Inhibitory NPY Neurons Provide a Large and Heterotopic Commissural Projection in the Inferior Colliculus.
Inhibitory NPY Neurons Provide a Large and Heterotopic Commissural Projection in the Inferior Colliculus.
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DOI：
10.3389/fncir.2022.871924
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发表时间：
2022
影响因子：
3.5
通讯作者：
Roberts, Michael T.
中科院分区：
文献类型：
--
作者：
Anair, Justin D.;Silveira, Marina A.;Mirjalili, Pooyan;Beebe, Nichole L.;Schofield, Brett R.;Roberts, Michael T.
下丘（IC）位于中脑，在许多听觉计算中起着重要作用，包括语音处理和声音定位。IC的左右两侧通过密集的纤维束相互连接，即IC的连接（CoIC），为每个IC提供其最大的输入源之一（即对侧IC）。尽管它声名显赫，但人们对CoIC仍知之甚少。先前使用顺行和逆行束示踪的研究表明，IC互交投射主要是同位和异位的，目标是对侧IC相同频率区域的镜像位置。然而，尚不清楚特定类别的神经元，特别是占互交投射约10%-40%的抑制性神经元是否遵循这种模式。因此，我们研究了神经肽Y （NPY）神经元的互交投射，这是IC中第一类分子可识别的gaba能神经元。在雌雄小鼠NPY- hrgfp中使用逆转录珠（RB）逆行追踪，我们发现NPY神经元占互交投射的11%。此外，局灶注射Retrobeads显示，IC中央核的NPY神经元比非NPY神经元表现出更发散和异位的互交投射模式。因此，互交NPY神经元被定位为对侧IC提供侧抑制。通过这个回路，驱动一侧IC有限区域活动的声音可能会抑制对侧IC更广泛区域的活动。
Located in the midbrain, the inferior colliculus (IC) plays an essential role in many auditory computations, including speech processing and sound localization. The right and left sides of the IC are interconnected by a dense fiber tract, the commissure of the IC (CoIC), that provides each IC with one of its largest sources of input (i.e., the contralateral IC). Despite its prominence, the CoIC remains poorly understood. Previous studies using anterograde and retrograde tract-tracing showed that IC commissural projections are predominately homotopic and tonotopic, targeting mirror-image locations in the same frequency region in the contralateral IC. However, it is unknown whether specific classes of neurons, particularly inhibitory neurons which constitute ~10%–40% of the commissural projection, follow this pattern. We, therefore, examined the commissural projections of Neuropeptide Y (NPY) neurons, the first molecularly identifiable class of GABAergic neurons in the IC. Using retrograde tracing with Retrobeads (RB) in NPY-hrGFP mice of both sexes, we found that NPY neurons comprise ~11% of the commissural projection. Moreover, focal injections of Retrobeads showed that NPY neurons in the central nucleus of the IC exhibit a more divergent and heterotopic commissural projection pattern than non-NPY neurons. Thus, commissural NPY neurons are positioned to provide lateral inhibition to the contralateral IC. Through this circuit, sounds that drive activity in limited regions on one side of the IC likely suppress activity across a broader region in the contralateral IC.
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