DISTRIBUTION OF ELECTROTONIC SYNAPSES ON IDENTIFIED LAMPREY NEURONS - A COMPARISON OF A MODEL PREDICTION WITH AN ELECTRON-MICROSCOPIC ANALYSIS
DISTRIBUTION OF ELECTROTONIC SYNAPSES ON IDENTIFIED LAMPREY NEURONS - A COMPARISON OF A MODEL PREDICTION WITH AN ELECTRON-MICROSCOPIC ANALYSIS
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DOI：
10.1152/jn.1983.49.3.705
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发表时间：
1983-01-01
影响因子：
2.5
通讯作者：
CHRISTENSEN, BN
中科院分区：
文献类型：
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作者：
CHRISTENSEN, BN
单突触兴奋性突触后电位(EPSP)的细胞内记录是在刺激单个突触前巨大轴突后，从七鳃鳗脊髓中的一个已鉴定的巨型中间神经元获得的。EPSP既有电渗性成分，又有化学成分。用辣根过氧化物酶(HRP)标记巨型中间神经元，有时还标记巨型轴突。用光镜和电子显微镜相结合的方法，对7个中间神经元HRP标记的树突状突起上轴突形成的缝隙连接进行了鉴定，并根据细胞的踪迹在树突图上标记了它们的位置。一个巨大的中间神经元上的缝隙连接总数从最少的9个到最多的23个不等。树枝上的缝隙连接数量从1到9不等。对于所有7个神经元，最接近的缝隙连接位于.apprx。距离索马岛65微米，离索马岛最远280微米。当缝隙连接位置被绘制为离胞体的电紧张性距离的函数时，其分布的变异性显著减小。突触位置平均为.apprx。0.5个空间常数，这个值与通过分析这些神经元的电紧张性突触电位的半宽度和上升时间所得的值相比较是有利的。结果表明，平均而言，突触前轴突倾向于在与胞体相同的电距离处进行突触接触。
Intracellular recordings of the monosynaptic excitatory postsynaptic potential (EPSP) were made from an identified giant interneuron in the lamprey spinal cord following stimulation of a single identified presynaptic giant axon. The EPSP had both electrotonic and chemical components. The giant interneuron and sometimes the giant axon were labeled with horseradish peroxidase (HRP). Using combined light and electron microscopy (EM), gap junctions formed by the axon on the HRP-labeled dendritic trees of 7 interneurons were identified and their position marked on dendritic diagrams made from tracings of the cells. The total number of gap junctions on a giant interneuron varied from a minimum of 9 to a maximum of 23. The number of gap junctions on a branch of a dendritic tree varied from 1-9. For all 7 neurons the closest gap junction was located .apprx. 65 .mu.m from the soma and the furthest 280 .mu.m from the soma. When gap junction position was plotted as a function of electrotonic distance from the soma, the variability in their distribution decreased significantly. Synaptic location was on average .apprx. 0.5 space constants from the soma, and this value compared favorably with that determined from an analysis of half-width and rise time of the electrotonic synaptic potential for these neurons. Results suggest that the presynaptic axon tends to make, on average, synaptic contact at the same electrical distance from the soma.