Aitken P G, Somjen G G
Brain Res. 1986 Mar 26;369(1-2):163-7. doi: 10.1016/0006-8993(86)90524-x.
To estimate the relative contributions of pre- and postsynaptic elements, and of synaptic and action potential-related currents, to the elevation of interstitial potassium ([K+]o) that occurs during neural activation, we measured [K+]o and focal electrical potential (Vec) during ortho- and antidromic stimulation, before and after blocking synaptic transmission, in the CA1 region of hippocampal tissue slices in vitro. Single stimulus pulses could cause delta [K+]o as large as 0.25 mM in stratum (st.) pyramidale and 0.27 mM in st. radiatum; stimulus trains could cause delta [K+]o as large as 10.5 mM in st. pyramidale and 6.25 mM in st. radiatum. Stimulus trains also caused negative Vec shifts; these shifts were related in a linear fashion to delta [K+]o. For a given increase in [K+]o, the change in Vec was greater in st. radiatum than in st. pyramidale. In st. pyramidale, the delta [K+]o evoked by antidromic stimulation was 65% of the delta [K+]o evoked by orthodromic stimulation (with equal population spike amplitudes). Blockade of synaptic transmission by removal of Ca2+ reduced orthodromically evoked delta [K+]o in st. radiatum by 52%; delta [K+]o in st. pyramidale was abolished. Removal of Ca2+ caused an 11% decrease in the delta [K+]o evoked in st. pyramidale by antidromic stimulation. We conclude that in the layer of dendritic trees (st. radiatum), approximately half of the K+ ions released into the interstitial space during orthodromic stimulation come from presynaptic terminals, with the remainder probably resulting from the ion currents of postsynaptic potentials. Among the pyramidal cell bodies (st. pyramidale), almost all of the excess K+ is released by action potential currents.
为了评估突触前和突触后成分以及与突触和动作电位相关的电流对神经激活期间细胞外间隙钾离子浓度（[K⁺]o）升高的相对贡献，我们在体外海马组织切片的CA1区，于阻断突触传递前后，分别在正向和逆向刺激期间测量了[K⁺]o和局部电位（Vec）。单个刺激脉冲可在锥体层（st. pyramidale）引起高达0.25 mM的[K⁺]o变化，在辐射层（st. radiatum）引起高达0.27 mM的变化；刺激串可在锥体层引起高达10.5 mM的[K⁺]o变化，在辐射层引起高达6.25 mM的变化。刺激串还会引起Vec负向偏移；这些偏移与[K⁺]o变化呈线性关系。对于给定的[K⁺]o升高，辐射层的Vec变化大于锥体层。在锥体层，逆向刺激诱发的[K⁺]o变化是正向刺激诱发的[K⁺]o变化的65%（群体峰电位幅度相等）。通过去除Ca²⁺阻断突触传递，可使辐射层正向刺激诱发的[K⁺]o变化降低52%；锥体层的[K⁺]o变化则完全消失。去除Ca²⁺使逆向刺激在锥体层诱发的[K⁺]o变化降低了11%。我们得出结论，在树突树层（辐射层），正向刺激期间释放到细胞外间隙的K⁺离子中，约一半来自突触前终末，其余可能来自突触后电位的离子电流。在锥体细胞体层（锥体层），几乎所有多余的K⁺都是由动作电位电流释放的。
