Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.
Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California, USA.
J Comp Neurol. 2024 Nov;532(11):e25683. doi: 10.1002/cne.25683.
The control of the respiratory rhythm and airway motor activity is essential for life. Accumulating evidence indicates that the postinspiratory complex (PiCo) is crucial for generating behaviors that occur during the postinspiratory phase, including expiratory laryngeal activity and swallowing. Located in the ventromedial medulla, PiCo is defined by neurons co-expressing two neurotransmitter markers (ChAT and Vglut2/Slc17a6). Here, we mapped the input-output connections of these neurons using viral tracers and intersectional viral-genetic tools. PiCo neurons were specifically targeted by focal injection of a doubly conditional Cre- and FlpO-dependent AAV8 viral marker (AAV8-Con/Fon-TVA-mCherry) into the left PiCo of adult Chat: Vglut2 mice, for anterograde axonal tracing. These experiments revealed projections to various brain regions, including the Cu, nucleus of the solitary tract (NTS), Amb, X, XII, Sp5, RMg, intermediate reticular nucleus (IRt), lateral reticular nucleus (LRt), pre-Bötzinger complex (preBötC), contralateral PiCo, laterodorsal tegmental nucleus (LDTg), pedunculopontine tegmental nucleus (PPTg), periaqueductal gray matter (PAG), Kölliker-Fuse (KF), PB, and external cortex of the inferior colliculus (ECIC). A rabies virus (RV) retrograde transsynaptic approach was taken with EnvA-pseudotyped G-deleted (RV-SAD-G-GFP) to similarly target PiCo neurons in Chat: Vglut2 mice, following prior injections of helper AAVs (a mixture of AAV-Ef1a-Con/Fon oG and viral vector AAV8-Con/Fon-TVA-mCherry). This combined approach revealed prominent synaptic inputs to PiCo neurons from NTS, IRt, and A1/C1. Although PiCo neurons project axons to the contralateral PiCo area, this approach did not detect direct contralateral connections. We suggest that PiCo serves as a critical integration site, projecting and receiving neuronal connections implicated in breathing, arousal, swallowing, and autonomic regulation.
呼吸节律和气道运动活动的控制对生命至关重要。越来越多的证据表明，吸气后复合波（PiCo）对于产生吸气后阶段发生的行为至关重要，包括喉外呼气活动和吞咽。PiCo 位于腹内侧延髓，由共表达两种神经递质标志物（ChAT 和 Vglut2/Slc17a6）的神经元定义。在这里，我们使用病毒示踪剂和交叉病毒遗传工具来绘制这些神经元的输入-输出连接。通过将双条件 Cre 和 FlpO 依赖性 AAV8 病毒标记物（AAV8-Con/Fon-TVA-mCherry）聚焦注射到成年 Chat:Vglut2 小鼠的左侧 PiCo 中，专门靶向 PiCo 神经元，用于顺行轴突追踪。这些实验揭示了向包括 Cu、孤束核（NTS）、Amb、X、XII、Sp5、RMg、中间网状核（IRt）、外侧网状核（LRt）、pre-Bötzinger 复合体（preBötC）、对侧 PiCo、外侧背侧被盖核（LDTg）、pedunculopontine 被盖核（PPTg）、导水管周围灰质（PAG）、Kölliker-Fuse（KF）、PB 和下丘外侧皮质（ECIC）等各种脑区的投射。采用狂犬病病毒（RV）逆行转导突触方法，用 EnvA-假型化 G 缺失（RV-SAD-G-GFP）靶向 Chat:Vglut2 小鼠中的 PiCo 神经元，此前先注射辅助 AAV（AAV-Ef1a-Con/Fon oG 和病毒载体 AAV8-Con/Fon-TVA-mCherry 的混合物）。这种联合方法揭示了 NTS、IRt 和 A1/C1 对 PiCo 神经元的显著突触输入。尽管 PiCo 神经元向对侧 PiCo 区域投射轴突，但该方法未检测到直接的对侧连接。我们认为 PiCo 作为一个关键的整合位点，投射和接收与呼吸、觉醒、吞咽和自主调节有关的神经元连接。
