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首页> 外文期刊>Comparative biochemistry and physiology, Part A. Molecular and integrative physiology >Ecophysiology of neuronal metabolism in transiently oxygen-depleted environments: Evidence that GABA is accumulated pre-synaptically in the cerebellum
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Ecophysiology of neuronal metabolism in transiently oxygen-depleted environments: Evidence that GABA is accumulated pre-synaptically in the cerebellum

机译：短暂耗氧环境中神经元代谢的生态生理学：GABA在小脑中先突触累积的证据

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Interactions between coral reef topography, tide cycles, and photoperiod provided selection pressure for adaptive physiological changes in sheltered hypoxic niches to be exploited by specialized tropical reef fish. The epaulette shark Hemiscyllium ocellatum withstands cyclic hypoxia in its natural environment, many hours of experimental hypoxia, and anoxia for up to 5h. It shows neuronal hypometabolism in response to 5% oxygen saturation. Northern-hemisphere hypoxia- and anoxia-tolerant vertebrates that over-winter under ice alter their inhibitory to excitatory neurotransmitter balance to forestall brain ATP depletion in the absence of oxidative phosphorylation. GABA immunochemistry, HPLC analysis and receptor binding studies in H. ocellatum cerebellum revealed a heterogeneous regional accumulation of neuronal GABA despite no change in its overall concentration, and a significant increase in GABAA receptor density without altered binding affinity. Increased GABAA receptor density would protect the cerebellum during reoxygenation when transmitter release resumes. While all hypoxia- and anoxia-tolerant teleosts examined to date respond to low oxygen levels by elevating brain GABA, the phylogenetically older epaulette shark did not, suggesting that it uses an alternative neuroprotective mechanism for energy conservation. This may reflect an inherent phylogenetic difference, or represent a novel ecophysiological adaptation to cyclic variations in the availability of oxygen.
机译：珊瑚礁地形，潮汐周期和光周期之间的相互作用为有遮盖性的低氧生态位适应性生理变化提供了选择压力，这些生态位将被专门的热带礁鱼开发。肩章鲨鱼半球藻在其自然环境中承受周期性的缺氧，数小时的实验性缺氧以及长达5小时的缺氧。它显示了对5％氧饱和度的神经元低代谢。在冰下过冬的北半球耐缺氧和耐缺氧的脊椎动物改变了它们对兴奋性神经递质平衡的抑制作用，从而在没有氧化磷酸化的情况下阻止了大脑的ATP消耗。 G. ocellatum小脑中的GABA免疫化学，HPLC分析和受体结合研究显示，尽管总浓度没有变化，神经元GABA仍存在异质区域积累，并且GABAA受体密度显着增加而结合亲和力却没有改变。当变送器恢复释放时，增加的GABAA受体密度将在复氧期间保护小脑。尽管迄今为止检查的所有耐缺氧和耐缺氧的硬骨鱼都能通过升高大脑GABA来应对低氧水平，但系统发育较老的肩章鲨鱼却没有，这表明它使用了另一种神经保护机制来进行节能。这可能反映了内在的系统发育差异，或代表了对氧可利用性的周期性变化的新的生态生理适应。

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