Laboratory for the Neurobiology of Hearing, Neuroscience Institute of Castilla y León, University of Salamanca Salamanca, Spain.
Front Neuroanat. 2011 Feb 22;5:1. doi: 10.3389/fnana.2011.00001. eCollection 2011.
The superior paraolivary nucleus (SPON), a prominent GABAergic center of the mammalian auditory brainstem, projects to the ipsilateral inferior colliculus (IC) and sends axons through the commissure of the IC (CoIC). Herein we demonstrate that the SPON is reciprocally connected with the recently discovered tectal longitudinal column (TLC). The TLC is a long and narrow structure that spans nearly the entire midbrain tectum longitudinally, immediately above the periaqueductal gray matter (PAG) and very close to the midline. Unilateral injections of biotinylated dextran into the SPON of the rat label abundant terminal fibers in the TLC of both sides, with an ipsilateral predominance. The SPON provides a dense innervation of the entire rostrocaudal extent of the ipsilateral TLC, and a relatively sparser innervation of the caudal and rostral portions of the contralateral TLC. SPON fibers reach the TLC by two routes: as collaterals of axons of the CoIC, and as axons that circumvent the ipsilateral IC before traveling in the deep layers of the superior colliculus (SC). The density of these projections identifies SPON as a significant source of input to the TLC. Other targets of the SPON discovered in this study include the deep layers of the SC and the PAG. The same experiments reveal numerous labeled cell bodies in the TLC, interspersed among the labeled SPON fibers. This observation suggests that the SPON is a significant target of TLC projections. The discovery of novel reciprocal connections between the SPON and the TLC opens unexpected avenues for investigation of sound processing in mammalian brainstem circuits.
上橄榄核（SPON）是哺乳动物听觉脑干中的一个突出的 GABA 能中心，投射到同侧下丘（IC），并通过 IC 联合（CoIC）发送轴突。本文证明 SPON 与最近发现的顶盖纵列（TLC）之间存在相互联系。TLC 是一个长而窄的结构，几乎横跨整个中脑顶盖纵向，位于脑水管周围灰质（PAG）上方，并非常接近中线。将生物素化葡聚糖单侧注入大鼠的 SPON 中，可标记双侧 TLC 中大量的终末纤维，以同侧为主。SPON 对同侧 TLC 的整个前后范围提供密集的神经支配，对同侧 TLC 的尾端和前端提供相对稀疏的神经支配。SPON 纤维通过两条途径到达 TLC：作为 CoIC 轴突的侧支，以及在穿过同侧 IC 后在顶盖上层（SC）深层行进的轴突。这些投射的密度表明 SPON 是 TLC 的重要输入源。本研究中发现的 SPON 的其他靶点包括 SC 的深层和 PAG。同样的实验揭示了 TLC 中存在大量标记的细胞体，散布在标记的 SPON 纤维之间。这一观察结果表明 SPON 是 TLC 投射的重要靶点。SPON 和 TLC 之间发现新的相互联系，为研究哺乳动物脑干回路中的声音处理开辟了意想不到的途径。
