School of Biomedical Sciences, Kent State University, Kent, OH United States; Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Rootstown, OH, United States.
Department of Anatomy and Neurobiology, Hearing Research Group, Northeast Ohio Medical University, Rootstown, OH, United States.
Hear Res. 2021 Nov;411:108352. doi: 10.1016/j.heares.2021.108352. Epub 2021 Sep 20.
Cholinergic axons from the pedunculopontine tegmental nucleus (PPT) innervate the inferior colliculus where they are positioned to modulate both excitatory and inhibitory circuits across the central nucleus and adjacent cortical regions. More rostral regions of the auditory midbrain include the nucleus of the brachium of the inferior colliculus (NBIC), the intercollicular tegmentum (ICt) and the rostral pole of the inferior colliculus (ICrp). These regions appear especially important for multisensory integration and contribute to orienting behavior and many aspects of auditory perception. These regions appear to receive cholinergic innervation but little is known about the distribution of cholinergic axons in these regions or the cells that they contact. The present study used immunostaining to examine the distribution of cholinergic axons and then used chemically-specific viral tracing to examine cholinergic projections from the PPT to the intercollicular areas in male and female transgenic rats. Staining with antibodies against vesicular acetylcholine transporter revealed dense cholinergic innervation throughout the NBIC, ICt and ICrp. Deposits of viral vector into the PPT labeled cholinergic axons bilaterally in the NBIC, ICt and ICrp. In each area, the projections were denser on the ipsilateral side. The axons appeared morphologically similar across the three areas. In each area, en passant and terminal boutons from these axons appeared in the neuropil and also in close apposition to cell bodies. Immunostaining with a marker for GABAergic cells suggested that the cholinergic axons likely contact both GABAergic and non-GABAergic cells in the NBIC, ICt and ICrp. Thus, the cholinergic axons could affect multisensory processing by modulating excitatory and inhibitory circuits in the NBIC, ICt and ICrp. The similarity of axons and their targets suggests there may be a common function for cholinergic innervation across the three areas. Given what is known about the PPT, such functions could be associated with arousal, sleep-wake cycle, reward and plasticity.
来自脑桥被盖脚核（PPT）的胆碱能轴突支配下丘，它们位于中央核和相邻皮质区域的兴奋性和抑制性回路之间，处于调节位置。听觉中脑的更前区域包括下丘臂核（NBIC）、中脑下丘间核（ICt）和下丘前极（ICrp）。这些区域似乎对多感觉整合特别重要，并有助于定向行为和听觉感知的许多方面。这些区域似乎接受胆碱能支配，但对这些区域中的胆碱能轴突分布或它们接触的细胞知之甚少。本研究使用免疫染色检查胆碱能轴突的分布，然后使用化学特异性病毒追踪检查 PPT 到雄性和雌性转基因大鼠的间脑区域的胆碱能投射。针对囊泡乙酰胆碱转运蛋白的抗体染色显示 NBIC、ICt 和 ICrp 中存在密集的胆碱能神经支配。将病毒载体沉积到 PPT 中会在 NBIC、ICt 和 ICrp 中双侧标记胆碱能轴突。在每个区域，同侧的投射密度更大。这些轴突在三个区域的形态相似。在每个区域，来自这些轴突的顺行和终末末梢出现在神经胶质中，并且与细胞体紧密接触。用 GABA 能细胞标志物进行免疫染色表明，胆碱能轴突可能与 NBIC、ICt 和 ICrp 中的 GABA 能和非 GABA 能细胞接触。因此，胆碱能轴突可以通过调节 NBIC、ICt 和 ICrp 中的兴奋性和抑制性回路来影响多感觉处理。轴突和其靶标之间的相似性表明，胆碱能支配在三个区域之间可能具有共同的功能。鉴于对 PPT 的了解，这些功能可能与觉醒、睡眠-觉醒周期、奖励和可塑性有关。
