Andreasen A, Danscher G, Juhl S, Stoltenberg M, Revsbech N P, Jensen H, Jensen K B
Department of Neurobiology, Institute of Anatomy, University of Aarhus, Denmark.
J Neurosci Methods. 1997 Mar;72(1):15-21. doi: 10.1016/s0165-0270(96)00149-5.
A mapping at micrometer ranges of the partial oxygen pressure in the rat hippocampus was performed. The oxygen tension in the rat hippocampal region was measured using a glass oxygen microsensor in 30-microm steps along straight lines at a set of stereotactic coordinates. In the hippocampus the pattern of the oxygen tensions reflected the autometallographic zinc sulphide (AMG(ZnS)) pattern, i.e. the pattern of zinc enriched (ZEN) terminals. The highest levels of oxygen tension were recorded in the areas that are most heavily stained with the autometallographic zinc sulphide (AMG(ZnS)) method, like hilus fasciae dentatae. The zinc ions located in synaptic vesicles of the ZEN terminals can also be demonstrated by AMG silver amplification in brains from animals in vivo treated with sodium selenite. This method depends on the presence of a substantial reduction capacity of the tissues as selenite ions (SeO(2)(3)-) must to be reduced to selenide ions (Se2-) before the catalytic zinc selenide crystals can be formed. At some point, either during the transport from the infusion site to the actual target tissue or in the target tissue itself, selenium is reduced from Se(+ IV) to Se(- II). The importance of the reduction capacity of the target tissue in this process is demonstrated by the fact that areas found to have the highest concentration of zinc ions, e.g. hilus fasciae dentatae and the mossy fibres of CA3, are almost unstained after 1 h of i.p. Na2SeO3 exposure. An explanation of this phenomenon could be that the reduction process Se(+ IV) <==> Se(- II) leading to the formation of Se2- is moved to the left by the presence of oxygen, thus inhibiting the precipitation of ZnSe crystals. It is suggested that the subtle oxygen pressure pattern found in the rat hippocampus might also reflect essential biological zinc-related mechanisms vital to brain function.
对大鼠海马体中的局部氧分压进行了微米级范围的映射。在一组立体定向坐标下，使用玻璃氧微传感器沿直线以30微米的步长测量大鼠海马区的氧张力。在海马体中，氧张力模式反映了自动金相硫化锌（AMG(ZnS)）模式，即富含锌（ZEN）的终末模式。在自动金相硫化锌（AMG(ZnS)）方法染色最深的区域，如齿状回门，记录到了最高水平的氧张力。在用亚硒酸钠体内处理的动物大脑中，通过AMG银放大也可以显示位于ZEN终末突触小泡中的锌离子。这种方法依赖于组织具有大量的还原能力，因为在催化形成硒化锌晶体之前，亚硒酸根离子（SeO(2)(3)-）必须还原为硒离子（Se2-）。在某个时刻，无论是在从输注部位运输到实际靶组织的过程中，还是在靶组织本身，硒都从Se(+IV)还原为Se(-II)。靶组织还原能力在这个过程中的重要性通过以下事实得到证明：在腹腔注射亚硒酸钠1小时后，发现锌离子浓度最高的区域，如齿状回门和CA3的苔藓纤维，几乎没有染色。对这种现象的一种解释可能是，导致形成Se2-的Se(+IV)<==>Se(-II)还原过程由于氧的存在而向左移动，从而抑制了ZnSe晶体的沉淀。有人提出，在大鼠海马体中发现的微妙氧压模式也可能反映了对脑功能至关重要的与锌相关的基本生物学机制。
