The Calyx of Held Develops Adult-Like Dynamics and Reliability by Hearing Onset in the Mouse In Vivo
The Calyx of Held Develops Adult-Like Dynamics and Reliability by Hearing Onset in the Mouse In Vivo
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DOI：
10.1523/jneurosci.0575-11.2011
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发表时间：
2011-05-04
影响因子：
5.3
通讯作者：
Ruebsamen, Rudolf
中科院分区：
文献类型：
--
作者：
Sonntag, Mandy;Englitz, Bernhard;Ruebsamen, Rudolf
自从发现了听觉前哺乳动物的模式化自发活动机制以来，听觉系统的发育受到越来越多的关注。这种早期活动起源于耳蜗，被认为对于听觉系统中突触连接的建立和完善非常重要。在本研究中，我们研究突触传递及其与发育中的听觉系统中自发放电的相互作用。我们使用 Held 的花萼作为模型系统，可以在广泛的年龄范围 [出生后第 8 天 (P8)-P28] 体内研究这个问题。为了精确量化突触传递的时间和可靠性，我们开发了一种新颖的拟合方法，将细胞外记录的信号分解为其突触前和突触后成分。在预听小鼠中，我们发现信号传输不可靠，传输延迟和突触后成分的幅度具有很大的可变性。这些时间和幅度的变化与之前的活动密切相关。在听力开始时（P12-P14），信号传输特性收敛到类似成人的状态，其特点是传输可靠性高、时序和幅度一致性高。尽管动作电位中仍然存在活动依赖性抑制，但 EPSP 抑制不再发挥突出作用。总之，Held 花萼处突触传递的成熟似乎是精确定时的，以便在声诱发信号处理开始时实现其成年潜力。
The development of the auditory system has received increasing attention since the mechanisms of patterned, spontaneous activity in prehearing mammals were discovered. This early activity originates in the cochlea and is assumed to be of importance for the establishment and refinement of synaptic connections in the auditory system. In the present study we investigate synaptic transmission and its interplay with spontaneous discharges in the developing auditory system. We used the calyx of Held as a model system, where this question can be investigated in vivo over a broad range of ages [postnatal day 8 (P8)-P28]. To precisely quantify the timing and reliability of synaptic transmission, we developed a novel fitting approach which decomposes the extracellularly recorded signal into its presynaptic and postsynaptic components. In prehearing mice, we found signal transmission to be unreliable, with high variability in the transmission delay and in the amplitude of postsynaptic components. These timing and amplitude changes were strongly correlated with the preceding activity. Around hearing onset (P12-P14), the properties of signal transmission converged to the adult-like state which was characterized by high transmission reliability as well as high consistency in timing and amplitude. Although activity-dependent depression was still found in action potentials, EPSP depression no longer played a prominent role. In conclusion, the maturation of synaptic transmission at the calyx of Held seems to be precisely timed to achieve its adult potential by the time acoustically evoked signal processing commences.