Effect of anoxia on the electroretinogram of three anoxia-tolerant vertebrates

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2008-08, Vol.150 (4), p.395-403
• Main Authors: Stensløkken, Kåre-Olav, Milton, Sarah L., Lutz, Peter L., Sundin, Lena, Renshaw, Gillian M.C., Stecyk, Jonathan A.W., Nilsson, Göran E.
• Format: Article
• Language: English
• Subjects: Adenosine; Adenosine - metabolism; Adenosine Triphosphate - metabolism; Animals; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; Brackish; Carassius carassius; Carps; crucian carp; Electroretinography - methods; epaulette shark; ERG; evoked-potentials; Freshwater; Fysiologi; Hemiscyllium ocellatum; Hypoxia; intracellular responses; Marine; Microbiology; Mikrobiologi; Models, Statistical; Neurons - metabolism; Oxygen - metabolism; perfused eye; phosphodiesterase inhibitors; Physiology; pigment epithelium; Rana pipiens; Ranidae; Retina - metabolism; retinal ischemia; shark hemiscyllium-ocellatum; Sharks; Species Specificity; Trachemys scripta; turtle brain; Turtles; Vertebrates
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2008.03.022

To survive anoxia, neural ATP levels have to be defended. Reducing electrical activity, which accounts for 50% or more of neural energy consumption, should be beneficial for anoxic survival. The retina is a hypoxia sensitive part of the central nervous system. Here, we quantify the in vivo retinal light response (electroretinogram; ERG) in three vertebrates that exhibit varying degrees of anoxia tolerance: freshwater turtle ( Trachemys scripta), epaulette shark ( Hemiscyllium ocellatum) and leopard frog ( Rana pipiens). A virtually total suppression of ERG in anoxia, probably resulting in functional blindness, has previously been seen in the extremely anoxia-tolerant crucian carp ( Carassius carassius). Surprisingly, the equally anoxia-tolerant turtle, which strongly depresses brain and whole-body metabolism during anoxia, exhibited a relatively modest anoxic reduction in ERG: the combined amplitude of turtle ERG waves was reduced by ~ 50% after 2 h. In contrast, the shark b-wave amplitude practically disappeared after 30 min of severe hypoxia, and the frog b-wave was decreased by ~ 75% after 40 min in anoxia. The specific A 1 adenosine receptor antagonist CPT significantly delayed the suppression of turtle ERG, while the hypoxic shark ERG was unaffected by the non-specific adenosine receptor antagonist aminophylline, suggesting adenosinergic involvement in turtle but not in shark.