Quantal amplitude and quantal variance of strontium-induced asynchronous EPSCs in rat dentate granule neurons
Quantal amplitude and quantal variance of strontium-induced asynchronous EPSCs in rat dentate granule neurons
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DOI：
10.1111/j.1469-7793.1999.227aa.x
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发表时间：
1999-04-01
影响因子：
5.5
通讯作者：
Clements, JD
中科院分区：
文献类型：
--
作者：
Bekkers, JM;Clements, JD
1. 在17- 21日龄大鼠（22-25℃）的急性切片中，使用组织切割和最小的细胞外刺激选择性地激活少量突触接触，记录了齿状回颗粒细胞的兴奋性突触后电流（EPSCs）。在外部溶液中加入毫摩尔的Sr2+，产生了在刺激后持续数百毫秒的异步EPSCs （aEPSCs）。最小刺激aEPSCs类似于在同一细胞中记录的微型EPSCs (mEPSCs)，但在mEPSCs经历的更大范围的树突过滤方面与它们不同。aEPSCs与同步EPSCs （sEPSCs）具有相同的刺激阈值，同步EPSCs在刺激后具有短暂的潜伏期。远端输入刺激后的aEPSCs平均上升时间比近端输入刺激后的aEPSCs慢。这些结果表明，aEPSCs起源于产生sepscs的相同突触。近端诱导的aEPSCs在-70 mV下的平均振幅为6.7 +/- 2.2 pA （+/- sd, n = 23个细胞），振幅变化系数为0.46 +/- 0.08.4。sEPSCs的振幅分布没有明显的峰值。对aEPSC振幅分布形状的蒙特卡罗模型表明，我们的数据最好用量子方差的场内模型来解释。结果表明，Sr2+诱发的aEPSCs是在最近受到动作电位侵袭的突触末端发生的独特事件，因此可以提供这些末端量子振幅和量子方差的直接信息。在这类兴奋性突触中，大的量子方差模糊了被诱发sEPSCs振幅的量化。
1. Excitatory postsynaptic currents (EPSCs) were recorded from granule cells of the dentate gyrus in acute slices of 17- to 21-day-old rats (22-25 degrees C) using tissue cuts and minimal extracellular stimulation to selectively activate a small number of synaptic contacts.2. Adding millimolar Sr2+ to the external solution produced asynchronous EPSCs (aEPSCs) lasting for several hundred milliseconds after the stimulus. Minimally stimulated aEPSCs resembled miniature EPSCs (mEPSCs) recorded in the same cell but differed from them in ways expected from the greater range of dendritic filtering experienced by mEPSCs. aEPSCs had the same stimulus threshold as the synchronous EPSCs (sEPSCs) that followed the stimulus with a brief latency. aEPSCs following stimulation of distal inputs had a slower mean rise time than those following stimulation of proximal inputs. These results suggest that aEPSCs arose from the same synapses that generated sEPSCs.3. Proximally elicited aEPSCs had a mean amplitude of 6.7 +/- 2.2 pA (+/- S.D., n = 23 cells) at -70 mV and an amplitude coefficient of variation of 0.46 +/- 0.08.4. The amplitude distributions of sEPSCs never exhibited distinct peaks.5. Monte Carlo modelling of the shapes of aEPSC amplitude distributions indicated that our data were best explained by an intrasite model of quantal variance.6. It is concluded that Sr2+-evoked aEPSCs are uniquantal events arising at synaptic terminals that were recently invaded by an action potential, and so provide direct information about the quantal amplitude and quantal variance at those terminals. The large quantal variance obscures quantization of the amplitudes of evoked sEPSCs at this class of excitatory synapse.