Descending Axonal Projections from the Inferior Colliculus Target Nearly All Excitatory and Inhibitory Cell Types of the Dorsal Cochlear Nucleus
Descending Axonal Projections from the Inferior Colliculus Target Nearly All Excitatory and Inhibitory Cell Types of the Dorsal Cochlear Nucleus
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DOI：
10.1523/jneurosci.1190-21.2022
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发表时间：
2022-04-20
影响因子：
5.3
通讯作者：
Trussell, Laurence O.
中科院分区：
文献类型：
--
作者：
Balmer, Timothy S.;Trussell, Laurence O.
耳蜗背核(DCN)整合了听神经输入和非听觉感觉信号，被认为具有声源定位和抑制自发性声音的功能。DCN还整合了来自下行听觉通路的活动，包括来自DCN的主要上行靶点--下丘的一个特别大的反馈投射。要了解这些下行反馈信号是如何整合到DCN电路中的，以及它们在听力中扮演的角色，需要知道目标DCN细胞类型及其突触后反应。为了探索这些问题，在雄性和雌性小鼠身上，用跨突触病毒方法标记了从IC接受下行突触输入的DCN中的神经元，这使得它们能够成为急性脑片全细胞记录的靶点。我们测试了它们对IC下行投射的光遗传激活的突触反应。颗粒细胞域中的每一种细胞类型都接受来自IC的单突触谷氨酸能输入，这表明该区域被认为是非听觉感觉输入的整合区域，也处理听觉输入，可能在听力中具有复杂而被低估的作用。此外，我们发现颗粒细胞区以外的DCN细胞类型也接收下行IC信号，包括主投射神经元以及抑制它们的神经元，导致一种可能通过反馈兴奋和侧抑制而锐化调谐的电路。
The dorsal cochlear nucleus (DCN) integrates auditory nerve input with nonauditory sensory signals and is proposed to function in sound source localization and suppression of self-generated sounds. The DCN also integrates activity from descending auditory pathways, including a particularly large feedback projection from the inferior colliculus (IC), the main ascending target of the DCN. Understanding how these descending feedback signals are integrated into the DCN circuit and what role they play in hearing requires knowing the targeted DCN cell types and their postsynaptic responses. In order to explore these questions, neurons in the DCN that received descending synaptic input from the IC were labeled with a trans-synaptic viral approach in male and female mice, which allowed them to be targeted for whole-cell recording in acute brain slices. We tested their synaptic responses to optogenetic activation of the descending IC projection. Every cell type in the granule cell domain received monosynaptic, glutamatergic input from the IC, indicating that this region, considered an integrator of nonauditory sensory inputs, processes auditory input as well and may have complex and underappreciated roles in hearing. Additionally, we found that DCN cell types outside the granule cell regions also receive descending IC signals, including the principal projection neurons, as well as the neurons that inhibit them, leading to a circuit that may sharpen tuning through feedback excitation and lateral inhibition.