The inferior colliculus processes nearly all ascending auditory information. Most collicular cells respond to sound, and for a majority of these cells, the responses can be modulated by acetylcholine (ACh). The cholinergic effects are varied and, for the most part, the underlying mechanisms are unknown. The major source of cholinergic input to the inferior colliculus is the pedunculopontine tegmental nucleus (PPT), part of the pontomesencephalic tegmentum known for projections to the thalamus and roles in arousal and the sleep-wake cycle. Characterization of PPT inputs to the inferior colliculus has been complicated by the mixed neurotransmitter population within the PPT. Using selective viral-tract tracing techniques in a ChAT-Cre Long Evans rat, the present study characterizes the distribution and targets of cholinergic projections from PPT to the inferior colliculus. Following the deposit of viral vector in one PPT, cholinergic axons studded with boutons were present bilaterally in the inferior colliculus, with the greater density of axons and boutons ipsilateral to the injection site. On both sides, cholinergic axons were present throughout the inferior colliculus, distributing boutons to the central nucleus, lateral cortex, and dorsal cortex. In each inferior colliculus (IC) subdivision, the cholinergic PPT axons appear to contact both GABAergic and glutamatergic neurons. These findings suggest cholinergic projections from the PPT have a widespread influence over the IC, likely affecting many aspects of midbrain auditory processing. Moreover, the effects are likely to be mediated by direct cholinergic actions on both excitatory and inhibitory circuits in the inferior colliculus.

中文翻译：

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来自桥脚被盖核的胆碱能投射接触下丘中的兴奋性和抑制性神经元。


下丘处理几乎所有上行听觉信息。大多数丘细胞对声音有反应，并且对于大多数这些细胞来说，反应可以通过乙酰胆碱 (ACh) 来调节。胆碱能作用多种多样，而且大多数情况下，其潜在机制尚不清楚。下丘胆碱能输入的主要来源是桥脚被盖核（PPT），它是桥脑中脑被盖的一部分，以投射到丘脑并在觉醒和睡眠-觉醒周期中发挥作用而闻名。由于 PPT 内混合的神经递质群，对下丘的 PPT 输入的表征变得复杂。本研究利用 ChAT-Cre Long Evans 大鼠的选择性病毒道追踪技术，描述了从 PPT 到下丘的胆碱能投射的分布和目标。在一份 PPT 中沉积病毒载体后，下丘两侧均出现布满布顿的胆碱能轴突，注射部位同侧的轴突和布顿密度更大。在两侧，胆碱能轴突遍布整个下丘，将布顿分布到中央核、外侧皮质和背侧皮质。在每个下丘 (IC) 细分中，胆碱能 PPT 轴突似乎同时接触 GABA 能和谷氨酸能神经元。这些发现表明 PPT 的胆碱能投射对 IC 具有广泛的影响，可能影响中脑听觉处理的许多方面。此外，这些作用可能是通过对下丘的兴奋性和抑制性回路的直接胆碱能作用来介导的。