SYNAPTIC TRANSMISSION - ION CONCENTRATION CHANGES IN THE SYNAPTIC CLEFT
SYNAPTIC TRANSMISSION - ION CONCENTRATION CHANGES IN THE SYNAPTIC CLEFT
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DOI：
10.1098/rspb.1979.0095
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发表时间：
1979-01-01
期刊：
影响因子：
--
通讯作者：
ILES, JF
中科院分区：
文献类型：
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作者：
ATTWELL, D;ILES, JF
电流流过活动突触的突触后膜，会改变突触间隙中的离子浓度。已发表的实验数据被用来预测：在青蛙神经肌肉接头的突触间隙中的Na和K浓度的变化;在猫运动神经元上的Ia突触扣下的间隙中的Na耗尽。在两个突触处预测显著的浓度变化。这些变化应有助于观察到的电流的时间依赖性，并应导致电流的反转电位与时间相关。在蛙神经肌肉接头处，终板电流的时间过程先前被示出取决于流动的电流的大小（在给定的电位下）。这是由于裂缝离子浓度的变化。我们预测的神经肌肉接头终板电流反转电位的时间依赖性变化可能太小而无法检测到。这是因为Na的耗尽和K的积累对反转电位的影响几乎抵消。在反向电位附近，应保持复杂时程的小电流，即，不存在真正的反转电势。这种电流以前曾在实验中观察到。在猫Ia突触，突触电流应该耗尽一个显着的分数可用的细胞外钠离子。因此，突触电流的大小应该是相对独立的激活的突触后通道的数量和膜电位，如先前实验发现的。
Currents flowing through the postsynaptic membrane of an active synapse will tend to change the concentrations of ions in the synaptic cleft. Published experimental data are used to predict: the Na and K concentration changes in the synaptic cleft at the frog neuromuscular junction; the Na depletion in the cleft under a Ia synaptic bouton on a cat motor neuron. Significant concentration changes are predicted at both synapses. These changes should contribute to the time dependence of the observed current and should cause the reversal potential of the current to be time dependent. At the frog neuromuscular junction, the time course of the end plate current was shown previously to depend on the magnitude of the current flowing (at a given potential). This is attributed to changes of the cleft ion concentration. The time dependent changes of the end plate current reversal potential that we predict for the neuromuscular junction are probably too small to be detected. This is because the effects of Na depletion and K accumulation on the reversal potential almost cancel. Near the reversal potential small currents of complex time course should remain, i.e., no true reversal potential exits. Such currents were previously seen experimentally. At the cat Ia synapse, the synaptic current should deplete a significant fraction of the available extracellular Na ions. Consequently, the magnitude of the synaptic current should be relatively independent of the number of postsynaptic channels activated and of the membrane potential, as was previously found experimentally.