Tonotopic Specializations in Number, Size, and Reversal Potential of GABAergic Inputs Fine-Tune Temporal Coding at Avian Cochlear Nucleus
Tonotopic Specializations in Number, Size, and Reversal Potential of GABAergic Inputs Fine-Tune Temporal Coding at Avian Cochlear Nucleus
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DOI：
10.1523/jneurosci.0884-21.2021
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发表时间：
2021-10-27
影响因子：
5.3
通讯作者：
Kuba, Hiroshi
中科院分区：
文献类型：
--
作者：
Al-Yaari, Mohammed;Onogi, Chikao;Kuba, Hiroshi
神经元中的GABA能抑制在决定神经回路的输出中起关键作用。鸟类大细胞核（NM）中的神经元使用几种音调区域依赖性特化来将听觉神经中的声音定时信息传递到高级听觉核团。以前，我们表明，前馈GABA能抑制在NM有不同的依赖于听觉神经活动的水平，与低频区具有低阈值和线性关系，而高频区具有高阈值和阶梯状的关系。然而，目前还不清楚GABA能突触是如何调节和相互作用的其他专业的NM神经元。在这项研究中，我们研究了GABA能传输的NM鸡的性别和探讨其贡献的时间编码的声音在每个tonotopic区域。我们发现，单位GABA能电流的数量和大小及其逆转电位在NM的每个tonotopic区域微调。在低频区，单位GABA能电流的数量较大，但规模较小。此外，它们的逆转电位接近神经元的静息电位，这使得尽管钾电导较小，但仍能够可靠地抑制。另一方面，在高频区域，单位GABA能电流较少，较大，且高度去极化，这通过激活大的钾电导实现了强大的抑制。因此，我们认为GABA能突触与兴奋性突触和突触后神经元的特性相协调，确保了宽频率和强度范围的时间编码。
GABAergic inhibition in neurons plays a critical role in determining the output of neural circuits. Neurons in avian nucleus magnocellularis (NM) use several tonotopic-region-dependent specializations to relay the timing information of sound in the auditory nerve to higher auditory nuclei. Previously, we showed that feedforward GABAergic inhibition in NM has a different dependence on the level of auditory nerve activity, with the low-frequency region having a low-threshold and linear relationship, while the high-frequency region has a high-threshold and step-like relationship. However, it remains unclear how the GABAergic synapses are tonotopically regulated and interact with other specializations of NM neurons. In this study, we examined GABAergic transmission in the NM of chickens of both sexes and explored its contributions to the temporal coding of sound at each tonotopic region. We found that the number and size of unitary GABAergic currents and their reversal potential were finely tuned at each tonotopic region in the NM. At the lower-frequency region, unitary GABAergic currents were larger in number but smaller in size. In addition, their reversal potential was close to the resting potential of neurons, which enabled reliable inhibition despite the smaller potassium conductance. At the higher-frequency region, on the other hand, unitary GABAergic currents were fewer, larger, and highly depolarizing, which enabled powerful inhibition via activating the large potassium conductance. Thus, we propose that GABAergic synapses are coordinated with the characteristics of excitatory synapses and postsynaptic neurons, ensuring the temporal coding for wide frequency and intensity ranges.