining in retinal flatmounts and cone-specific antibodies in radial frozen sections. Young pigmented C57BL/6 and nonpigmented Balb/c mice had similar numbers of rods. In both mouse strains, there was an overall decline in rod photoreceptor number during aging, which was more pronounced in albino mice. Rod cell numbers correlated with a drop in the overall amount of rhodopsin and a reduction in the maximum a-wave of the rod ERG. The number of short-wavelength cones was unaffected by age and pigmentation, whereas an age-related decline was observed in mid-wavelength (MWL) cones in albino, but not in pigmented mice. In contrast, MWL cone function was reduced during aging in both strains. Flicker-fusion frequency was determined to be approximately 10 Hz lower in albino animals, which is due to prolonged b-waves in these ERGs. Age-related changes were found in both photoreceptor systems, rods and cones, and in both pigmented and nonpigmented mice. However, rod photoreceptors appear to be more susceptible to both aging and the lack of pigmentation, when compared to cones. These results may help as we begin to understand certain age-related retinal diseases.
为了确定光感受器在衰老过程中是否发生结构和功能变化，并分析视网膜色素上皮中的色素沉着是否可能是一个促成因素。将年轻、成年和老年的C57BL/6和Balb/c小鼠（1、4和17月龄）饲养在12小时光照/12小时黑暗周期下，小鼠眼部水平的环境光照强度为85±18勒克斯。完全暗适应后的暗视单闪光和明视闪烁视网膜电图（ERG）分别用于评估视杆和视锥功能。在塑料切片中对视杆光感受器的数量进行计数，并使用吸收差分光光度法测量视紫红质水平。使用视网膜铺片中的凝集素染色和放射状冰冻切片中的视锥特异性抗体来确定视锥的数量和类型。年轻的有色C57BL/6小鼠和无色Balb/c小鼠的视杆数量相似。在这两种小鼠品系中，衰老过程中视杆光感受器数量总体下降，在白化小鼠中更为明显。视杆细胞数量与视紫红质总量的下降以及视杆ERG最大a波的降低相关。短波长视锥的数量不受年龄和色素沉着的影响，而在白化小鼠中，中波长（MWL）视锥出现与年龄相关的减少，而在有色小鼠中则未观察到。相反，在这两种品系中，衰老过程中MWL视锥功能均降低。白化动物的闪光融合频率被确定比正常动物低约10 Hz，这是由于这些ERG中的b波延长所致。在视杆和视锥这两种光感受器系统以及有色和无色小鼠中均发现了与年龄相关的变化。然而，与视锥相比，视杆光感受器似乎对衰老和色素缺乏更敏感。这些结果可能有助于我们开始理解某些与年龄相关的视网膜疾病。
