McRipley M A, Ahmed J, Chen E P, Linsenmeier R A
Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208-3107, USA.
Vis Neurosci. 1997 Mar-Apr;14(2):339-50. doi: 10.1017/s0952523800011469.
Acute hypoxemia (low PaO2) leads to changes in oxygen consumption and electrical responses of the outer retina of cats, but inner retinal ERG components and ganglion cell responses have been shown to be quite resistant to hypoxemia. The purpose of this study was to determine whether the resistance of the inner retina depends on (1) the stimulus conditions, specifically the degree of light adaptation; and (2) the ability of the photoreceptors to increase glycolysis during hypoxemia. To address these issues, recordings of single ganglion cell action potentials and of the b-wave and scotopic threshold response (STR) of the electroretinogram (ERG) were made from the eyes of anesthetized cats during hypoxemia alone and hypoxemia plus hypoglycemia. Ganglion cells appeared to be equally resistant to hypoxemia at high and low backgrounds (3.3 to 9.7 log equivalent quanta(555 nm)-deg-2(-s)-1), and the STR, recorded with dim stimuli during dark adaptation, when photoreceptor oxygen consumption is most susceptible to hypoxemia, was unchanged until PaO2 was below 30 mm Hg. The amplitude of the b-wave was similarly resistant to hypoxemia when the animal was normoglycemic. During hypoglycemia, however, both the b-wave and the STR became more sensitive to hypoxemia, beginning to change at PaO2s as high as 50 mm Hg when blood glucose was 40-50 mg/dl. It is argued that hypoglycemia limits or prevents the increased glycolytic ATP production that would ordinarily occur when the photoreceptor oxygen supply decreases, and that increased photoreceptor glycolysis is essential in the protection of the retina against mild hypoxemia.
急性低氧血症（低动脉血氧分压）会导致猫的氧气消耗和视网膜外层电反应发生变化，但已证明视网膜内层的视网膜电图（ERG）成分和神经节细胞反应对低氧血症具有相当的抗性。本研究的目的是确定视网膜内层的抗性是否取决于：（1）刺激条件，特别是光适应程度；以及（2）光感受器在低氧血症期间增加糖酵解的能力。为了解决这些问题，在单独低氧血症以及低氧血症加低血糖症期间，从麻醉猫的眼睛记录单个神经节细胞动作电位以及ERG的b波和暗视阈值反应（STR）。在高背景和低背景（3.3至9.7对数等效量子（555纳米）-度-2（-秒）-1）下，神经节细胞对低氧血症的抗性似乎相同，并且在暗适应期间用弱刺激记录的STR，在光感受器氧气消耗对低氧血症最敏感时，直到动脉血氧分压低于30毫米汞柱时才会发生变化。当动物血糖正常时，b波的振幅对低氧血症同样具有抗性。然而，在低血糖期间，b波和STR对低氧血症变得更加敏感，当血糖为40 - 50毫克/分升时，在动脉血氧分压高达50毫米汞柱时就开始发生变化。有人认为，低血糖会限制或阻止通常在光感受器氧气供应减少时发生的糖酵解ATP生成增加，并且增加的光感受器糖酵解对于保护视网膜免受轻度低氧血症至关重要。
