Depletion of calcium in the synaptic cleft of a calyx-type synapse in the rat brainstem
Depletion of calcium in the synaptic cleft of a calyx-type synapse in the rat brainstem
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DOI：
10.1111/j.1469-7793.1999.00123.x
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发表时间：
1999-11-15
影响因子：
5.5
通讯作者：
Sakmann, B
中科院分区：
文献类型：
--
作者：
Borst, JGG;Sakmann, B
1. 在大鼠听性脑干切片中，对大突触前末梢、Held 细胞盏和突触后细胞、梯形体内侧核 (MNTB) 的主要细胞进行电压钳记录时，观察到一种新形式的兴奋性突触传递的突触抑制。2.突触后细胞短暂（100 ms）去极化至 0 mV 使 EPSC 的振幅降低 35 +/- 5% (n = 7)，在去极化后 10 ms 时测量。 0.5 s.3 内恢复。 EPSC 的减少很可能是由于突触前钙流入减少，因为突触后去极化减少了突触前钙或钡电流。相反，在递质释放最少的情况下，突触前去极化也减少了突触后钙或钡的流入。4。钙电流和突触后去极化诱导的突触传递抑制在相似的时间过程中恢复，表明这种形式的突触抑制很可能是由于突触间隙中 Ca2+ 的耗尽所致。5。我们得出的结论是，当突触前或突触后细胞的 Ca2+ 大量流入时，细胞外 Ca2+ 就会耗尽。在这些条件下，突触间隙中的 Ca2+ 浓度是突触活性水平的敏感指标。然而，突触间隙对 Ca2+ 消耗的敏感度低于根据其估计体积预测的敏感度。
1. A new form of synaptic depression of excitatory synaptic transmission was observed when making voltage-clamp recordings from large presynaptic terminals, the calyces of Held and postsynaptic cells, the principal cells of the medial nucleus of the trapezoid body (MNTB), in slices of the rat auditory brainstem.2. A short (100 ms) depolarization of the postsynaptic cell to 0 mV reduced the amplitude of the EPSCs by 35 +/- 5% (n = 7), measured at 10 ms following the depolarization. Recovery occurred within 0.5 s.3. The reduction of the EPSCs was most probably due to reduced presynaptic calcium influx, since postsynaptic depolarization reduced presynaptic calcium or barium currents. Conversely, presynaptic depolarization also reduced postsynaptic calcium or barium influx, under conditions where transmitter release was minimal.4. The calcium currents and the postsynaptic depolarization-induced suppression of synaptic transmission recovered with a similar time course, suggesting that this form of synaptic depression was, most probably, due to depletion of Ca2+ in the synaptic cleft.5. We conclude that when the Ca2+ influx into the pre- or postsynaptic cell is large, extracellular Ca2+ is depleted. Under these conditions, the Ca2+ concentration in the synaptic cleft is a sensitive indicator of the level of synaptic activity. However, the synaptic cleft is less sensitive to Ca2+ depletion than predicted from its estimated volume.