Single spine Ca2+ signals evoked by coincident EPSPs and backpropagating action potentials in spiny stellate cells of layer 4 in the juvenile rat somatosensory barrel cortex
Single spine Ca2+ signals evoked by coincident EPSPs and backpropagating action potentials in spiny stellate cells of layer 4 in the juvenile rat somatosensory barrel cortex
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DOI：
10.1523/jneurosci.3332-03.2004
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发表时间：
2004-02-18
影响因子：
5.3
通讯作者：
Sakmann, B
中科院分区：
文献类型：
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作者：
Nevian, T;Sakmann, B
突触前和突触后活动的精确时间会导致突触的改变，这依赖于钙离子的内流。用双光子激发显微镜研究了幼年大鼠丘脑脑片躯体感觉桶皮质第四层(L4)棘神经元棘突的[Ca~(2+)]瞬变，以确定突触前和突触后准一致活动中钙信号的峰时依赖性。反向传播动作电位(BAP)诱发的[Ca~(2+)]瞬变是由电压依赖性钙通道介导的，并且在脊髓和邻近的树突干中具有类似的大小。随着脊椎距小体的距离增加，它们逐渐减少。EPSP诱发的[Ca~(2+)]瞬变仅限于脊椎头部，几乎完全由NMDAR(NMDAR)介导的Ca~(2+)内流。其波幅与棘沿树枝的位置无关。当EPSP和BaP在大约50毫秒的时间窗口内发生时，BAPS与EPSP相互作用，在脊柱中产生次线性或超线性的钙信号。突触刺激与BaP同时引起大量突触后钙内流，这种内流仅限于单个脊椎，即使在EPSP被AMPA受体拮抗剂NBQX阻断后也是如此，NBQX使突触有效地“电沉默”。我们得出结论，L4细胞的脊椎可以作为敏锐的调谐检测器，检测L4细胞的传入和L4细胞树突的脊椎中发生的AP模式。近乎一致的突触前和突触后AP的读数是在树突BaP过程中NMDARs的短暂解锁介导的大量瞬时钙离子流入突触活性脊椎。
The precise timing of presynaptic and postsynaptic activity results in synaptic modifications, which depend on calcium influx. [Ca2+] transients in the spines of spiny neurons in layer 4 (L4) of the somatosensory barrel cortex of young rats were investigated in thalamocortical brain slices by two-photon excitation microscopy to determine the spike timing dependence of the Ca2+ signal during near-coincident presynaptic and postsynaptic activity. [Ca2+] transients evoked by backpropagating action potentials (bAPs) were mediated by voltage-dependent Ca2+ channels and were of comparable size in a spine and adjacent dendritic shaft. They decreased with the distance of the spine from the soma. EPSP-evoked [Ca2+] transients were restricted to spine heads and were mediated almost entirely by Ca2+ influx through NMDA receptors (NMDARs). Their amplitude was independent of the position of the spine along the dendritic arbor. bAPs interacted with EPSPs to generate sublinear or supralinear Ca2+ signals in a spine when EPSP and bAP occurred within a time window of similar to50 msec. Synaptic stimulation, coincident with a bAP, evoked a large postsynaptic Ca2+ influx that was restricted to a single spine, even after EPSPs were blocked by the AMPA receptor antagonist NBQX that rendered synapses effectively "electrically silent."We conclude that the spines of L4 cells can act as sharply tuned detectors for patterns of APs occurring in the boutons of the afferents to L4 cells and the spines of L4 cell dendrites. The readout for near-coincident presynaptic and postsynaptic APs is a large transient Ca2+ influx into synaptically active spines mediated by the brief unblocking of NMDARs during the dendritic bAP.